Merge pull request #657 from secondlife/DRTVWR-592

Merge PBR terrain and put PBR terrain behind feature flag.

38 files changed, 2247 insertions, 312 deletions

diff --git a/indra/llimage/llimage.cpp b/indra/llimage/llimage.cpp
index 031471d1fe..acfc254b65 100644
--- a/indra/llimage/llimage.cpp
+++ b/indra/llimage/llimage.cpp
@@ -31,6 +31,7 @@
 
 #include "llmath.h"
 #include "v4coloru.h"
+#include "v3color.h"
 
 #include "llimagebmp.h"
 #include "llimagetga.h"
@@ -1026,6 +1027,34 @@ bool LLImageRaw::optimizeAwayAlpha()
     return false;
 }
 
+bool LLImageRaw::makeAlpha()
+{
+    if (getComponents() == 3)
+    {
+        U8* data = getData();
+        U32 pixels = getWidth() * getHeight();
+
+        // alpha channel doesn't exist, make a new copy of data with alpha channel
+        U8* new_data = (U8*) ll_aligned_malloc_16(getWidth() * getHeight() * 4);
+
+        for (U32 i = 0; i < pixels; ++i)
+        {
+            U32 di = i * 4;
+            U32 si = i * 3;
+            for (U32 j = 0; j < 3; ++j)
+            {
+                new_data[di+j] = data[si+j];
+            }
+        }
+
+        setDataAndSize(new_data, getWidth(), getHeight(), 3);
+
+        return true;
+    }
+
+    return false;
+}
+
 void LLImageRaw::expandToPowerOfTwo(S32 max_dim, bool scale_image)
 {
 	// Find new sizes
@@ -1110,7 +1139,7 @@ void LLImageRaw::composite( LLImageRaw* src )
 		return;
 	}
 
-	llassert(3 == src->getComponents());
+	llassert((3 == src->getComponents()) || (4 == src->getComponents()));
 	llassert(3 == dst->getComponents());
 
 	if( 3 == dst->getComponents() )
@@ -1268,6 +1297,30 @@ void LLImageRaw::fill( const LLColor4U& color )
 	}
 }
 
+void LLImageRaw::tint( const LLColor3& color )
+{
+	llassert( (3 == getComponents()) || (4 == getComponents()) );
+	if (isBufferInvalid())
+	{
+		LL_WARNS() << "Invalid image buffer" << LL_ENDL;
+		return;
+	}
+
+	S32 pixels = getWidth() * getHeight();
+    const S32 components = getComponents();
+    U8* data = getData();
+    for( S32 i = 0; i < pixels; i++ )
+    {
+        const float c0 = data[0] * color.mV[0];
+        const float c1 = data[1] * color.mV[1];
+        const float c2 = data[2] * color.mV[2];
+        data[0] = llclamp((U8)c0, 0, 255);
+        data[1] = llclamp((U8)c1, 0, 255);
+        data[2] = llclamp((U8)c2, 0, 255);
+        data += components;
+    }
+}
+
 LLPointer<LLImageRaw> LLImageRaw::duplicate()
 {
 	if(getNumRefs() < 2)
diff --git a/indra/llimage/llimage.h b/indra/llimage/llimage.h
index d1929b693f..fc8d62cc96 100644
--- a/indra/llimage/llimage.h
+++ b/indra/llimage/llimage.h
@@ -71,6 +71,7 @@ const S32 HTTP_PACKET_SIZE = 1496;
 class LLImageFormatted;
 class LLImageRaw;
 class LLColor4U;
+class LLColor3;
 
 typedef enum e_image_codec
 {
@@ -212,6 +213,8 @@ public:
     // if the alpha channel is all 100% opaque, delete it
     // returns true if alpha channel was deleted
     bool optimizeAwayAlpha();
+    // Create an alpha channel if this image doesn't have one
+    bool makeAlpha();
 
     static S32 biasedDimToPowerOfTwo(S32 curr_dim, S32 max_dim = MAX_IMAGE_SIZE);
     static S32 expandDimToPowerOfTwo(S32 curr_dim, S32 max_dim = MAX_IMAGE_SIZE);
@@ -225,6 +228,9 @@ public:
 	// Fill the buffer with a constant color
 	void fill( const LLColor4U& color );
 
+    // Multiply this raw image by the given color
+    void tint( const LLColor3& color );
+
 	// Copy operations
 	
 	//duplicate this raw image if refCount > 1.
diff --git a/indra/llmath/llvolume.cpp b/indra/llmath/llvolume.cpp
index 6d36daa92a..a5f047d207 100644
--- a/indra/llmath/llvolume.cpp
+++ b/indra/llmath/llvolume.cpp
@@ -6465,9 +6465,6 @@ BOOL LLVolumeFace::createCap(LLVolume* volume, BOOL partial_build)
 	return TRUE;
 }
 
-void CalculateTangentArray(U32 vertexCount, const LLVector4a *vertex, const LLVector4a *normal,
-        const LLVector2 *texcoord, U32 triangleCount, const U16* index_array, LLVector4a *tangent);
-
 void LLVolumeFace::createTangents()
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_VOLUME;
@@ -6485,7 +6482,7 @@ void LLVolumeFace::createTangents()
             (*ptr++).clear();
         }
 
-        CalculateTangentArray(mNumVertices, mPositions, mNormals, mTexCoords, mNumIndices / 3, mIndices, mTangents);
+        LLCalculateTangentArray(mNumVertices, mPositions, mNormals, mTexCoords, mNumIndices / 3, mIndices, mTangents);
 
         //normalize normals
         for (U32 i = 0; i < mNumVertices; i++)
@@ -7195,7 +7192,7 @@ BOOL LLVolumeFace::createSide(LLVolume* volume, BOOL partial_build)
 }
 
 //adapted from Lengyel, Eric. "Computing Tangent Space Basis Vectors for an Arbitrary Mesh". Terathon Software 3D Graphics Library, 2001. http://www.terathon.com/code/tangent.html
-void CalculateTangentArray(U32 vertexCount, const LLVector4a *vertex, const LLVector4a *normal,
+void LLCalculateTangentArray(U32 vertexCount, const LLVector4a *vertex, const LLVector4a *normal,
         const LLVector2 *texcoord, U32 triangleCount, const U16* index_array, LLVector4a *tangent)
 {
 	LL_PROFILE_ZONE_SCOPED_CATEGORY_VOLUME
diff --git a/indra/llmath/llvolume.h b/indra/llmath/llvolume.h
index afed98ff36..c2586601ae 100644
--- a/indra/llmath/llvolume.h
+++ b/indra/llmath/llvolume.h
@@ -1142,6 +1142,8 @@ public:
 
 std::ostream& operator<<(std::ostream &s, const LLVolumeParams &volume_params);
 
+void LLCalculateTangentArray(U32 vertexCount, const LLVector4a *vertex, const LLVector4a *normal, const LLVector2 *texcoord, U32 triangleCount, const U16* index_array, LLVector4a *tangent);
+
 BOOL LLLineSegmentBoxIntersect(const F32* start, const F32* end, const F32* center, const F32* size);
 BOOL LLLineSegmentBoxIntersect(const LLVector3& start, const LLVector3& end, const LLVector3& center, const LLVector3& size);
 BOOL LLLineSegmentBoxIntersect(const LLVector4a& start, const LLVector4a& end, const LLVector4a& center, const LLVector4a& size);
diff --git a/indra/llrender/llglslshader.h b/indra/llrender/llglslshader.h
index 43d095f73a..b18b56c59d 100644
--- a/indra/llrender/llglslshader.h
+++ b/indra/llrender/llglslshader.h
@@ -56,6 +56,7 @@ public:
     bool hasAlphaMask = false;
     bool hasReflectionProbes = false;
     bool attachNothing = false;
+    bool isPBRTerrain = false; // include: shaders\class1\deferred\pbrterrainUtilF.glsl
 };
 
 // ============= Structure for caching shader uniforms ===============
diff --git a/indra/llrender/llshadermgr.cpp b/indra/llrender/llshadermgr.cpp
index f78be910d2..5522c8f9ad 100644
--- a/indra/llrender/llshadermgr.cpp
+++ b/indra/llrender/llshadermgr.cpp
@@ -277,6 +277,14 @@ BOOL LLShaderMgr::attachShaderFeatures(LLGLSLShader * shader)
 		}
 	}
 	
+    if (features->isPBRTerrain)
+    {
+        if (!shader->attachFragmentObject("deferred/pbrterrainUtilF.glsl"))
+        {
+            return FALSE;
+        }
+    }
+	
 	// NOTE order of shader object attaching is VERY IMPORTANT!!!
 	if (features->hasAtmospherics)
 	{
@@ -1374,8 +1382,32 @@ void LLShaderMgr::initAttribsAndUniforms()
 	mReservedUniforms.push_back("detail_1");
 	mReservedUniforms.push_back("detail_2");
 	mReservedUniforms.push_back("detail_3");
+
 	mReservedUniforms.push_back("alpha_ramp");
 
+	mReservedUniforms.push_back("detail_0_base_color");
+	mReservedUniforms.push_back("detail_1_base_color");
+	mReservedUniforms.push_back("detail_2_base_color");
+	mReservedUniforms.push_back("detail_3_base_color");
+	mReservedUniforms.push_back("detail_0_normal");
+	mReservedUniforms.push_back("detail_1_normal");
+	mReservedUniforms.push_back("detail_2_normal");
+	mReservedUniforms.push_back("detail_3_normal");
+	mReservedUniforms.push_back("detail_0_metallic_roughness");
+	mReservedUniforms.push_back("detail_1_metallic_roughness");
+	mReservedUniforms.push_back("detail_2_metallic_roughness");
+	mReservedUniforms.push_back("detail_3_metallic_roughness");
+	mReservedUniforms.push_back("detail_0_emissive");
+	mReservedUniforms.push_back("detail_1_emissive");
+	mReservedUniforms.push_back("detail_2_emissive");
+	mReservedUniforms.push_back("detail_3_emissive");
+
+    mReservedUniforms.push_back("baseColorFactors");
+    mReservedUniforms.push_back("metallicFactors");
+    mReservedUniforms.push_back("roughnessFactors");
+    mReservedUniforms.push_back("emissiveColors");
+    mReservedUniforms.push_back("minimum_alphas");
+
 	mReservedUniforms.push_back("origin");
 	mReservedUniforms.push_back("display_gamma");
 
diff --git a/indra/llrender/llshadermgr.h b/indra/llrender/llshadermgr.h
index 79a24773e1..5c99a6b42d 100644
--- a/indra/llrender/llshadermgr.h
+++ b/indra/llrender/llshadermgr.h
@@ -251,8 +251,32 @@ public:
         TERRAIN_DETAIL1,                    //  "detail_1"
         TERRAIN_DETAIL2,                    //  "detail_2"
         TERRAIN_DETAIL3,                    //  "detail_3"
+
         TERRAIN_ALPHARAMP,                  //  "alpha_ramp"
 
+        TERRAIN_DETAIL0_BASE_COLOR,                //  "detail_0_base_color" (GLTF)
+        TERRAIN_DETAIL1_BASE_COLOR,                //  "detail_1_base_color" (GLTF)
+        TERRAIN_DETAIL2_BASE_COLOR,                //  "detail_2_base_color" (GLTF)
+        TERRAIN_DETAIL3_BASE_COLOR,                //  "detail_3_base_color" (GLTF)
+        TERRAIN_DETAIL0_NORMAL,                    //  "detail_0_normal" (GLTF)
+        TERRAIN_DETAIL1_NORMAL,                    //  "detail_1_normal" (GLTF)
+        TERRAIN_DETAIL2_NORMAL,                    //  "detail_2_normal" (GLTF)
+        TERRAIN_DETAIL3_NORMAL,                    //  "detail_3_normal" (GLTF)
+        TERRAIN_DETAIL0_METALLIC_ROUGHNESS,        //  "detail_0_metallic_roughness" (GLTF)
+        TERRAIN_DETAIL1_METALLIC_ROUGHNESS,        //  "detail_1_metallic_roughness" (GLTF)
+        TERRAIN_DETAIL2_METALLIC_ROUGHNESS,        //  "detail_2_metallic_roughness" (GLTF)
+        TERRAIN_DETAIL3_METALLIC_ROUGHNESS,        //  "detail_3_metallic_roughness" (GLTF)
+        TERRAIN_DETAIL0_EMISSIVE,                  //  "detail_0_emissive" (GLTF)
+        TERRAIN_DETAIL1_EMISSIVE,                  //  "detail_1_emissive" (GLTF)
+        TERRAIN_DETAIL2_EMISSIVE,                  //  "detail_2_emissive" (GLTF)
+        TERRAIN_DETAIL3_EMISSIVE,                  //  "detail_3_emissive" (GLTF)
+
+        TERRAIN_BASE_COLOR_FACTORS,                //  "baseColorFactors" (GLTF)
+        TERRAIN_METALLIC_FACTORS,                  //  "metallicFactors" (GLTF)
+        TERRAIN_ROUGHNESS_FACTORS,                 //  "roughnessFactors" (GLTF)
+        TERRAIN_EMISSIVE_COLORS,                   //  "emissiveColors" (GLTF)
+        TERRAIN_MINIMUM_ALPHAS,                    //  "minimum_alphas" (GLTF)
+
         SHINY_ORIGIN,                       //  "origin"
         DISPLAY_GAMMA,                      //  "display_gamma"
 
diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 4a95cb1ed2..df30b8d298 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -10825,7 +10825,7 @@
     <key>RenderTerrainScale</key>
     <map>
       <key>Comment</key>
-      <string>Terrain detail texture scale</string>
+      <string>Terrain detail texture scale (meters)</string>
       <key>Persist</key>
       <integer>1</integer>
       <key>Type</key>
@@ -10833,6 +10833,61 @@
       <key>Value</key>
       <real>12.0</real>
     </map>
+    <key>RenderTerrainPBREnabled</key>
+    <map>
+      <key>Comment</key>
+      <string>EXPERIMENTAL: Enable PBR Terrain features. Requires restart.</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>Boolean</string>
+      <key>Value</key>
+      <integer>0</integer>
+    </map>
+    <key>RenderTerrainPBRDetail</key>
+    <map>
+      <key>Comment</key>
+      <string>Detail level for PBR terrain. 0 is full detail. Negative values drop rendering features in accordance with the GLTF specification, which reduces the number of texture binds. Some Intel and Mac graphics drivers do not support more than 16 texture binds. Because PBR terrain exceeds this limit at the highest detail level, reducing texture binds is necessary for compatibility.</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>S32</string>
+      <key>Value</key>
+      <integer>0</integer>
+    </map>
+    <key>RenderTerrainPBRScale</key>
+    <map>
+      <key>Comment</key>
+      <string>PBR terrain detail texture scale (meters)</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>F32</string>
+      <key>Value</key>
+      <real>4.0</real>
+    </map>
+    <key>RenderTerrainPBRPlanarSampleCount</key>
+    <map>
+      <key>Comment</key>
+      <string>How many UV planes to sample PBR terrain textures from. 1 is "flat", 3 is triplanar mapping (aka box mapping)</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>S32</string>
+      <key>Value</key>
+      <real>3</real>
+    </map>
+    <key>RenderTerrainPBRTriplanarBlendFactor</key>
+    <map>
+      <key>Comment</key>
+      <string>Higher values create sharper transitions, but are more likely to produce artifacts.</string>
+      <key>Persist</key>
+      <integer>1</integer>
+      <key>Type</key>
+      <string>F32</string>
+      <key>Value</key>
+      <real>8.0</real>
+    </map>
     <key>RenderTrackerBeacon</key>
     <map>
       <key>Comment</key>
@@ -16576,6 +16631,50 @@
       <key>Value</key>
       <integer>0</integer>
     </map>
+	<key>LocalTerrainAsset1</key>
+    <map>
+      <key>Comment</key>
+      <string>If set to a non-null UUID, overrides the terrain asset locally for all regions with material assets. Local terrain assets are not visible to others. Please keep in mind that this debug setting may be temporary. Do not rely on this setting existing in future viewer builds.</string>
+      <key>Persist</key>
+      <integer>0</integer>
+      <key>Type</key>
+      <string>String</string>
+      <key>Value</key>
+      <string>00000000-0000-0000-0000-000000000000</string>
+    </map>
+	<key>LocalTerrainAsset2</key>
+    <map>
+      <key>Comment</key>
+      <string>If set to a non-null UUID, overrides the terrain asset locally for all regions with material assets. Local terrain assets are not visible to others. Please keep in mind that this debug setting may be temporary. Do not rely on this setting existing in future viewer builds.</string>
+      <key>Persist</key>
+      <integer>0</integer>
+      <key>Type</key>
+      <string>String</string>
+      <key>Value</key>
+      <string>00000000-0000-0000-0000-000000000000</string>
+    </map>
+	<key>LocalTerrainAsset3</key>
+    <map>
+      <key>Comment</key>
+      <string>If set to a non-null UUID, overrides the terrain asset locally for all regions with material assets. Local terrain assets are not visible to others. Please keep in mind that this debug setting may be temporary. Do not rely on this setting existing in future viewer builds.</string>
+      <key>Persist</key>
+      <integer>0</integer>
+      <key>Type</key>
+      <string>String</string>
+      <key>Value</key>
+      <string>00000000-0000-0000-0000-000000000000</string>
+    </map>
+	<key>LocalTerrainAsset4</key>
+    <map>
+      <key>Comment</key>
+      <string>If set to a non-null UUID, overrides the terrain asset locally for all regions with material assets. Local terrain assets are not visible to others. Please keep in mind that this debug setting may be temporary. Do not rely on this setting existing in future viewer builds.</string>
+      <key>Persist</key>
+      <integer>0</integer>
+      <key>Type</key>
+      <string>String</string>
+      <key>Value</key>
+      <string>00000000-0000-0000-0000-000000000000</string>
+    </map>
 	<key>PathfindingRetrieveNeighboringRegion</key>
     <map>
       <key>Comment</key>
diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbrterrainF.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainF.glsl
new file mode 100644
index 0000000000..db03e0885c
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainF.glsl
@@ -0,0 +1,272 @@
+/** 
+ * @file class1\deferred\terrainF.glsl
+ *
+ * $LicenseInfo:firstyear=2023&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2023, Linden Research, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+/*[EXTRA_CODE_HERE]*/
+
+#define TERRAIN_PBR_DETAIL_EMISSIVE 0
+
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+#define TerrainCoord vec4[2]
+#elif TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 1
+#define TerrainCoord vec2
+#endif
+
+#define MIX_X    1 << 3
+#define MIX_Y    1 << 4
+#define MIX_Z    1 << 5
+#define MIX_W    1 << 6
+
+// TODO: Decide if this struct needs to be declared
+struct TerrainMix
+{
+    vec4 weight;
+    int type;
+};
+
+TerrainMix get_terrain_mix_weights(float alpha1, float alpha2, float alphaFinal);
+
+// TODO: Decide if this struct needs to be declared
+struct PBRMix
+{
+    vec4 col;       // RGB color with alpha, linear space
+    vec3 orm;       // Occlusion, roughness, metallic
+    vec3 vNt;       // Unpacked normal texture sample, vector
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    vec3 emissive;  // RGB emissive color, linear space
+#endif
+};
+
+PBRMix init_pbr_mix();
+
+PBRMix terrain_sample_and_multiply_pbr(
+    TerrainCoord terrain_coord
+    , sampler2D tex_col
+    , sampler2D tex_orm
+    , sampler2D tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , sampler2D tex_emissive
+#endif
+    , vec4 factor_col
+    , vec3 factor_orm
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , vec3 factor_emissive
+#endif
+    );
+
+PBRMix mix_pbr(PBRMix mix1, PBRMix mix2, float mix2_weight);
+
+out vec4 frag_data[4];
+
+uniform sampler2D alpha_ramp;
+
+// *TODO: More configurable quality level which disables PBR features on machines
+// with limited texture availability
+// https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#additional-textures
+uniform sampler2D detail_0_base_color;
+uniform sampler2D detail_1_base_color;
+uniform sampler2D detail_2_base_color;
+uniform sampler2D detail_3_base_color;
+uniform sampler2D detail_0_normal;
+uniform sampler2D detail_1_normal;
+uniform sampler2D detail_2_normal;
+uniform sampler2D detail_3_normal;
+uniform sampler2D detail_0_metallic_roughness;
+uniform sampler2D detail_1_metallic_roughness;
+uniform sampler2D detail_2_metallic_roughness;
+uniform sampler2D detail_3_metallic_roughness;
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+uniform sampler2D detail_0_emissive;
+uniform sampler2D detail_1_emissive;
+uniform sampler2D detail_2_emissive;
+uniform sampler2D detail_3_emissive;
+#endif
+
+uniform vec4[4] baseColorFactors; // See also vertex_color in pbropaqueV.glsl
+uniform vec4 metallicFactors;
+uniform vec4 roughnessFactors;
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+uniform vec3[4] emissiveColors;
+#endif
+uniform vec4 minimum_alphas; // PBR alphaMode: MASK, See: mAlphaCutoff, setAlphaCutoff()
+
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+in vec4[2] vary_coords;
+#endif
+in vec3 vary_normal;
+in vec3 vary_tangent;
+flat in float vary_sign;
+in vec4 vary_texcoord0;
+in vec4 vary_texcoord1;
+
+vec2 encode_normal(vec3 n);
+
+float terrain_mix(TerrainMix tm, vec4 tms4);
+
+void main()
+{
+
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+    TerrainCoord terrain_texcoord = vary_coords;
+#elif TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 1
+    TerrainCoord terrain_texcoord = vary_texcoord0.xy;
+#endif
+
+    float alpha1 = texture(alpha_ramp, vary_texcoord0.zw).a;
+    float alpha2 = texture(alpha_ramp,vary_texcoord1.xy).a;
+    float alphaFinal = texture(alpha_ramp, vary_texcoord1.zw).a;
+
+    TerrainMix tm = get_terrain_mix_weights(alpha1, alpha2, alphaFinal);
+
+    // RGB = Occlusion, Roughness, Metal
+    // default values, see LLViewerTexture::sDefaultPBRORMImagep
+    //   occlusion 1.0
+    //   roughness 0.0
+    //   metal     0.0
+    vec3[4] orm_factors;
+    orm_factors[0] = vec3(1.0, roughnessFactors.x, metallicFactors.x);
+    orm_factors[1] = vec3(1.0, roughnessFactors.y, metallicFactors.y);
+    orm_factors[2] = vec3(1.0, roughnessFactors.z, metallicFactors.z);
+    orm_factors[3] = vec3(1.0, roughnessFactors.w, metallicFactors.w);
+
+    PBRMix mix = init_pbr_mix();
+    PBRMix mix2;
+    switch (tm.type & MIX_X)
+    {
+    case MIX_X:
+        mix2 = terrain_sample_and_multiply_pbr(
+            terrain_texcoord
+            , detail_0_base_color
+            , detail_0_metallic_roughness
+            , detail_0_normal
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , detail_0_emissive
+#endif
+            , baseColorFactors[0]
+            , orm_factors[0]
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , emissiveColors[0]
+#endif
+        );
+        mix = mix_pbr(mix, mix2, tm.weight.x);
+        break;
+    default:
+        break;
+    }
+    switch (tm.type & MIX_Y)
+    {
+    case MIX_Y:
+        mix2 = terrain_sample_and_multiply_pbr(
+            terrain_texcoord
+            , detail_1_base_color
+            , detail_1_metallic_roughness
+            , detail_1_normal
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , detail_1_emissive
+#endif
+            , baseColorFactors[1]
+            , orm_factors[1]
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , emissiveColors[1]
+#endif
+        );
+        mix = mix_pbr(mix, mix2, tm.weight.y);
+        break;
+    default:
+        break;
+    }
+    switch (tm.type & MIX_Z)
+    {
+    case MIX_Z:
+        mix2 = terrain_sample_and_multiply_pbr(
+            terrain_texcoord
+            , detail_2_base_color
+            , detail_2_metallic_roughness
+            , detail_2_normal
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , detail_2_emissive
+#endif
+            , baseColorFactors[2]
+            , orm_factors[2]
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , emissiveColors[2]
+#endif
+        );
+        mix = mix_pbr(mix, mix2, tm.weight.z);
+        break;
+    default:
+        break;
+    }
+    switch (tm.type & MIX_W)
+    {
+    case MIX_W:
+        mix2 = terrain_sample_and_multiply_pbr(
+            terrain_texcoord
+            , detail_3_base_color
+            , detail_3_metallic_roughness
+            , detail_3_normal
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , detail_3_emissive
+#endif
+            , baseColorFactors[3]
+            , orm_factors[3]
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , emissiveColors[3]
+#endif
+        );
+        mix = mix_pbr(mix, mix2, tm.weight.w);
+        break;
+    default:
+        break;
+    }
+
+    float minimum_alpha = terrain_mix(tm, minimum_alphas);
+    if (mix.col.a < minimum_alpha)
+    {
+        discard;
+    }
+    float base_color_factor_alpha = terrain_mix(tm, vec4(baseColorFactors[0].z, baseColorFactors[1].z, baseColorFactors[2].z, baseColorFactors[3].z));
+
+    // from mikktspace.com
+    vec3 vNt = mix.vNt;
+    vec3 vN = vary_normal;
+    vec3 vT = vary_tangent.xyz;
+    
+    vec3 vB = vary_sign * cross(vN, vT);
+    vec3 tnorm = normalize( vNt.x * vT + vNt.y * vB + vNt.z * vN );
+
+    tnorm *= gl_FrontFacing ? 1.0 : -1.0;
+   
+
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+#define emissive mix.emissive
+#else
+#define emissive vec3(0)
+#endif
+    frag_data[0] = max(vec4(mix.col.xyz, 0.0), vec4(0));                                                   // Diffuse
+    frag_data[1] = max(vec4(mix.orm.rgb, base_color_factor_alpha), vec4(0));                                    // PBR linear packed Occlusion, Roughness, Metal.
+    frag_data[2] = max(vec4(encode_normal(tnorm), base_color_factor_alpha, GBUFFER_FLAG_HAS_PBR), vec4(0)); // normal, environment intensity, flags
+    frag_data[3] = max(vec4(emissive,0), vec4(0));                                                // PBR sRGB Emissive
+}
+
diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl
new file mode 100644
index 0000000000..316b751590
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainUtilF.glsl
@@ -0,0 +1,396 @@
+/** 
+ * @file class1\deferred\pbrterrainUtilF.glsl
+ *
+ * $LicenseInfo:firstyear=2023&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2023, Linden Research, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+/*[EXTRA_CODE_HERE]*/
+
+/**
+ * Triplanar mapping implementation adapted from Inigo Quilez' example shader,
+ * MIT license.
+ * https://www.shadertoy.com/view/MtsGWH
+ * Copyright © 2015 Inigo Quilez
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions: The above copyright
+ * notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS",
+ * WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+ * TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+ * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#define TERRAIN_PBR_DETAIL_EMISSIVE 0
+
+in vec3 vary_vertex_normal;
+
+vec3 srgb_to_linear(vec3 c);
+
+// A relatively agressive threshold for terrain material mixing sampling
+// cutoff. This ensures that only one or two materials are used in most places,
+// making PBR terrain blending more performant. Should be greater than 0 to work.
+#define TERRAIN_RAMP_MIX_THRESHOLD 0.1
+// A small threshold for triplanar mapping sampling cutoff. This and
+// TERRAIN_TRIPLANAR_BLEND_FACTOR together ensures that only one or two samples
+// per texture are used in most places, making triplanar mapping more
+// performant. Should be greater than 0 to work.
+// There's also an artistic design choice in the use of these factors, and the
+// use of triplanar generally. Don't take these triplanar constants for granted.
+#define TERRAIN_TRIPLANAR_MIX_THRESHOLD 0.01
+
+#define SAMPLE_X 1 << 0
+#define SAMPLE_Y 1 << 1
+#define SAMPLE_Z 1 << 2
+#define MIX_X    1 << 3
+#define MIX_Y    1 << 4
+#define MIX_Z    1 << 5
+#define MIX_W    1 << 6
+
+struct PBRMix
+{
+    vec4 col;       // RGB color with alpha, linear space
+    vec3 orm;       // Occlusion, roughness, metallic
+    vec3 vNt;       // Unpacked normal texture sample, vector
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    vec3 emissive;  // RGB emissive color, linear space
+#endif
+};
+
+PBRMix init_pbr_mix()
+{
+    PBRMix mix;
+    mix.col = vec4(0);
+    mix.orm = vec3(0);
+    mix.vNt = vec3(0);
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    mix.emissive = vec3(0);
+#endif
+    return mix;
+}
+
+// Usage example, for two weights:
+// vec2 weights = ... // Weights must add up to 1
+// PBRMix mix = init_pbr_mix();
+// PBRMix mix1 = ...
+// mix = mix_pbr(mix, mix1, weights.x);
+// PBRMix mix2 = ...
+// mix = mix_pbr(mix, mix2, weights.y);
+PBRMix mix_pbr(PBRMix mix1, PBRMix mix2, float mix2_weight)
+{
+    PBRMix mix;
+    mix.col      = mix1.col      + (mix2.col      * mix2_weight);
+    mix.orm      = mix1.orm      + (mix2.orm      * mix2_weight);
+    mix.vNt      = mix1.vNt      + (mix2.vNt      * mix2_weight);
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    mix.emissive = mix1.emissive + (mix2.emissive * mix2_weight);
+#endif
+    return mix;
+}
+
+PBRMix sample_pbr(
+    vec2 uv
+    , sampler2D tex_col
+    , sampler2D tex_orm
+    , sampler2D tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , sampler2D tex_emissive
+#endif
+    )
+{
+    PBRMix mix;
+    mix.col = texture(tex_col, uv);
+    mix.col.rgb = srgb_to_linear(mix.col.rgb);
+    mix.orm = texture(tex_orm, uv).xyz;
+    mix.vNt = texture(tex_vNt, uv).xyz*2.0-1.0;
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    mix.emissive = srgb_to_linear(texture(tex_emissive, uv).xyz);
+#endif
+    return mix;
+}
+
+struct TerrainTriplanar
+{
+    vec3 weight;
+    int type;
+};
+
+struct TerrainMix
+{
+    vec4 weight;
+    int type;
+};
+
+#define TerrainMixSample vec4[4]
+#define TerrainMixSample3 vec3[4]
+
+TerrainMix get_terrain_mix_weights(float alpha1, float alpha2, float alphaFinal)
+{
+    TerrainMix tm;
+    vec4 sample_x = vec4(1,0,0,0);
+    vec4 sample_y = vec4(0,1,0,0);
+    vec4 sample_z = vec4(0,0,1,0);
+    vec4 sample_w = vec4(0,0,0,1);
+
+    tm.weight = mix( mix(sample_w, sample_z, alpha2), mix(sample_y, sample_x, alpha1), alphaFinal );
+    tm.weight -= TERRAIN_RAMP_MIX_THRESHOLD;
+    ivec4 usage = max(ivec4(0), ivec4(ceil(tm.weight)));
+    // Prevent negative weights and keep weights balanced
+    tm.weight = tm.weight*vec4(usage);
+    tm.weight /= (tm.weight.x + tm.weight.y + tm.weight.z + tm.weight.w);
+
+    tm.type = (usage.x * MIX_X) |
+              (usage.y * MIX_Y) |
+              (usage.z * MIX_Z) |
+              (usage.w * MIX_W);
+    return tm;
+}
+
+TerrainTriplanar _t_triplanar()
+{
+    float sharpness = TERRAIN_TRIPLANAR_BLEND_FACTOR;
+    float threshold = TERRAIN_TRIPLANAR_MIX_THRESHOLD;
+    vec3 weight_signed = pow(abs(vary_vertex_normal), vec3(sharpness));
+    weight_signed /= (weight_signed.x + weight_signed.y + weight_signed.z);
+    weight_signed -= vec3(threshold);
+    TerrainTriplanar tw;
+    // *NOTE: Make sure the threshold doesn't affect the materials
+    tw.weight = max(vec3(0), weight_signed);
+    tw.weight /= (tw.weight.x + tw.weight.y + tw.weight.z);
+    ivec3 usage = ivec3(round(max(vec3(0), sign(weight_signed))));
+    tw.type = ((usage.x) * SAMPLE_X) |
+              ((usage.y) * SAMPLE_Y) |
+              ((usage.z) * SAMPLE_Z);
+    return tw;
+}
+
+// Assume weights add to 1
+float terrain_mix(TerrainMix tm, vec4 tms4)
+{
+    return (tm.weight.x * tms4[0]) +
+           (tm.weight.y * tms4[1]) +
+           (tm.weight.z * tms4[2]) +
+           (tm.weight.w * tms4[3]);
+}
+
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+// Triplanar mapping
+
+// Pre-transformed texture coordinates for each axial uv slice (Packing: xy, yz, (-x)z, unused)
+#define TerrainCoord vec4[2]
+
+vec2 _t_uv(vec2 uv_unflipped, float sign_or_zero)
+{
+    // Handle case where sign is 0
+    float sign = (2.0*sign_or_zero) + 1.0;
+    sign /= abs(sign);
+    // If the vertex normal is negative, flip the texture back
+    // right-side up.
+    vec2 uv = uv_unflipped * vec2(sign, 1);
+    return uv;
+}
+
+vec3 _t_normal_post_1(vec3 vNt0, float sign_or_zero)
+{
+    // Assume normal is unpacked
+    vec3 vNt1 = vNt0;
+    // Get sign
+    float sign = sign_or_zero;
+    // Handle case where sign is 0
+    sign = (2.0*sign) + 1.0;
+    sign /= abs(sign);
+    // If the sign is negative, rotate normal by 180 degrees
+    vNt1.xy = (min(0, sign) * vNt1.xy) + (min(0, -sign) * -vNt1.xy);
+    return vNt1;
+}
+
+// Triplanar-specific normal texture fixes
+vec3 _t_normal_post_x(vec3 vNt0)
+{
+    vec3 vNt_x = _t_normal_post_1(vNt0, sign(vary_vertex_normal.x));
+    // *HACK: Transform normals according to orientation of the UVs
+    vNt_x.xy = vec2(-vNt_x.y, vNt_x.x);
+    return vNt_x;
+}
+vec3 _t_normal_post_y(vec3 vNt0)
+{
+    vec3 vNt_y = _t_normal_post_1(vNt0, sign(vary_vertex_normal.y));
+    // *HACK: Transform normals according to orientation of the UVs
+    vNt_y.xy = -vNt_y.xy;
+    return vNt_y;
+}
+vec3 _t_normal_post_z(vec3 vNt0)
+{
+    vec3 vNt_z = _t_normal_post_1(vNt0, sign(vary_vertex_normal.z));
+    return vNt_z;
+}
+
+PBRMix terrain_sample_pbr(
+    TerrainCoord terrain_coord
+    , TerrainTriplanar tw
+    , sampler2D tex_col
+    , sampler2D tex_orm
+    , sampler2D tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , sampler2D tex_emissive
+#endif
+    )
+{
+    PBRMix mix = init_pbr_mix();
+
+#define get_uv_x() _t_uv(terrain_coord[0].zw, sign(vary_vertex_normal.x))
+#define get_uv_y() _t_uv(terrain_coord[1].xy, sign(vary_vertex_normal.y))
+#define get_uv_z() _t_uv(terrain_coord[0].xy, sign(vary_vertex_normal.z))
+    switch (tw.type & SAMPLE_X)
+    {
+    case SAMPLE_X:
+        PBRMix mix_x = sample_pbr(
+            get_uv_x()
+            , tex_col
+            , tex_orm
+            , tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , tex_emissive
+#endif
+            );
+        // Triplanar-specific normal texture fix
+        mix_x.vNt = _t_normal_post_x(mix_x.vNt);
+        mix = mix_pbr(mix, mix_x, tw.weight.x);
+        break;
+    default:
+        break;
+    }
+
+    switch (tw.type & SAMPLE_Y)
+    {
+    case SAMPLE_Y:
+        PBRMix mix_y = sample_pbr(
+            get_uv_y()
+            , tex_col
+            , tex_orm
+            , tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , tex_emissive
+#endif
+            );
+        // Triplanar-specific normal texture fix
+        mix_y.vNt = _t_normal_post_y(mix_y.vNt);
+        mix = mix_pbr(mix, mix_y, tw.weight.y);
+        break;
+    default:
+        break;
+    }
+
+    switch (tw.type & SAMPLE_Z)
+    {
+    case SAMPLE_Z:
+        PBRMix mix_z = sample_pbr(
+            get_uv_z()
+            , tex_col
+            , tex_orm
+            , tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+            , tex_emissive
+#endif
+            );
+        // Triplanar-specific normal texture fix
+        // *NOTE: Bottom face has not been tested
+        mix_z.vNt = _t_normal_post_z(mix_z.vNt);
+        mix = mix_pbr(mix, mix_z, tw.weight.z);
+        break;
+    default:
+        break;
+    }
+    
+    return mix;
+}
+
+#elif TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 1
+
+#define TerrainCoord vec2
+
+#define terrain_sample_pbr sample_pbr
+
+#endif
+
+PBRMix multiply_factors_pbr(
+    PBRMix mix_in
+    , vec4 factor_col
+    , vec3 factor_orm
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , vec3 factor_emissive
+#endif
+    )
+{
+    PBRMix mix = mix_in;
+    mix.col *= factor_col;
+    mix.orm *= factor_orm;
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    mix.emissive *= factor_emissive;
+#endif
+    return mix;
+}
+
+PBRMix terrain_sample_and_multiply_pbr(
+    TerrainCoord terrain_coord
+    , sampler2D tex_col
+    , sampler2D tex_orm
+    , sampler2D tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , sampler2D tex_emissive
+#endif
+    , vec4 factor_col
+    , vec3 factor_orm
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+    , vec3 factor_emissive
+#endif
+    )
+{
+    PBRMix mix = terrain_sample_pbr(
+        terrain_coord
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+        , _t_triplanar()
+#endif
+        , tex_col
+        , tex_orm
+        , tex_vNt
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+        , tex_emissive
+#endif
+        );
+
+    mix = multiply_factors_pbr(mix
+        , factor_col
+        , factor_orm
+#if (TERRAIN_PBR_DETAIL >= TERRAIN_PBR_DETAIL_EMISSIVE)
+        , factor_emissive
+#endif
+    );
+
+    return mix;
+}
diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbrterrainV.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainV.glsl
new file mode 100644
index 0000000000..dbb9404219
--- /dev/null
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbrterrainV.glsl
@@ -0,0 +1,93 @@
+/** 
+ * @file class1\environment\pbrterrainV.glsl
+ *
+ * $LicenseInfo:firstyear=2023&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2023, Linden Research, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+
+uniform mat3 normal_matrix;
+uniform mat4 texture_matrix0;
+uniform mat4 modelview_projection_matrix;
+
+in vec3 position;
+in vec3 normal;
+in vec4 tangent;
+in vec4 diffuse_color;
+in vec2 texcoord1;
+
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+out vec4[2] vary_coords;
+#endif
+out vec3 vary_vertex_normal; // Used by pbrterrainUtilF.glsl
+out vec3 vary_normal;
+out vec3 vary_tangent;
+flat out float vary_sign;
+out vec4 vary_texcoord0;
+out vec4 vary_texcoord1;
+
+// *HACK: tangent_space_transform should use texture_normal_transform, or maybe
+// we shouldn't use tangent_space_transform at all. See the call to
+// tangent_space_transform below.
+uniform vec4[2] texture_base_color_transform;
+
+vec2 texture_transform(vec2 vertex_texcoord, vec4[2] khr_gltf_transform, mat4 sl_animation_transform);
+vec3 tangent_space_transform(vec4 vertex_tangent, vec3 vertex_normal, vec4[2] khr_gltf_transform, mat4 sl_animation_transform);
+
+void main()
+{
+    //transform vertex
+	gl_Position = modelview_projection_matrix * vec4(position.xyz, 1.0); 
+
+	vec3 n = normal_matrix * normal;
+    vary_vertex_normal = normal;
+	vec3 t = normal_matrix * tangent.xyz;
+
+    vary_tangent = normalize(t);
+    // *TODO: Decide if we want this. It may be better to just calculate the
+    // tangents on-the-fly in the fragment shader, due to the subtleties of the
+    // effect of triplanar mapping on UVs.
+    // *HACK: Should be using texture_normal_transform here. The KHR texture
+    // transform spec requires handling texture transforms separately for each
+    // individual texture.
+    vary_tangent = normalize(tangent_space_transform(vec4(t, tangent.w), n, texture_base_color_transform, texture_matrix0));
+    vary_sign = tangent.w;
+    vary_normal = normalize(n);
+
+    // Transform and pass tex coords
+    // *HACK: texture_base_color_transform is used for all of these here, but
+    // the KHR texture transform spec requires handling texture transforms
+    // separately for each individual texture.
+#if TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 3
+    // xy
+    vary_coords[0].xy = texture_transform(position.xy, texture_base_color_transform, texture_matrix0);
+    // yz
+    vary_coords[0].zw = texture_transform(position.yz, texture_base_color_transform, texture_matrix0);
+    // (-x)z
+    vary_coords[1].xy = texture_transform(position.xz * vec2(-1, 1), texture_base_color_transform, texture_matrix0);
+#elif TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT == 1
+    vary_texcoord0.xy = texture_transform(position.xy, texture_base_color_transform, texture_matrix0);
+#endif
+    
+    vec4 tc = vec4(texcoord1,0,1);
+    vary_texcoord0.zw = tc.xy;
+    vary_texcoord1.xy = tc.xy-vec2(2.0, 0.0);
+    vary_texcoord1.zw = tc.xy-vec2(1.0, 0.0);
+}
diff --git a/indra/newview/app_settings/shaders/class1/deferred/terrainV.glsl b/indra/newview/app_settings/shaders/class1/deferred/terrainV.glsl
index f6d3b59e85..33a78fd26d 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/terrainV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/terrainV.glsl
@@ -30,7 +30,6 @@ uniform mat4 modelview_projection_matrix;
 in vec3 position;
 in vec3 normal;
 in vec4 diffuse_color;
-in vec2 texcoord0;
 in vec2 texcoord1;
 
 out vec3 pos;
@@ -41,18 +40,16 @@ out vec4 vary_texcoord1;
 uniform vec4 object_plane_s;
 uniform vec4 object_plane_t;
 
-vec4 texgen_object(vec4  vpos, vec4 tc, mat4 mat, vec4 tp0, vec4 tp1)
+vec2 texgen_object(vec4 vpos, mat4 mat, vec4 tp0, vec4 tp1)
 {
     vec4 tcoord;
     
     tcoord.x = dot(vpos, tp0);
     tcoord.y = dot(vpos, tp1);
-    tcoord.z = tc.z;
-    tcoord.w = tc.w;
     
     tcoord = mat * tcoord; 
     
-    return tcoord; 
+    return tcoord.xy; 
 }
 
 void main()
@@ -67,7 +64,7 @@ void main()
     vary_normal = normalize(normal_matrix * normal);
     
     // Transform and pass tex coords
-    vary_texcoord0.xy = texgen_object(vec4(position, 1.0), vec4(texcoord0,0,1), texture_matrix0, object_plane_s, object_plane_t).xy;
+    vary_texcoord0.xy = texgen_object(vec4(position, 1.0), texture_matrix0, object_plane_s, object_plane_t);
     
     vec4 t = vec4(texcoord1,0,1);
     
diff --git a/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl b/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
index 636dfed4ba..732333311c 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
@@ -65,7 +65,7 @@ vec2 texture_transform(vec2 vertex_texcoord, vec4[2] khr_gltf_transform, mat4 sl
     // Apply texture animation first to avoid shearing and other artifacts
     texcoord = (sl_animation_transform * vec4(texcoord, 0, 1)).xy;
     // Convert to left-handed coordinate system. The offset of 1 is necessary
-    // for rotations to be applied correctly.
+    // for rotation and scale to be applied correctly.
     texcoord.y = 1.0 - texcoord.y;
     texcoord = khr_texture_transform(texcoord, khr_gltf_transform[0].xy, khr_gltf_transform[0].z, khr_gltf_transform[1].xy);
     // Convert back to right-handed coordinate system
diff --git a/indra/newview/featuretable.txt b/indra/newview/featuretable.txt
index f92d9a2a0e..c341097dfc 100644
--- a/indra/newview/featuretable.txt
+++ b/indra/newview/featuretable.txt
@@ -48,6 +48,8 @@ RenderReflectionsEnabled    1   1
 RenderReflectionProbeDetail	1	2
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRDetail      1   0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTreeLODFactor			1	1.0
 RenderVBOEnable				1	1
 RenderVBOMappingDisable		1	1
@@ -94,6 +96,7 @@ RenderReflectionsEnabled    1   1
 RenderReflectionProbeDetail	1	0
 RenderTerrainDetail			1	0
 RenderTerrainLODFactor		1	1
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTreeLODFactor			1	0
 RenderVolumeLODFactor		1	1.125
 RenderDeferredSSAO			1	0
@@ -123,6 +126,7 @@ RenderReflectionsEnabled    1   1
 RenderReflectionProbeDetail	1	0
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	1.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.125
 RenderDeferredSSAO			1	0
@@ -150,6 +154,7 @@ RenderLocalLightCount		1	512
 RenderTransparentWater      1   0
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.25
 RenderDeferredSSAO			1	0
@@ -179,6 +184,7 @@ RenderLocalLightCount		1	1024
 RenderTransparentWater      1   1
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.375
 RenderDeferredSSAO			1	0
@@ -208,6 +214,7 @@ RenderLocalLightCount		1	2048
 RenderTransparentWater      1   1
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.5
 RenderDeferredSSAO			1	1
@@ -236,6 +243,7 @@ RenderMaxPartCount			1	4096
 RenderLocalLightCount		1	4096
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.75
@@ -264,6 +272,7 @@ RenderLocalLightCount		1	8192
 RenderMaxPartCount			1	8192
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	1.0
 RenderVolumeLODFactor		1	2.0
@@ -321,3 +330,5 @@ RenderFSAASamples           0   0
 RenderReflectionsEnabled    0   0
 RenderReflectionProbeDetail	0	0
 
+list TexUnit16orLess
+RenderTerrainPBRDetail      1   -1
diff --git a/indra/newview/featuretable_mac.txt b/indra/newview/featuretable_mac.txt
index 40aaccc8cb..ac0ac15bd0 100644
--- a/indra/newview/featuretable_mac.txt
+++ b/indra/newview/featuretable_mac.txt
@@ -45,6 +45,7 @@ RenderObjectBump			1	1
 RenderLocalLightCount		1	4096
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	1.0
 RenderVBOEnable				1	1
@@ -89,6 +90,7 @@ RenderLocalLightCount		1	8
 RenderMaxPartCount			1	0
 RenderTerrainDetail			1	0
 RenderTerrainLODFactor		1	1
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTransparentWater		1	0
 RenderTreeLODFactor			1	0
 RenderVolumeLODFactor		1	1.125
@@ -118,6 +120,7 @@ RenderMaxPartCount			1	2048
 RenderLocalLightCount		1	256
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	1.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.125
@@ -147,6 +150,7 @@ RenderMaxPartCount			1	4096
 RenderLocalLightCount		1	512
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.25
@@ -176,6 +180,7 @@ RenderMaxPartCount			1	4096
 RenderLocalLightCount		1	1024
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   1
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.375
@@ -205,6 +210,7 @@ RenderMaxPartCount			1	4096
 RenderLocalLightCount		1	2048
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.5
@@ -234,6 +240,7 @@ RenderMaxPartCount			1	4096
 RenderLocalLightCount		1	4096
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	0.5
 RenderVolumeLODFactor		1	1.75
@@ -262,6 +269,7 @@ RenderLocalLightCount		1	8192
 RenderMaxPartCount			1	8192
 RenderTerrainDetail			1	1
 RenderTerrainLODFactor		1	2.0
+RenderTerrainPBRPlanarSampleCount 1   3
 RenderTransparentWater		1	1
 RenderTreeLODFactor			1	1.0
 RenderVolumeLODFactor		1	2.0
@@ -308,6 +316,9 @@ RenderShadowDetail			0	0
 list TexUnit8orLess
 RenderDeferredSSAO			0	0
 
+list TexUnit16orLess
+RenderTerrainPBRDetail      1   -1
+
 list AMD
 RenderDeferredSSAO			1	0
 
diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index e6a47f1c64..28dd2a3c9a 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -229,6 +229,7 @@
 #include "pipeline.h"
 #include "llgesturemgr.h"
 #include "llsky.h"
+#include "llvlcomposition.h"
 #include "llvlmanager.h"
 #include "llviewercamera.h"
 #include "lldrawpoolbump.h"
diff --git a/indra/newview/lldrawpool.h b/indra/newview/lldrawpool.h
index 0a9c2cc420..c69f386c6d 100644
--- a/indra/newview/lldrawpool.h
+++ b/indra/newview/lldrawpool.h
@@ -58,9 +58,9 @@ public:
 		POOL_SIMPLE,
 		POOL_FULLBRIGHT,
 		POOL_BUMP,
-		POOL_TERRAIN,
         POOL_MATERIALS,
         POOL_GLTF_PBR,
+		POOL_TERRAIN,
         POOL_GRASS,
         POOL_GLTF_PBR_ALPHA_MASK,
 		POOL_TREE,
diff --git a/indra/newview/lldrawpoolterrain.cpp b/indra/newview/lldrawpoolterrain.cpp
index 43f7587591..fc8e9fcfe5 100644
--- a/indra/newview/lldrawpoolterrain.cpp
+++ b/indra/newview/lldrawpoolterrain.cpp
@@ -54,8 +54,11 @@
 const F32 DETAIL_SCALE = 1.f/16.f;
 int DebugDetailMap = 0;
 
-S32 LLDrawPoolTerrain::sDetailMode = 1;
+const S32 PBR_DETAIL_EMISSIVE = 0;
+
+S32 LLDrawPoolTerrain::sPBRDetailMode = 0;
 F32 LLDrawPoolTerrain::sDetailScale = DETAIL_SCALE;
+F32 LLDrawPoolTerrain::sPBRDetailScale = DETAIL_SCALE;
 static LLGLSLShader* sShader = NULL;
 static LLTrace::BlockTimerStatHandle FTM_SHADOW_TERRAIN("Terrain Shadow");
 
@@ -66,7 +69,8 @@ LLDrawPoolTerrain::LLDrawPoolTerrain(LLViewerTexture *texturep) :
 {
 	// Hack!
 	sDetailScale = 1.f/gSavedSettings.getF32("RenderTerrainScale");
-	sDetailMode = gSavedSettings.getS32("RenderTerrainDetail");
+	sPBRDetailScale = 1.f/gSavedSettings.getF32("RenderTerrainPBRScale");
+	sPBRDetailMode = gSavedSettings.getS32("RenderTerrainPBRDetail");
 	mAlphaRampImagep = LLViewerTextureManager::getFetchedTexture(IMG_ALPHA_GRAD);
 
 	//gGL.getTexUnit(0)->bind(mAlphaRampImagep.get());
@@ -105,13 +109,7 @@ U32 LLDrawPoolTerrain::getVertexDataMask()
 
 void LLDrawPoolTerrain::prerender()
 {
-	sDetailMode = gSavedSettings.getS32("RenderTerrainDetail");
-}
-
-//static
-S32 LLDrawPoolTerrain::getDetailMode()
-{
-	return sDetailMode;
+    sPBRDetailMode = gSavedSettings.getS32("RenderTerrainPBRDetail");
 }
 
 void LLDrawPoolTerrain::boostTerrainDetailTextures()
@@ -121,8 +119,36 @@ void LLDrawPoolTerrain::boostTerrainDetailTextures()
 	LLVLComposition *compp = regionp->getComposition();
 	for (S32 i = 0; i < 4; i++)
 	{
-		compp->mDetailTextures[i]->setBoostLevel(LLGLTexture::BOOST_TERRAIN);
-        compp->mDetailTextures[i]->addTextureStats(1024.f * 1024.f);
+        constexpr LLGLTexture::EBoostLevel level = LLGLTexture::BOOST_TERRAIN;
+        constexpr float stats = 1024.f * 1024.f;
+
+        LLPointer<LLViewerFetchedTexture>& tex = compp->mDetailTextures[i];
+        llassert(tex.notNull());
+		tex->setBoostLevel(level);
+        tex->addTextureStats(stats);
+
+        LLPointer<LLFetchedGLTFMaterial>& mat = compp->mDetailMaterials[i];
+        llassert(mat.notNull());
+        if (mat->mBaseColorTexture)
+        {
+            mat->mBaseColorTexture->setBoostLevel(level);
+            mat->mBaseColorTexture->addTextureStats(stats);
+        }
+        if (mat->mNormalTexture)
+        {
+            mat->mNormalTexture->setBoostLevel(level);
+            mat->mNormalTexture->addTextureStats(stats);
+        }
+        if (mat->mMetallicRoughnessTexture)
+        {
+            mat->mMetallicRoughnessTexture->setBoostLevel(level);
+            mat->mMetallicRoughnessTexture->addTextureStats(stats);
+        }
+        if (mat->mEmissiveTexture)
+        {
+            mat->mEmissiveTexture->setBoostLevel(level);
+            mat->mEmissiveTexture->addTextureStats(stats);
+        }
 	}
 }
 
@@ -130,10 +156,6 @@ void LLDrawPoolTerrain::beginDeferredPass(S32 pass)
 {
 	LL_PROFILE_ZONE_SCOPED_CATEGORY_DRAWPOOL; //LL_RECORD_BLOCK_TIME(FTM_RENDER_TERRAIN);
 	LLFacePool::beginRenderPass(pass);
-
-	sShader = &gDeferredTerrainProgram;
-
-	sShader->bind();
 }
 
 void LLDrawPoolTerrain::endDeferredPass(S32 pass)
@@ -214,9 +236,34 @@ void LLDrawPoolTerrain::drawLoop()
 
 void LLDrawPoolTerrain::renderFullShader()
 {
+    const BOOL use_local_materials = gLocalTerrainMaterials.materialsReady(TRUE);
+	// Hack! Get the region that this draw pool is rendering from!
+	LLViewerRegion *regionp = mDrawFace[0]->getDrawable()->getVObj()->getRegion();
+	LLVLComposition *compp = regionp->getComposition();
+    const BOOL use_textures = !use_local_materials && (compp->getMaterialType() == LLTerrainMaterials::Type::TEXTURE);
+    
+    if (use_textures)
+    {
+        // Use textures
+        sShader = &gDeferredTerrainProgram;
+        sShader->bind();
+        renderFullShaderTextures();
+    }
+    else
+    {
+        // Use materials
+        sShader = &gDeferredPBRTerrainProgram;
+        sShader->bind();
+        renderFullShaderPBR(use_local_materials);
+    }
+}
+
+void LLDrawPoolTerrain::renderFullShaderTextures()
+{
 	// Hack! Get the region that this draw pool is rendering from!
 	LLViewerRegion *regionp = mDrawFace[0]->getDrawable()->getVObj()->getRegion();
 	LLVLComposition *compp = regionp->getComposition();
+
 	LLViewerTexture *detail_texture0p = compp->mDetailTextures[0];
 	LLViewerTexture *detail_texture1p = compp->mDetailTextures[1];
 	LLViewerTexture *detail_texture2p = compp->mDetailTextures[2];
@@ -311,6 +358,197 @@ void LLDrawPoolTerrain::renderFullShader()
 	gGL.getTexUnit(detail0)->activate();
 }
 
+// *TODO: Investigate use of bindFast for PBR terrain textures
+void LLDrawPoolTerrain::renderFullShaderPBR(BOOL local_materials)
+{
+	// Hack! Get the region that this draw pool is rendering from!
+	LLViewerRegion *regionp = mDrawFace[0]->getDrawable()->getVObj()->getRegion();
+	LLVLComposition *compp = regionp->getComposition();
+	LLPointer<LLFetchedGLTFMaterial> (*materials)[LLVLComposition::ASSET_COUNT] = &compp->mDetailMaterials;
+
+    if (local_materials)
+    {
+        // Override region terrain with the global local override terrain
+        materials = &gLocalTerrainMaterials.mDetailMaterials;
+    }
+
+    constexpr U32 terrain_material_count = 1 + LLViewerShaderMgr::TERRAIN_DETAIL3_BASE_COLOR - LLViewerShaderMgr::TERRAIN_DETAIL0_BASE_COLOR;
+    S32 detail_basecolor[terrain_material_count];
+    S32 detail_normal[terrain_material_count];
+    S32 detail_metalrough[terrain_material_count];
+    S32 detail_emissive[terrain_material_count];
+
+    for (U32 i = 0; i < terrain_material_count; ++i)
+    {
+		const LLFetchedGLTFMaterial* material = (*materials)[i].get();
+
+        LLViewerTexture *detail_basecolor_texturep = material->mBaseColorTexture;
+        LLViewerTexture *detail_normal_texturep = material->mNormalTexture;
+        LLViewerTexture *detail_metalrough_texturep = material->mMetallicRoughnessTexture;
+        LLViewerTexture *detail_emissive_texturep = material->mEmissiveTexture;
+
+        detail_basecolor[i] = sShader->enableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_BASE_COLOR + i);
+        if (detail_basecolor_texturep)
+        {
+            gGL.getTexUnit(detail_basecolor[i])->bind(detail_basecolor_texturep);
+        }
+        else
+        {
+            gGL.getTexUnit(detail_basecolor[i])->bind(LLViewerFetchedTexture::sWhiteImagep);
+        }
+        gGL.getTexUnit(detail_basecolor[i])->setTextureAddressMode(LLTexUnit::TAM_WRAP);
+        gGL.getTexUnit(detail_basecolor[i])->activate();
+
+        detail_normal[i] = sShader->enableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_NORMAL + i);
+        if (detail_normal_texturep)
+        {
+            gGL.getTexUnit(detail_normal[i])->bind(detail_normal_texturep);
+        }
+        else
+        {
+            gGL.getTexUnit(detail_normal[i])->bind(LLViewerFetchedTexture::sFlatNormalImagep);
+        }
+        gGL.getTexUnit(detail_normal[i])->setTextureAddressMode(LLTexUnit::TAM_WRAP);
+        gGL.getTexUnit(detail_normal[i])->activate();
+
+        detail_metalrough[i] = sShader->enableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_METALLIC_ROUGHNESS + i);
+        if (detail_metalrough_texturep)
+        {
+            gGL.getTexUnit(detail_metalrough[i])->bind(detail_metalrough_texturep);
+        }
+        else
+        {
+            gGL.getTexUnit(detail_metalrough[i])->bind(LLViewerFetchedTexture::sWhiteImagep);
+        }
+        gGL.getTexUnit(detail_metalrough[i])->setTextureAddressMode(LLTexUnit::TAM_WRAP);
+        gGL.getTexUnit(detail_metalrough[i])->activate();
+
+        if (sPBRDetailMode >= PBR_DETAIL_EMISSIVE)
+        {
+            detail_emissive[i] = sShader->enableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_EMISSIVE + i);
+            if (detail_emissive_texturep)
+            {
+                gGL.getTexUnit(detail_emissive[i])->bind(detail_emissive_texturep);
+            }
+            else
+            {
+                gGL.getTexUnit(detail_emissive[i])->bind(LLViewerFetchedTexture::sWhiteImagep);
+            }
+            gGL.getTexUnit(detail_emissive[i])->setTextureAddressMode(LLTexUnit::TAM_WRAP);
+            gGL.getTexUnit(detail_emissive[i])->activate();
+        }
+    }
+
+	LLGLSLShader* shader = LLGLSLShader::sCurBoundShaderPtr;
+	llassert(shader);
+		
+
+    // *TODO: Figure out why this offset is *sometimes* producing seams at the
+    // region edge, and repeat jumps when crossing regions, when
+    // RenderTerrainPBRScale is not a factor of the region scale.
+	LLVector3d region_origin_global = gAgent.getRegion()->getOriginGlobal();
+	F32 offset_x = (F32)fmod(region_origin_global.mdV[VX], 1.0/(F64)sPBRDetailScale)*sPBRDetailScale;
+	F32 offset_y = (F32)fmod(region_origin_global.mdV[VY], 1.0/(F64)sPBRDetailScale)*sPBRDetailScale;
+
+    LLGLTFMaterial::TextureTransform base_color_transform;
+    base_color_transform.mScale = LLVector2(sPBRDetailScale, sPBRDetailScale);
+    base_color_transform.mOffset = LLVector2(offset_x, offset_y);
+    F32 base_color_packed[8];
+    base_color_transform.getPacked(base_color_packed);
+    // *HACK: Use the same texture repeats for all PBR terrain textures for now
+    // (not compliant with KHR texture transform spec)
+    shader->uniform4fv(LLShaderMgr::TEXTURE_BASE_COLOR_TRANSFORM, 2, (F32*)base_color_packed);
+
+    LLSettingsWater::ptr_t pwater = LLEnvironment::instance().getCurrentWater();
+
+	//
+	// Alpha Ramp 
+	//
+	S32 alpha_ramp = sShader->enableTexture(LLViewerShaderMgr::TERRAIN_ALPHARAMP);
+	gGL.getTexUnit(alpha_ramp)->bind(m2DAlphaRampImagep);
+    gGL.getTexUnit(alpha_ramp)->setTextureAddressMode(LLTexUnit::TAM_CLAMP);
+
+    //
+    // GLTF uniforms
+    //
+
+    LLColor4 base_color_factors[terrain_material_count];
+    F32 metallic_factors[terrain_material_count];
+    F32 roughness_factors[terrain_material_count];
+    LLColor3 emissive_colors[terrain_material_count];
+    F32 minimum_alphas[terrain_material_count];
+    for (U32 i = 0; i < terrain_material_count; ++i)
+    {
+        const LLFetchedGLTFMaterial* material = (*materials)[i].get();
+
+        base_color_factors[i] = material->mBaseColor;
+        metallic_factors[i] = material->mMetallicFactor;
+        roughness_factors[i] = material->mRoughnessFactor;
+        emissive_colors[i] = material->mEmissiveColor;
+        // glTF 2.0 Specification 3.9.4. Alpha Coverage
+        // mAlphaCutoff is only valid for LLGLTFMaterial::ALPHA_MODE_MASK
+        // Use 0 here due to GLTF terrain blending (LLGLTFMaterial::bind uses
+        // -1 for easier debugging)
+        F32 min_alpha = -0.0f;
+        if (material->mAlphaMode == LLGLTFMaterial::ALPHA_MODE_MASK)
+        {
+            // dividing the alpha cutoff by transparency here allows the shader to compare against
+            // the alpha value of the texture without needing the transparency value
+            min_alpha = material->mAlphaCutoff/material->mBaseColor.mV[3];
+        }
+        minimum_alphas[i] = min_alpha;
+    }
+    shader->uniform4fv(LLShaderMgr::TERRAIN_BASE_COLOR_FACTORS, terrain_material_count, (F32*)base_color_factors);
+    shader->uniform4f(LLShaderMgr::TERRAIN_METALLIC_FACTORS, metallic_factors[0], metallic_factors[1], metallic_factors[2], metallic_factors[3]);
+    shader->uniform4f(LLShaderMgr::TERRAIN_ROUGHNESS_FACTORS, roughness_factors[0], roughness_factors[1], roughness_factors[2], roughness_factors[3]);
+    if (sPBRDetailMode >= PBR_DETAIL_EMISSIVE)
+    {
+        shader->uniform3fv(LLShaderMgr::TERRAIN_EMISSIVE_COLORS, terrain_material_count, (F32*)emissive_colors);
+    }
+    shader->uniform4f(LLShaderMgr::TERRAIN_MINIMUM_ALPHAS, minimum_alphas[0], minimum_alphas[1], minimum_alphas[2], minimum_alphas[3]);
+
+	// GL_BLEND disabled by default
+	drawLoop();
+
+	// Disable multitexture
+
+	sShader->disableTexture(LLViewerShaderMgr::TERRAIN_ALPHARAMP);
+
+	gGL.getTexUnit(alpha_ramp)->unbind(LLTexUnit::TT_TEXTURE);
+	gGL.getTexUnit(alpha_ramp)->disable();
+	gGL.getTexUnit(alpha_ramp)->activate();
+
+    for (U32 i = 0; i < terrain_material_count; ++i)
+    {
+        sShader->disableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_BASE_COLOR + i);
+        sShader->disableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_NORMAL + i);
+        sShader->disableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_METALLIC_ROUGHNESS + i);
+        if (sPBRDetailMode >= PBR_DETAIL_EMISSIVE)
+        {
+            sShader->disableTexture(LLViewerShaderMgr::TERRAIN_DETAIL0_EMISSIVE + i);
+        }
+
+        gGL.getTexUnit(detail_basecolor[i])->unbind(LLTexUnit::TT_TEXTURE);
+        gGL.getTexUnit(detail_basecolor[i])->disable();
+        gGL.getTexUnit(detail_basecolor[i])->activate();
+
+        gGL.getTexUnit(detail_normal[i])->unbind(LLTexUnit::TT_TEXTURE);
+        gGL.getTexUnit(detail_normal[i])->disable();
+        gGL.getTexUnit(detail_normal[i])->activate();
+
+        gGL.getTexUnit(detail_metalrough[i])->unbind(LLTexUnit::TT_TEXTURE);
+        gGL.getTexUnit(detail_metalrough[i])->disable();
+        gGL.getTexUnit(detail_metalrough[i])->activate();
+
+        if (sPBRDetailMode >= PBR_DETAIL_EMISSIVE)
+        {
+            gGL.getTexUnit(detail_emissive[i])->unbind(LLTexUnit::TT_TEXTURE);
+            gGL.getTexUnit(detail_emissive[i])->disable();
+            gGL.getTexUnit(detail_emissive[i])->activate();
+        }
+    }
+}
+
 void LLDrawPoolTerrain::hilightParcelOwners()
 {
 	{ //use fullbright shader for highlighting
diff --git a/indra/newview/lldrawpoolterrain.h b/indra/newview/lldrawpoolterrain.h
index 03bef31541..13f031c8e7 100644
--- a/indra/newview/lldrawpoolterrain.h
+++ b/indra/newview/lldrawpoolterrain.h
@@ -37,13 +37,12 @@ public:
     {
         VERTEX_DATA_MASK = LLVertexBuffer::MAP_VERTEX |
                     LLVertexBuffer::MAP_NORMAL |
+                    LLVertexBuffer::MAP_TANGENT | // Only PBR terrain uses this currently
                     LLVertexBuffer::MAP_TEXCOORD0 |
                     LLVertexBuffer::MAP_TEXCOORD1
 	};
 
 	virtual U32 getVertexDataMask();
-	static S32 getDetailMode();
-
 	LLDrawPoolTerrain(LLViewerTexture *texturep);
 	virtual ~LLDrawPoolTerrain();
 
@@ -67,8 +66,9 @@ public:
 	LLPointer<LLViewerTexture> m2DAlphaRampImagep;
 	LLPointer<LLViewerTexture> mAlphaNoiseImagep;
 
-	static S32 sDetailMode;
-	static F32 sDetailScale; // meters per texture
+	static S32 sPBRDetailMode;
+	static F32 sDetailScale; // textures per meter
+	static F32 sPBRDetailScale; // textures per meter
 
 protected:
     void boostTerrainDetailTextures();
@@ -79,6 +79,8 @@ protected:
 	void renderFull2TU();
 	void renderFull4TU();
 	void renderFullShader();
+	void renderFullShaderTextures();
+	void renderFullShaderPBR(BOOL local_materials = false);
 	void drawLoop();
 
 private:
diff --git a/indra/newview/llfeaturemanager.cpp b/indra/newview/llfeaturemanager.cpp
index f482d5a37d..9fff505c2a 100644
--- a/indra/newview/llfeaturemanager.cpp
+++ b/indra/newview/llfeaturemanager.cpp
@@ -664,6 +664,10 @@ void LLFeatureManager::applyBaseMasks()
 	{
 		maskFeatures("TexUnit8orLess");
 	}
+	if (gGLManager.mNumTextureImageUnits <= 16)
+	{
+		maskFeatures("TexUnit16orLess");
+	}
 	if (gGLManager.mVRAM > 512)
 	{
 		maskFeatures("VRAMGT512");
diff --git a/indra/newview/llfetchedgltfmaterial.cpp b/indra/newview/llfetchedgltfmaterial.cpp
index 90ec08391d..97b959e5cb 100644
--- a/indra/newview/llfetchedgltfmaterial.cpp
+++ b/indra/newview/llfetchedgltfmaterial.cpp
@@ -37,8 +37,6 @@
 LLFetchedGLTFMaterial::LLFetchedGLTFMaterial()
     : LLGLTFMaterial()
     , mExpectedFlusTime(0.f)
-    , mActive(true)
-    , mFetching(false)
 {
 
 }
@@ -242,10 +240,11 @@ void LLFetchedGLTFMaterial::onMaterialComplete(std::function<void()> material_co
     materialCompleteCallbacks.push_back(material_complete);
 }
 
-void LLFetchedGLTFMaterial::materialComplete()
+void LLFetchedGLTFMaterial::materialComplete(bool success)
 {
     llassert(mFetching);
     mFetching = false;
+    mFetchSuccess = success;
 
     for (std::function<void()> material_complete : materialCompleteCallbacks)
     {
diff --git a/indra/newview/llfetchedgltfmaterial.h b/indra/newview/llfetchedgltfmaterial.h
index 2559aa46cc..3fa4619d8c 100644
--- a/indra/newview/llfetchedgltfmaterial.h
+++ b/indra/newview/llfetchedgltfmaterial.h
@@ -49,6 +49,7 @@ public:
     void bind(LLViewerTexture* media_tex = nullptr);
 
     bool isFetching() const { return mFetching; }
+    bool isLoaded() const { return !mFetching && mFetchSuccess; }
 
     void addTextureEntry(LLTextureEntry* te) override;
     void removeTextureEntry(LLTextureEntry* te) override;
@@ -67,11 +68,12 @@ protected:
     // Lifetime management
     
     void materialBegin();
-    void materialComplete();
+    void materialComplete(bool success);
 
     F64 mExpectedFlusTime; // since epoch in seconds
-    bool mActive;
-    bool mFetching;
+    bool mActive = true;
+    bool mFetching = false;
+    bool mFetchSuccess = false;
     std::vector<std::function<void()>> materialCompleteCallbacks;
 };
 
diff --git a/indra/newview/llfloaterregioninfo.cpp b/indra/newview/llfloaterregioninfo.cpp
index d4eb40ff92..2c743d596e 100644
--- a/indra/newview/llfloaterregioninfo.cpp
+++ b/indra/newview/llfloaterregioninfo.cpp
@@ -605,6 +605,26 @@ LLPanelRegionEnvironment* LLFloaterRegionInfo::getPanelEnvironment()
 	return panel;
 }
 
+enum class TerrainMaterialType
+{
+    TEXTURE,
+    PBR_MATERIAL,
+    COUNT
+};
+
+TerrainMaterialType material_type_from_index(S32 index)
+{
+    if (index == 0)
+    {
+        return TerrainMaterialType::TEXTURE;
+    }
+    if (index == 1)
+    {
+        return TerrainMaterialType::PBR_MATERIAL;
+    }
+    return TerrainMaterialType::COUNT;
+}
+
 // static
 LLPanelRegionTerrainInfo* LLFloaterRegionInfo::getPanelRegionTerrain()
 {
@@ -1307,6 +1327,17 @@ void LLPanelRegionDebugInfo::onClickDebugConsole(void* data)
 
 BOOL LLPanelRegionTerrainInfo::validateTextureSizes()
 {
+    // *TODO: Don't early-exit in PBR material terrain editing mode, and
+    // instead do some reasonable checks that the PBR material is compatible
+    // with the terrain rendering pipeline. Err on the side of permissive.
+    LLComboBox* material_type_ctrl = getChild<LLComboBox>("terrain_material_type");
+    if (material_type_ctrl)
+    {
+        const TerrainMaterialType material_type = material_type_from_index(material_type_ctrl->getCurrentIndex());
+        const bool is_material_selected = material_type == TerrainMaterialType::PBR_MATERIAL;
+        if (is_material_selected) { return TRUE; }
+    }
+
     static const S32 MAX_TERRAIN_TEXTURE_SIZE = 1024;
 	for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
 	{
@@ -1324,7 +1355,7 @@ BOOL LLPanelRegionTerrainInfo::validateTextureSizes()
 
 		//LL_INFOS() << "texture detail " << i << " is " << width << "x" << height << "x" << components << LL_ENDL;
 
-		if (components != 3)
+		if (components != 3 && components != 4)
 		{
 			LLSD args;
 			args["TEXTURE_NUM"] = i+1;
@@ -1380,12 +1411,20 @@ BOOL LLPanelRegionTerrainInfo::postBuild()
 	initCtrl("terrain_raise_spin");
 	initCtrl("terrain_lower_spin");
 
+    getChild<LLUICtrl>("terrain_material_type")->setCommitCallback(boost::bind(&LLPanelRegionTerrainInfo::onSelectMaterialType, this));
+
 	std::string buffer;
+
 	for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
 	{
 		buffer = llformat("texture_detail_%d", i);
 		initCtrl(buffer);
 	}
+	for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+	{
+		buffer = llformat("material_detail_%d", i);
+		initCtrl(buffer);
+	}
 
 	for(S32 i = 0; i < CORNER_COUNT; ++i)
 	{
@@ -1402,10 +1441,78 @@ BOOL LLPanelRegionTerrainInfo::postBuild()
 	mAskedTextureHeights = false;
 	mConfirmedTextureHeights = false;
 
+    refresh();
+
 	return LLPanelRegionInfo::postBuild();
 }
 
 // virtual
+void LLPanelRegionTerrainInfo::refresh()
+{
+    // For simplicity, require restart
+    static BOOL feature_pbr_terrain_enabled = gSavedSettings.getBOOL("RenderTerrainPBREnabled");
+
+    LLTextBox* texture_text = getChild<LLTextBox>("detail_texture_text");
+    if (texture_text) { texture_text->setVisible(!feature_pbr_terrain_enabled); }
+
+    LLComboBox* material_type_ctrl = getChild<LLComboBox>("terrain_material_type");
+    if (material_type_ctrl)
+    {
+        material_type_ctrl->setVisible(feature_pbr_terrain_enabled);
+
+        bool has_material_assets = false;
+
+        std::string buffer;
+        for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+        {
+            buffer = llformat("material_detail_%d", i);
+            LLTextureCtrl* material_ctrl = getChild<LLTextureCtrl>(buffer);
+            if (material_ctrl && material_ctrl->getImageAssetID().notNull())
+            {
+                has_material_assets = true;
+                break;
+            }
+        }
+
+        TerrainMaterialType material_type = material_type_from_index(material_type_ctrl->getCurrentIndex());
+
+        if (!feature_pbr_terrain_enabled) { material_type = TerrainMaterialType::TEXTURE; }
+
+        const bool is_material_selected = material_type == TerrainMaterialType::PBR_MATERIAL;
+        material_type_ctrl->setEnabled(feature_pbr_terrain_enabled && !(is_material_selected && has_material_assets));
+    }
+}
+
+void LLPanelRegionTerrainInfo::onSelectMaterialType()
+{
+    LLComboBox* material_type_ctrl = getChild<LLComboBox>("terrain_material_type");
+    if (!material_type_ctrl) { return; }
+    const TerrainMaterialType material_type = material_type_from_index(material_type_ctrl->getCurrentIndex());
+    const bool show_texture_controls = material_type == TerrainMaterialType::TEXTURE;
+    const bool show_material_controls = material_type == TerrainMaterialType::PBR_MATERIAL;
+    std::string buffer;
+    LLTextureCtrl* texture_ctrl;
+    for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+    {
+        buffer = llformat("texture_detail_%d", i);
+        texture_ctrl = getChild<LLTextureCtrl>(buffer);
+        if (texture_ctrl)
+        {
+            texture_ctrl->setVisible(show_texture_controls);
+        }
+    }
+    for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+    {
+        buffer = llformat("material_detail_%d", i);
+        texture_ctrl = getChild<LLTextureCtrl>(buffer);
+        if (texture_ctrl)
+        {
+            texture_ctrl->setVisible(show_material_controls);
+        }
+    }
+}
+
+// virtual
 bool LLPanelRegionTerrainInfo::refreshFromRegion(LLViewerRegion* region)
 {
 	BOOL owner_or_god = gAgent.isGodlike() 
@@ -1421,18 +1528,30 @@ bool LLPanelRegionTerrainInfo::refreshFromRegion(LLViewerRegion* region)
 		getChild<LLUICtrl>("region_text")->setValue(LLSD(region->getName()));
 
 		LLVLComposition* compp = region->getComposition();
-		LLTextureCtrl* texture_ctrl;
+
+        // Are these 4 texture IDs or 4 material IDs? Who knows! Let's set the IDs on both pickers for now.
+		LLTextureCtrl* asset_ctrl;
 		std::string buffer;
 		for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
 		{
 			buffer = llformat("texture_detail_%d", i);
-			texture_ctrl = getChild<LLTextureCtrl>(buffer);
-			if(texture_ctrl)
+			asset_ctrl = getChild<LLTextureCtrl>(buffer);
+			if(asset_ctrl)
 			{
 				LL_DEBUGS() << "Detail Texture " << i << ": "
-						 << compp->getDetailTextureID(i) << LL_ENDL;
-				LLUUID tmp_id(compp->getDetailTextureID(i));
-				texture_ctrl->setImageAssetID(tmp_id);
+						 << compp->getDetailAssetID(i) << LL_ENDL;
+				LLUUID tmp_id(compp->getDetailAssetID(i));
+				asset_ctrl->setImageAssetID(tmp_id);
+			}
+		}
+		for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+		{
+			buffer = llformat("material_detail_%d", i);
+			asset_ctrl = getChild<LLTextureCtrl>(buffer);
+			if(asset_ctrl)
+			{
+				LLUUID tmp_id(compp->getDetailAssetID(i));
+				asset_ctrl->setImageAssetID(tmp_id);
 			}
 		}
 
@@ -1499,17 +1618,45 @@ BOOL LLPanelRegionTerrainInfo::sendUpdate()
 		}
 	}
 
-	LLTextureCtrl* texture_ctrl;
+	LLTextureCtrl* asset_ctrl;
 	std::string id_str;
 	LLMessageSystem* msg = gMessageSystem;
 
+    // Use material IDs instead of texture IDs if all material IDs are set, AND the mode is set to PBR materials.
+    S32 materials_used = 0;
+    LLComboBox* material_type_ctrl = getChild<LLComboBox>("terrain_material_type");
+    if (material_type_ctrl)
+    {
+        const TerrainMaterialType material_type = material_type_from_index(material_type_ctrl->getCurrentIndex());
+        const bool is_material_selected = material_type == TerrainMaterialType::PBR_MATERIAL;
+        if (is_material_selected)
+        {
+            for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
+            {
+                buffer = llformat("material_detail_%d", i);
+                asset_ctrl = getChild<LLTextureCtrl>(buffer);
+                if(asset_ctrl && asset_ctrl->getImageAssetID().notNull())
+                {
+                    ++materials_used;
+                }
+            }
+        }
+    }
 	for(S32 i = 0; i < TERRAIN_TEXTURE_COUNT; ++i)
 	{
-		buffer = llformat("texture_detail_%d", i);
-		texture_ctrl = getChild<LLTextureCtrl>(buffer);
-		if(texture_ctrl)
+        if (materials_used == TERRAIN_TEXTURE_COUNT)
+        {
+            buffer = llformat("material_detail_%d", i);
+            asset_ctrl = getChild<LLTextureCtrl>(buffer);
+        }
+        else
+        {
+            buffer = llformat("texture_detail_%d", i);
+            asset_ctrl = getChild<LLTextureCtrl>(buffer);
+        }
+		if(asset_ctrl)
 		{
-			LLUUID tmp_id(texture_ctrl->getImageAssetID());
+			LLUUID tmp_id(asset_ctrl->getImageAssetID());
 			tmp_id.toString(id_str);
 			buffer = llformat("%d %s", i, id_str.c_str());
 			strings.push_back(buffer);
diff --git a/indra/newview/llfloaterregioninfo.h b/indra/newview/llfloaterregioninfo.h
index 3eb39b250f..91fd54fcf9 100644
--- a/indra/newview/llfloaterregioninfo.h
+++ b/indra/newview/llfloaterregioninfo.h
@@ -75,9 +75,9 @@ class LLFloaterRegionInfo : public LLFloater
 public:
 
 
-	/*virtual*/ void onOpen(const LLSD& key);
-	/*virtual*/ void onClose(bool app_quitting);
-	/*virtual*/ BOOL postBuild();
+	void onOpen(const LLSD& key) override;
+	void onClose(bool app_quitting) override;
+	BOOL postBuild() override;
 
 	static void processEstateOwnerRequest(LLMessageSystem* msg, void**);
 
@@ -98,7 +98,7 @@ public:
 	static LLPanelRegionEnvironment* getPanelEnvironment();
 
 	// from LLPanel
-	virtual void refresh();
+	void refresh() override;
 	
 	void onRegionChanged();
 	void requestRegionInfo();
@@ -144,7 +144,7 @@ public:
 	virtual bool refreshFromRegion(LLViewerRegion* region);
 	virtual bool estateUpdate(LLMessageSystem* msg) { return true; }
 	
-	virtual BOOL postBuild();
+	BOOL postBuild() override;
 	virtual void updateChild(LLUICtrl* child_ctrl);
 	
 	void enableButton(const std::string& btn_name, BOOL enable = TRUE);
@@ -184,16 +184,15 @@ public:
 		:	LLPanelRegionInfo()	{}
 	~LLPanelRegionGeneralInfo() {}
 	
-	virtual bool refreshFromRegion(LLViewerRegion* region);
+	bool refreshFromRegion(LLViewerRegion* region) override;
 	
-	// LLPanel
-	virtual BOOL postBuild();
+	BOOL postBuild() override;
 	
 	void onBtnSet();
 	void setObjBonusFactor(F32 object_bonus_factor) {mObjBonusFactor = object_bonus_factor;}
 
 protected:
-	virtual BOOL sendUpdate();
+	BOOL sendUpdate() override;
 	void onClickKick();
 	void onKickCommit(const uuid_vec_t& ids);
 	static void onClickKickAll(void* userdata);
@@ -214,13 +213,13 @@ public:
 	LLPanelRegionDebugInfo()
 		:	LLPanelRegionInfo(), mTargetAvatar() {}
 	~LLPanelRegionDebugInfo() {}
-	// LLPanel
-	virtual BOOL postBuild();
+
+	BOOL postBuild() override;
 	
-	virtual bool refreshFromRegion(LLViewerRegion* region);
+	bool refreshFromRegion(LLViewerRegion* region) override;
 	
 protected:
-	virtual BOOL sendUpdate();
+	BOOL sendUpdate() override;
 
 	void onClickChooseAvatar();
 	void callbackAvatarID(const uuid_vec_t& ids, const std::vector<LLAvatarName> names);
@@ -247,9 +246,9 @@ public:
 	LLPanelRegionTerrainInfo() : LLPanelRegionInfo() {}
 	~LLPanelRegionTerrainInfo() {}
 	
-	virtual BOOL postBuild();												// LLPanel
+	BOOL postBuild() override;
 	
-	virtual bool refreshFromRegion(LLViewerRegion* region);					// refresh local settings from region update from simulator
+    bool refreshFromRegion(LLViewerRegion* region) override;                // refresh local settings from region update from simulator
 	void setEnvControls(bool available);									// Whether environment settings are available for this region
 
 	BOOL validateTextureSizes();
@@ -257,7 +256,8 @@ public:
 
 	//static void onChangeAnything(LLUICtrl* ctrl, void* userData);			// callback for any change, to enable commit button
 	
-	virtual BOOL sendUpdate();
+    void refresh() override;
+    void onSelectMaterialType();
 
 	static void onClickDownloadRaw(void*);
 	static void onClickUploadRaw(void*);
@@ -265,6 +265,9 @@ public:
 	bool callbackBakeTerrain(const LLSD& notification, const LLSD& response);
 	bool callbackTextureHeights(const LLSD& notification, const LLSD& response);
 
+protected:
+	BOOL sendUpdate() override;
+
 private:
 	bool mConfirmedTextureHeights;
 	bool mAskedTextureHeights;
@@ -303,13 +306,12 @@ public:
 	static void updateEstateName(const std::string& name);
 	static void updateEstateOwnerName(const std::string& name);
 
-	virtual bool refreshFromRegion(LLViewerRegion* region);
-	virtual bool estateUpdate(LLMessageSystem* msg);
+	bool refreshFromRegion(LLViewerRegion* region) override;
+	bool estateUpdate(LLMessageSystem* msg) override;
 	
-	// LLPanel
-	virtual BOOL postBuild();
-	virtual void updateChild(LLUICtrl* child_ctrl);
-	virtual void refresh();
+	BOOL postBuild() override;
+	void updateChild(LLUICtrl* child_ctrl) override;
+	void refresh() override;
 
 	void refreshFromEstate();
 	
@@ -319,7 +321,7 @@ public:
 	void setOwnerName(const std::string& name);
 
 protected:
-	virtual BOOL sendUpdate();
+	BOOL sendUpdate() override;
 	// confirmation dialog callback
 	bool callbackChangeLindenEstate(const LLSD& notification, const LLSD& response);
 
@@ -339,17 +341,16 @@ public:
 	LLPanelEstateCovenant();
 	~LLPanelEstateCovenant() {}
 	
-	// LLPanel
-	virtual BOOL postBuild();
-	virtual void updateChild(LLUICtrl* child_ctrl);
-	virtual bool refreshFromRegion(LLViewerRegion* region);
-	virtual bool estateUpdate(LLMessageSystem* msg);
+	BOOL postBuild() override;
+	void updateChild(LLUICtrl* child_ctrl) override;
+	bool refreshFromRegion(LLViewerRegion* region) override;
+	bool estateUpdate(LLMessageSystem* msg) override;
 
 	// LLView overrides
 	BOOL handleDragAndDrop(S32 x, S32 y, MASK mask,
 						   BOOL drop, EDragAndDropType cargo_type,
 						   void *cargo_data, EAcceptance *accept,
-						   std::string& tooltip_msg);
+						   std::string& tooltip_msg) override;
 	static bool confirmChangeCovenantCallback(const LLSD& notification, const LLSD& response);
 	static void resetCovenantID(void* userdata);
 	static bool confirmResetCovenantCallback(const LLSD& notification, const LLSD& response);
@@ -382,7 +383,7 @@ public:
 	} EAssetStatus;
 
 protected:
-	virtual BOOL sendUpdate();
+	BOOL sendUpdate() override;
 	LLTextBox*				mEstateNameText;
 	LLTextBox*				mEstateOwnerText;
 	LLTextBox*				mLastModifiedText;
@@ -401,16 +402,19 @@ class LLPanelRegionExperiences : public LLPanelRegionInfo
 
 public:
 	LLPanelRegionExperiences(){}
-	/*virtual*/ BOOL postBuild();
-	virtual BOOL sendUpdate();
+	BOOL postBuild() override;
 	
 	static bool experienceCoreConfirm(const LLSD& notification, const LLSD& response);
 	static void sendEstateExperienceDelta(U32 flags, const LLUUID& agent_id);
 
 	static void infoCallback(LLHandle<LLPanelRegionExperiences> handle, const LLSD& content);
-	bool refreshFromRegion(LLViewerRegion* region);
+	bool refreshFromRegion(LLViewerRegion* region) override;
 	void sendPurchaseRequest()const;
 	void processResponse( const LLSD& content );
+
+protected:
+	BOOL sendUpdate() override;
+
 private:
 	void refreshRegionExperiences();
 
@@ -435,8 +439,8 @@ class LLPanelEstateAccess : public LLPanelRegionInfo
 public:
 	LLPanelEstateAccess();
 
-	virtual BOOL postBuild();
-	virtual void updateChild(LLUICtrl* child_ctrl);
+	BOOL postBuild() override;
+	void updateChild(LLUICtrl* child_ctrl) override;
 
 	void updateControls(LLViewerRegion* region);
 	void updateLists();
@@ -444,7 +448,7 @@ public:
 	void setPendingUpdate(bool pending) { mPendingUpdate = pending; }
 	bool getPendingUpdate() { return mPendingUpdate; }
 
-	virtual bool refreshFromRegion(LLViewerRegion* region);
+	bool refreshFromRegion(LLViewerRegion* region) override;
 
 private:
 	void onClickAddAllowedAgent();
diff --git a/indra/newview/llgltfmateriallist.cpp b/indra/newview/llgltfmateriallist.cpp
index 92c58a2dbc..a9216ae656 100644
--- a/indra/newview/llgltfmateriallist.cpp
+++ b/indra/newview/llgltfmateriallist.cpp
@@ -471,7 +471,7 @@ void LLGLTFMaterialList::onAssetLoadComplete(const LLUUID& id, LLAssetType::ETyp
     if (status != LL_ERR_NOERR)
     {
         LL_WARNS("GLTF") << "Error getting material asset data: " << LLAssetStorage::getErrorString(status) << " (" << status << ")" << LL_ENDL;
-        asset_data->mMaterial->materialComplete();
+        asset_data->mMaterial->materialComplete(false);
         delete asset_data;
     }
     else
@@ -556,7 +556,7 @@ void LLGLTFMaterialList::onAssetLoadComplete(const LLUUID& id, LLAssetType::ETyp
                 LL_DEBUGS("GLTF") << "Failed to get material " << id << LL_ENDL;
             }
 
-            asset_data->mMaterial->materialComplete();
+            asset_data->mMaterial->materialComplete(true);
 
             delete asset_data;
         });
diff --git a/indra/newview/llsurfacepatch.cpp b/indra/newview/llsurfacepatch.cpp
index 449d3d95c8..a6370e9ec2 100644
--- a/indra/newview/llsurfacepatch.cpp
+++ b/indra/newview/llsurfacepatch.cpp
@@ -221,7 +221,9 @@ void LLSurfacePatch::eval(const U32 x, const U32 y, const U32 stride, LLVector3
 	*vertex     = pos_agent-mVObjp->getRegion()->getOriginAgent();
 
 	LLVector3 rel_pos = pos_agent - mSurfacep->getOriginAgent();
-	LLVector3 tex_pos = rel_pos * (1.f/surface_stride);
+	// *NOTE: Only PBR terrain uses the UVs right now. Texture terrain just ignores it.
+    // *NOTE: In the future, UVs and horizontal position will no longer have a 1:1 relationship for PBR terrain
+	LLVector3 tex_pos = rel_pos;
 	tex0->mV[0]  = tex_pos.mV[0];
 	tex0->mV[1]  = tex_pos.mV[1];
 	tex1->mV[0] = mSurfacep->getRegion()->getCompositionXY(llfloor(mOriginRegion.mV[0])+x, llfloor(mOriginRegion.mV[1])+y);
@@ -739,7 +741,7 @@ void LLSurfacePatch::updateGL()
 	
 	updateCompositionStats();
 	F32 tex_patch_size = meters_per_grid*grids_per_patch_edge;
-	if (comp->generateTexture((F32)origin_region[VX], (F32)origin_region[VY],
+	if (comp->generateMinimapTileLand((F32)origin_region[VX], (F32)origin_region[VY],
 							  tex_patch_size, tex_patch_size))
 	{
 		mSTexUpdate = FALSE;
diff --git a/indra/newview/lltexturectrl.cpp b/indra/newview/lltexturectrl.cpp
index b9cb00b561..916c0194c2 100644
--- a/indra/newview/lltexturectrl.cpp
+++ b/indra/newview/lltexturectrl.cpp
@@ -1654,7 +1654,7 @@ LLTextureCtrl::LLTextureCtrl(const LLTextureCtrl::Params& p)
 	mShowLoadingPlaceholder( TRUE ),
 	mOpenTexPreview(false),
     mBakeTextureEnabled(true),
-    mInventoryPickType(PICK_TEXTURE),
+    mInventoryPickType(p.pick_type),
 	mImageAssetID(p.image_id),
 	mDefaultImageAssetID(p.default_image_id),
 	mDefaultImageName(p.default_image_name),
@@ -2406,6 +2406,16 @@ LLSD LLTextureCtrl::getValue() const
 	return LLSD(getImageAssetID());
 }
 
+namespace LLInitParam
+{
+    void TypeValues<EPickInventoryType>::declareValues()
+    {
+        declare("texture_material", PICK_TEXTURE_MATERIAL);
+        declare("texture", PICK_TEXTURE);
+        declare("material", PICK_MATERIAL);
+    }
+}
+
 
 
 
diff --git a/indra/newview/lltexturectrl.h b/indra/newview/lltexturectrl.h
index 77919637ac..05ea185b1b 100644
--- a/indra/newview/lltexturectrl.h
+++ b/indra/newview/lltexturectrl.h
@@ -64,13 +64,6 @@ bool get_is_predefined_texture(LLUUID asset_id);
 LLUUID get_copy_free_item_by_asset_id(LLUUID image_id, bool no_trans_perm = false);
 bool get_can_copy_texture(LLUUID image_id);
 
-enum LLPickerSource
-{
-    PICKER_INVENTORY,
-    PICKER_LOCAL,
-    PICKER_BAKE,
-    PICKER_UNKNOWN, // on cancel, default ids
-};
 
 typedef enum e_pick_inventory_type
 {
@@ -79,6 +72,23 @@ typedef enum e_pick_inventory_type
     PICK_MATERIAL = 2,
 } EPickInventoryType;
 
+namespace LLInitParam
+{
+    template<>
+	struct TypeValues<EPickInventoryType> : public TypeValuesHelper<EPickInventoryType>
+	{
+		static void declareValues();
+	};
+}
+
+enum LLPickerSource
+{
+    PICKER_INVENTORY,
+    PICKER_LOCAL,
+    PICKER_BAKE,
+    PICKER_UNKNOWN, // on cancel, default ids
+};
+
 //////////////////////////////////////////////////////////////////////////////////////////
 // LLTextureCtrl
 
@@ -100,6 +110,7 @@ public:
 		Optional<LLUUID>		image_id;
 		Optional<LLUUID>		default_image_id;
 		Optional<std::string>	default_image_name;
+        Optional<EPickInventoryType> pick_type;
 		Optional<bool>			allow_no_texture;
 		Optional<bool>			can_apply_immediately;
 		Optional<bool>			no_commit_on_selection; // alternative mode: commit occurs and the widget gets dirty
@@ -117,6 +128,7 @@ public:
 		:	image_id("image"),
 			default_image_id("default_image_id"),
 			default_image_name("default_image_name"),
+            pick_type("pick_type", PICK_TEXTURE),
 			allow_no_texture("allow_no_texture", false),
 			can_apply_immediately("can_apply_immediately"),
 			no_commit_on_selection("no_commit_on_selection", false),
diff --git a/indra/newview/llviewercontrol.cpp b/indra/newview/llviewercontrol.cpp
index 7738cb904e..ba1add9b92 100644
--- a/indra/newview/llviewercontrol.cpp
+++ b/indra/newview/llviewercontrol.cpp
@@ -54,6 +54,7 @@
 #include "llvotree.h"
 #include "llvovolume.h"
 #include "llworld.h"
+#include "llvlcomposition.h"
 #include "pipeline.h"
 #include "llviewerjoystick.h"
 #include "llviewerobjectlist.h"
@@ -117,12 +118,25 @@ static bool handleRenderFarClipChanged(const LLSD& newvalue)
     return false;
 }
 
-static bool handleTerrainDetailChanged(const LLSD& newvalue)
+static bool handleTerrainScaleChanged(const LLSD& newvalue)
 {
-	LLDrawPoolTerrain::sDetailMode = newvalue.asInteger();
+    F64 scale = newvalue.asReal();
+    if (scale != 0.0)
+    {
+        LLDrawPoolTerrain::sDetailScale = F32(1.0 / scale);
+    }
 	return true;
 }
 
+static bool handlePBRTerrainScaleChanged(const LLSD& newvalue)
+{
+    F64 scale = newvalue.asReal();
+    if (scale != 0.0)
+    {
+        LLDrawPoolTerrain::sPBRDetailScale = F32(1.0 / scale);
+    }
+	return true;
+}
 
 static bool handleDebugAvatarJointsChanged(const LLSD& newvalue)
 {
@@ -650,6 +664,16 @@ void handleFPSTuningStrategyChanged(const LLSD& newValue)
     const auto newval = gSavedSettings.getU32("TuningFPSStrategy");
     LLPerfStats::tunables.userFPSTuningStrategy = newval;
 }
+
+void handleLocalTerrainChanged(const LLSD& newValue)
+{
+    for (U32 i = 0; i < LLTerrainMaterials::ASSET_COUNT; ++i)
+    {
+        const auto setting = gSavedSettings.getString(std::string("LocalTerrainAsset") + std::to_string(i + 1));
+        const LLUUID materialID(setting);
+        gLocalTerrainMaterials.setDetailAssetID(i, materialID);
+    }
+}
 ////////////////////////////////////////////////////////////////////////////
 
 LLPointer<LLControlVariable> setting_get_control(LLControlGroup& group, const std::string& setting)
@@ -684,7 +708,11 @@ void settings_setup_listeners()
 {
     setting_setup_signal_listener(gSavedSettings, "FirstPersonAvatarVisible", handleRenderAvatarMouselookChanged);
     setting_setup_signal_listener(gSavedSettings, "RenderFarClip", handleRenderFarClipChanged);
-    setting_setup_signal_listener(gSavedSettings, "RenderTerrainDetail", handleTerrainDetailChanged);
+    setting_setup_signal_listener(gSavedSettings, "RenderTerrainScale", handleTerrainScaleChanged);
+    setting_setup_signal_listener(gSavedSettings, "RenderTerrainPBRScale", handlePBRTerrainScaleChanged);
+    setting_setup_signal_listener(gSavedSettings, "RenderTerrainPBRDetail", handleSetShaderChanged);
+    setting_setup_signal_listener(gSavedSettings, "RenderTerrainPBRPlanarSampleCount", handleSetShaderChanged);
+    setting_setup_signal_listener(gSavedSettings, "RenderTerrainPBRTriplanarBlendFactor", handleSetShaderChanged);
     setting_setup_signal_listener(gSavedSettings, "OctreeStaticObjectSizeFactor", handleRepartition);
     setting_setup_signal_listener(gSavedSettings, "OctreeDistanceFactor", handleRepartition);
     setting_setup_signal_listener(gSavedSettings, "OctreeMaxNodeCapacity", handleRepartition);
@@ -830,6 +858,10 @@ void settings_setup_listeners()
     setting_setup_signal_listener(gSavedSettings, "AutoTuneImpostorFarAwayDistance", handleUserImpostorDistanceChanged);
     setting_setup_signal_listener(gSavedSettings, "AutoTuneImpostorByDistEnabled", handleUserImpostorByDistEnabledChanged);
     setting_setup_signal_listener(gSavedSettings, "TuningFPSStrategy", handleFPSTuningStrategyChanged);
+    setting_setup_signal_listener(gSavedSettings, "LocalTerrainAsset1", handleLocalTerrainChanged);
+    setting_setup_signal_listener(gSavedSettings, "LocalTerrainAsset2", handleLocalTerrainChanged);
+    setting_setup_signal_listener(gSavedSettings, "LocalTerrainAsset3", handleLocalTerrainChanged);
+    setting_setup_signal_listener(gSavedSettings, "LocalTerrainAsset4", handleLocalTerrainChanged);
 
     setting_setup_signal_listener(gSavedPerAccountSettings, "AvatarHoverOffsetZ", handleAvatarHoverOffsetChanged);
 }
diff --git a/indra/newview/llviewerregion.cpp b/indra/newview/llviewerregion.cpp
index 60862ae5bd..dae476d9d7 100755
--- a/indra/newview/llviewerregion.cpp
+++ b/indra/newview/llviewerregion.cpp
@@ -2963,20 +2963,20 @@ void LLViewerRegion::unpackRegionHandshake()
 
 		// Get the 4 textures for land
 		msg->getUUID("RegionInfo", "TerrainDetail0", tmp_id);
-		changed |= (tmp_id != compp->getDetailTextureID(0));		
-		compp->setDetailTextureID(0, tmp_id);
+		changed |= (tmp_id != compp->getDetailAssetID(0));		
+		compp->setDetailAssetID(0, tmp_id);
 
 		msg->getUUID("RegionInfo", "TerrainDetail1", tmp_id);
-		changed |= (tmp_id != compp->getDetailTextureID(1));		
-		compp->setDetailTextureID(1, tmp_id);
+		changed |= (tmp_id != compp->getDetailAssetID(1));		
+		compp->setDetailAssetID(1, tmp_id);
 
 		msg->getUUID("RegionInfo", "TerrainDetail2", tmp_id);
-		changed |= (tmp_id != compp->getDetailTextureID(2));		
-		compp->setDetailTextureID(2, tmp_id);
+		changed |= (tmp_id != compp->getDetailAssetID(2));		
+		compp->setDetailAssetID(2, tmp_id);
 
 		msg->getUUID("RegionInfo", "TerrainDetail3", tmp_id);
-		changed |= (tmp_id != compp->getDetailTextureID(3));		
-		compp->setDetailTextureID(3, tmp_id);
+		changed |= (tmp_id != compp->getDetailAssetID(3));		
+		compp->setDetailAssetID(3, tmp_id);
 
 		// Get the start altitude and range values for land textures
 		F32 tmp_f32;
diff --git a/indra/newview/llviewershadermgr.cpp b/indra/newview/llviewershadermgr.cpp
index 3225299493..6495692e9a 100644
--- a/indra/newview/llviewershadermgr.cpp
+++ b/indra/newview/llviewershadermgr.cpp
@@ -69,6 +69,14 @@ bool				LLViewerShaderMgr::sSkipReload = false;
 
 LLVector4			gShinyOrigin;
 
+S32 clamp_terrain_mapping(S32 mapping)
+{
+    // 1 = "flat", 2 not implemented, 3 = triplanar mapping
+    mapping = llclamp(mapping, 1, 3);
+    if (mapping == 2) { mapping = 1; }
+    return mapping;
+}
+
 //utility shaders
 LLGLSLShader	gOcclusionProgram;
 LLGLSLShader    gSkinnedOcclusionProgram;
@@ -214,6 +222,7 @@ LLGLSLShader            gDeferredSkinnedPBROpaqueProgram;
 LLGLSLShader            gHUDPBRAlphaProgram;
 LLGLSLShader            gDeferredPBRAlphaProgram;
 LLGLSLShader            gDeferredSkinnedPBRAlphaProgram;
+LLGLSLShader			gDeferredPBRTerrainProgram;
 
 //helper for making a rigged variant of a given shader
 bool make_rigged_variant(LLGLSLShader& shader, LLGLSLShader& riggedShader)
@@ -271,7 +280,7 @@ LLViewerShaderMgr::LLViewerShaderMgr() :
 	mShaderList.push_back(&gDeferredEmissiveProgram);
     mShaderList.push_back(&gDeferredSkinnedEmissiveProgram);
 	mShaderList.push_back(&gDeferredAvatarEyesProgram);
-    mShaderList.push_back(&gDeferredAvatarAlphaProgram);
+	mShaderList.push_back(&gDeferredAvatarAlphaProgram);
 	mShaderList.push_back(&gDeferredWLSkyProgram);
 	mShaderList.push_back(&gDeferredWLCloudProgram);
     mShaderList.push_back(&gDeferredWLMoonProgram);
@@ -623,6 +632,15 @@ std::string LLViewerShaderMgr::loadBasicShaders()
 		attribs["REF_SAMPLE_COUNT"] = "32";
 	}
 
+    { // PBR terrain
+        const S32 mapping = clamp_terrain_mapping(gSavedSettings.getS32("RenderTerrainPBRPlanarSampleCount"));
+        attribs["TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT"] = llformat("%d", mapping);
+        const F32 triplanar_factor = gSavedSettings.getF32("RenderTerrainPBRTriplanarBlendFactor");
+        attribs["TERRAIN_TRIPLANAR_BLEND_FACTOR"] = llformat("%.2f", triplanar_factor);
+        S32 detail = gSavedSettings.getS32("RenderTerrainPBRDetail");
+        attribs["TERRAIN_PBR_DETAIL"] = llformat("%d", detail);
+    }
+
 	LLGLSLShader::sGlobalDefines = attribs;
 
 	// We no longer have to bind the shaders to global glhandles, they are automatically added to a map now.
@@ -660,6 +678,7 @@ std::string LLViewerShaderMgr::loadBasicShaders()
 	index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/deferredUtil.glsl",                    1) );
 	index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/shadowUtil.glsl",                      1) );
 	index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/aoUtil.glsl",                          1) );
+	index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/pbrterrainUtilF.glsl",                 1) );
     index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/reflectionProbeF.glsl",                has_reflection_probes ? 3 : 2) );
     index_channels.push_back(-1);    shaders.push_back( make_pair( "deferred/screenSpaceReflUtil.glsl",             ssr ? 3 : 1) );
 	index_channels.push_back(-1);    shaders.push_back( make_pair( "lighting/lightNonIndexedF.glsl",                    mShaderLevel[SHADER_LIGHTING] ) );
@@ -951,6 +970,7 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
         gDeferredSkinnedPBROpaqueProgram.unload();
         gDeferredPBRAlphaProgram.unload();
         gDeferredSkinnedPBRAlphaProgram.unload();
+		gDeferredPBRTerrainProgram.unload();
 
 		return TRUE;
 	}
@@ -1242,6 +1262,34 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
         success = shader->createShader(NULL, NULL);
         llassert(success);
     }
+
+	if (success)
+	{
+        S32 detail = gSavedSettings.getS32("RenderTerrainPBRDetail");
+        detail = llclamp(detail, TERRAIN_PBR_DETAIL_MIN, TERRAIN_PBR_DETAIL_MAX);
+        const S32 mapping = clamp_terrain_mapping(gSavedSettings.getS32("RenderTerrainPBRPlanarSampleCount"));
+        gDeferredPBRTerrainProgram.mName = llformat("Deferred PBR Terrain Shader %d %s",
+                detail,
+                (mapping == 1 ? "flat" : "triplanar"));
+        gDeferredPBRTerrainProgram.mFeatures.encodesNormal = true;
+        gDeferredPBRTerrainProgram.mFeatures.hasSrgb = true;
+        gDeferredPBRTerrainProgram.mFeatures.isAlphaLighting = true;
+        gDeferredPBRTerrainProgram.mFeatures.disableTextureIndex = true; //hack to disable auto-setup of texture channels
+        gDeferredPBRTerrainProgram.mFeatures.calculatesAtmospherics = true;
+        gDeferredPBRTerrainProgram.mFeatures.hasAtmospherics = true;
+        gDeferredPBRTerrainProgram.mFeatures.hasGamma = true;
+        gDeferredPBRTerrainProgram.mFeatures.hasTransport = true;
+        gDeferredPBRTerrainProgram.mFeatures.isPBRTerrain = true;
+
+        gDeferredPBRTerrainProgram.mShaderFiles.clear();
+        gDeferredPBRTerrainProgram.mShaderFiles.push_back(make_pair("deferred/pbrterrainV.glsl", GL_VERTEX_SHADER));
+        gDeferredPBRTerrainProgram.mShaderFiles.push_back(make_pair("deferred/pbrterrainF.glsl", GL_FRAGMENT_SHADER));
+        gDeferredPBRTerrainProgram.mShaderLevel = mShaderLevel[SHADER_DEFERRED];
+        gDeferredPBRTerrainProgram.addPermutation("TERRAIN_PBR_DETAIL", llformat("%d", detail));
+        gDeferredPBRTerrainProgram.addPermutation("TERRAIN_PLANAR_TEXTURE_SAMPLE_COUNT", llformat("%d", mapping));
+        success = gDeferredPBRTerrainProgram.createShader(NULL, NULL);
+        llassert(success);
+	}
 	
 	if (success)
 	{
@@ -1955,8 +2003,6 @@ BOOL LLViewerShaderMgr::loadShadersDeferred()
 		gDeferredTerrainProgram.mName = "Deferred Terrain Shader";
 		gDeferredTerrainProgram.mFeatures.encodesNormal = true;
 		gDeferredTerrainProgram.mFeatures.hasSrgb = true;
-		gDeferredTerrainProgram.mFeatures.calculatesLighting = false;
-		gDeferredTerrainProgram.mFeatures.hasLighting = false;
 		gDeferredTerrainProgram.mFeatures.isAlphaLighting = true;
 		gDeferredTerrainProgram.mFeatures.disableTextureIndex = true; //hack to disable auto-setup of texture channels
 		gDeferredTerrainProgram.mFeatures.calculatesAtmospherics = true;
diff --git a/indra/newview/llviewershadermgr.h b/indra/newview/llviewershadermgr.h
index 04da7e48ae..cb1729cd1b 100644
--- a/indra/newview/llviewershadermgr.h
+++ b/indra/newview/llviewershadermgr.h
@@ -272,4 +272,16 @@ extern LLGLSLShader         gPBRGlowProgram;
 extern LLGLSLShader         gDeferredPBROpaqueProgram;
 extern LLGLSLShader         gDeferredPBRAlphaProgram;
 extern LLGLSLShader         gHUDPBRAlphaProgram;
+
+// Encodes detail level for dropping textures, in accordance with the GLTF spec
+// 0 is highest detail, -1 drops emissive, etc
+// https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#additional-textures
+enum TerrainPBRDetail : S32
+{
+    TERRAIN_PBR_DETAIL_MAX            = 0,
+    TERRAIN_PBR_DETAIL_EMISSIVE       = 0,
+    TERRAIN_PBR_DETAIL_OCCLUSION      = -1,
+    TERRAIN_PBR_DETAIL_MIN            = -1,
+};
+extern LLGLSLShader         gDeferredPBRTerrainProgram;
 #endif
diff --git a/indra/newview/llvlcomposition.cpp b/indra/newview/llvlcomposition.cpp
index 001fab7755..f645023217 100644
--- a/indra/newview/llvlcomposition.cpp
+++ b/indra/newview/llvlcomposition.cpp
@@ -34,12 +34,16 @@
 #include "lltextureview.h"
 #include "llviewertexture.h"
 #include "llviewertexturelist.h"
+#include "llfetchedgltfmaterial.h"
+#include "llgltfmateriallist.h"
 #include "llviewerregion.h"
 #include "noise.h"
 #include "llregionhandle.h" // for from_region_handle
 #include "llviewercontrol.h"
 
 
+static const U32 BASE_SIZE = 128;
+
 
 F32 bilinear(const F32 v00, const F32 v01, const F32 v10, const F32 v11, const F32 x_frac, const F32 y_frac)
 {
@@ -57,18 +61,199 @@ F32 bilinear(const F32 v00, const F32 v01, const F32 v10, const F32 v11, const F
 	return result;
 }
 
+LLTerrainMaterials::LLTerrainMaterials()
+{
+    for (S32 i = 0; i < ASSET_COUNT; ++i)
+    {
+        mMaterialTexturesSet[i] = false;
+    }
+}
 
-LLVLComposition::LLVLComposition(LLSurface *surfacep, const U32 width, const F32 scale) :
-	LLViewerLayer(width, scale),
-	mParamsReady(FALSE)
+LLTerrainMaterials::~LLTerrainMaterials()
 {
-	mSurfacep = surfacep;
+}
+
+BOOL LLTerrainMaterials::generateMaterials()
+{
+    if (texturesReady(TRUE))
+    {
+        return TRUE;
+    }
+
+    if (materialsReady(TRUE))
+    {
+        return TRUE;
+    }
+
+    return FALSE;
+}
+
+LLUUID LLTerrainMaterials::getDetailAssetID(S32 asset)
+{
+    llassert(mDetailTextures[asset] && mDetailMaterials[asset]);
+    // *HACK: Assume both the the material and texture were fetched in the same
+    // way using the same UUID. However, we may not know at this point which
+    // one will load.
+	return mDetailTextures[asset]->getID();
+}
+
+LLPointer<LLViewerFetchedTexture> fetch_terrain_texture(const LLUUID& id)
+{
+    if (id.isNull())
+    {
+        return nullptr;
+    }
+
+    LLPointer<LLViewerFetchedTexture> tex = LLViewerTextureManager::getFetchedTexture(id);
+    tex->setNoDelete();
+    return tex;
+}
+
+void LLTerrainMaterials::setDetailAssetID(S32 asset, const LLUUID& id)
+{
+	// This is terrain texture, but we are not setting it as BOOST_TERRAIN
+	// since we will be manipulating it later as needed.
+	mDetailTextures[asset] = fetch_terrain_texture(id);
+    LLPointer<LLFetchedGLTFMaterial>& mat = mDetailMaterials[asset];
+    mat = id.isNull() ? nullptr : gGLTFMaterialList.getMaterial(id);
+    mMaterialTexturesSet[asset] = false;
+}
 
+LLTerrainMaterials::Type LLTerrainMaterials::getMaterialType()
+{
+	LL_PROFILE_ZONE_SCOPED;
+
+    const BOOL use_textures = texturesReady() || !materialsReady();
+    return use_textures ? Type::TEXTURE : Type::PBR;
+}
+
+BOOL LLTerrainMaterials::texturesReady(BOOL boost)
+{
+    BOOL ready = TRUE;
+	for (S32 i = 0; i < ASSET_COUNT; i++)
+	{
+        if (!textureReady(mDetailTextures[i], boost))
+        {
+            ready = FALSE;
+        }
+	}
+    return ready;
+}
+
+BOOL LLTerrainMaterials::materialsReady(BOOL boost)
+{
+    BOOL ready = TRUE;
+	for (S32 i = 0; i < ASSET_COUNT; i++)
+	{
+        if (!materialReady(mDetailMaterials[i], mMaterialTexturesSet[i], boost))
+        {
+            ready = FALSE;
+        }
+    }
+    return ready;
+}
+
+// Boost the texture loading priority
+// Return true when ready to use (i.e. texture is sufficiently loaded)
+// static
+BOOL LLTerrainMaterials::textureReady(LLPointer<LLViewerFetchedTexture>& tex, BOOL boost)
+{
+    llassert(tex.notNull());
+
+    if (tex->getDiscardLevel() < 0)
+    {
+        if (boost)
+        {
+            tex->setBoostLevel(LLGLTexture::BOOST_TERRAIN); // in case we are at low detail
+            tex->addTextureStats(BASE_SIZE*BASE_SIZE);
+        }
+        return FALSE;
+    }
+    if ((tex->getDiscardLevel() != 0 &&
+         (tex->getWidth() < BASE_SIZE ||
+          tex->getHeight() < BASE_SIZE)))
+    {
+        if (boost)
+        {
+            S32 width = tex->getFullWidth();
+            S32 height = tex->getFullHeight();
+            S32 min_dim = llmin(width, height);
+            S32 ddiscard = 0;
+            while (min_dim > BASE_SIZE && ddiscard < MAX_DISCARD_LEVEL)
+            {
+                ddiscard++;
+                min_dim /= 2;
+            }
+            tex->setBoostLevel(LLGLTexture::BOOST_TERRAIN); // in case we are at low detail
+            tex->setMinDiscardLevel(ddiscard);
+            tex->addTextureStats(BASE_SIZE*BASE_SIZE); // priority
+        }
+        return FALSE;
+    }
+    if (tex->getComponents() == 0)
+    {
+        return FALSE;
+    }
+    return TRUE;
+}
+
+// Boost the loading priority of every known texture in the material
+// Return true when ready to use (i.e. material and all textures within are sufficiently loaded)
+// static
+BOOL LLTerrainMaterials::materialReady(LLPointer<LLFetchedGLTFMaterial>& mat, bool& textures_set, BOOL boost)
+{
+    if (!mat || !mat->isLoaded())
+    {
+        return FALSE;
+    }
+
+    // Material is loaded, but textures may not be
+    if (!textures_set)
+    {
+        // *NOTE: These can sometimes be set to to nullptr due to
+        // updateTEMaterialTextures. For the sake of robustness, we emulate
+        // that fetching behavior by setting textures of null IDs to nullptr.
+        mat->mBaseColorTexture = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_BASE_COLOR]);
+        mat->mNormalTexture = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_NORMAL]);
+        mat->mMetallicRoughnessTexture = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_METALLIC_ROUGHNESS]);
+        mat->mEmissiveTexture = fetch_terrain_texture(mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_EMISSIVE]);
+        textures_set = true;
+
+        return FALSE;
+    }
+
+    if (mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_BASE_COLOR].notNull() && !textureReady(mat->mBaseColorTexture, boost))
+    {
+        return FALSE;
+    }
+    if (mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_NORMAL].notNull() && !textureReady(mat->mNormalTexture, boost))
+    {
+        return FALSE;
+    }
+    if (mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_METALLIC_ROUGHNESS].notNull() && !textureReady(mat->mMetallicRoughnessTexture, boost))
+    {
+        return FALSE;
+    }
+    if (mat->mTextureId[LLGLTFMaterial::GLTF_TEXTURE_INFO_EMISSIVE].notNull() && !textureReady(mat->mEmissiveTexture, boost))
+    {
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
+
+LLVLComposition::LLVLComposition(LLSurface *surfacep, const U32 width, const F32 scale) :
+    LLTerrainMaterials(),
+	LLViewerLayer(width, scale)
+{
 	// Load Terrain Textures - Original ones
-	setDetailTextureID(0, TERRAIN_DIRT_DETAIL);
-	setDetailTextureID(1, TERRAIN_GRASS_DETAIL);
-	setDetailTextureID(2, TERRAIN_MOUNTAIN_DETAIL);
-	setDetailTextureID(3, TERRAIN_ROCK_DETAIL);
+	setDetailAssetID(0, TERRAIN_DIRT_DETAIL);
+	setDetailAssetID(1, TERRAIN_GRASS_DETAIL);
+	setDetailAssetID(2, TERRAIN_MOUNTAIN_DETAIL);
+	setDetailAssetID(3, TERRAIN_ROCK_DETAIL);
+
+	mSurfacep = surfacep;
 
 	// Initialize the texture matrix to defaults.
 	for (S32 i = 0; i < CORNER_COUNT; ++i)
@@ -76,14 +261,12 @@ LLVLComposition::LLVLComposition(LLSurface *surfacep, const U32 width, const F32
 		mStartHeight[i] = gSavedSettings.getF32("TerrainColorStartHeight");
 		mHeightRange[i] = gSavedSettings.getF32("TerrainColorHeightRange");
 	}
-	mTexScaleX = 16.f;
-	mTexScaleY = 16.f;
-	mTexturesLoaded = FALSE;
 }
 
 
 LLVLComposition::~LLVLComposition()
 {
+    LLTerrainMaterials::~LLTerrainMaterials();
 }
 
 
@@ -92,20 +275,6 @@ void LLVLComposition::setSurface(LLSurface *surfacep)
 	mSurfacep = surfacep;
 }
 
-
-void LLVLComposition::setDetailTextureID(S32 corner, const LLUUID& id)
-{
-	if(id.isNull())
-	{
-		return;
-	}
-	// This is terrain texture, but we are not setting it as BOOST_TERRAIN
-	// since we will be manipulating it later as needed.
-	mDetailTextures[corner] = LLViewerTextureManager::getFetchedTexture(id);
-	mDetailTextures[corner]->setNoDelete() ;
-	mRawImages[corner] = NULL;
-}
-
 BOOL LLVLComposition::generateHeights(const F32 x, const F32 y,
 									  const F32 width, const F32 height)
 {
@@ -149,10 +318,6 @@ BOOL LLVLComposition::generateHeights(const F32 x, const F32 y,
 	const F32 noise_magnitude = 2.f;		//  Degree to which noise modulates composition layer (versus
 											//  simple height)
 
-	// Heights map into textures as 0-1 = first, 1-2 = second, etc.
-	// So we need to compress heights into this range.
-	const S32 NUM_TEXTURES = 4;
-
 	const F32 xyScaleInv = (1.f / xyScale);
 	const F32 zScaleInv = (1.f / zScale);
 
@@ -199,7 +364,7 @@ BOOL LLVLComposition::generateHeights(const F32 x, const F32 y,
 			twiddle += turbulence2(vec, 2)*slope_squared;	//  High frequency component
 			twiddle *= noise_magnitude;
 
-			F32 scaled_noisy_height = (height + twiddle - start_height) * F32(NUM_TEXTURES) / height_range;
+			F32 scaled_noisy_height = (height + twiddle - start_height) * F32(ASSET_COUNT) / height_range;
 
 			scaled_noisy_height = llmax(0.f, scaled_noisy_height);
 			scaled_noisy_height = llmin(3.f, scaled_noisy_height);
@@ -209,49 +374,20 @@ BOOL LLVLComposition::generateHeights(const F32 x, const F32 y,
 	return TRUE;
 }
 
-static const U32 BASE_SIZE = 128;
+LLTerrainMaterials gLocalTerrainMaterials;
 
 BOOL LLVLComposition::generateComposition()
 {
-
 	if (!mParamsReady)
 	{
 		// All the parameters haven't been set yet (we haven't gotten the message from the sim)
 		return FALSE;
 	}
 
-	for (S32 i = 0; i < 4; i++)
-	{
-		if (mDetailTextures[i]->getDiscardLevel() < 0)
-		{
-			mDetailTextures[i]->setBoostLevel(LLGLTexture::BOOST_TERRAIN); // in case we are at low detail
-			mDetailTextures[i]->addTextureStats(BASE_SIZE*BASE_SIZE);
-			return FALSE;
-		}
-		if ((mDetailTextures[i]->getDiscardLevel() != 0 &&
-			 (mDetailTextures[i]->getWidth() < BASE_SIZE ||
-			  mDetailTextures[i]->getHeight() < BASE_SIZE)))
-		{
-			S32 width = mDetailTextures[i]->getFullWidth();
-			S32 height = mDetailTextures[i]->getFullHeight();
-			S32 min_dim = llmin(width, height);
-			S32 ddiscard = 0;
-			while (min_dim > BASE_SIZE && ddiscard < MAX_DISCARD_LEVEL)
-			{
-				ddiscard++;
-				min_dim /= 2;
-			}
-			mDetailTextures[i]->setBoostLevel(LLGLTexture::BOOST_TERRAIN); // in case we are at low detail
-			mDetailTextures[i]->setMinDiscardLevel(ddiscard);
-			mDetailTextures[i]->addTextureStats(BASE_SIZE*BASE_SIZE); // priority
-			return FALSE;
-		}
-	}
-	
-	return TRUE;
+    return LLTerrainMaterials::generateMaterials();
 }
 
-BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
+BOOL LLVLComposition::generateMinimapTileLand(const F32 x, const F32 y,
 									  const F32 width, const F32 height)
 {
 	LL_PROFILE_ZONE_SCOPED
@@ -259,8 +395,6 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 	llassert(x >= 0.f);
 	llassert(y >= 0.f);
 
-	LLTimer gen_timer;
-
 	///////////////////////////
 	//
 	// Generate raw data arrays for surface textures
@@ -268,15 +402,61 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 	//
 
 	// These have already been validated by generateComposition.
-	U8* st_data[4];
-	S32 st_data_size[4]; // for debugging
-
-	for (S32 i = 0; i < 4; i++)
+	U8* st_data[ASSET_COUNT];
+	S32 st_data_size[ASSET_COUNT]; // for debugging
+
+    const bool use_textures = getMaterialType() != LLTerrainMaterials::Type::PBR;
+    // *TODO: Remove this as it is reduandant computation (first and foremost
+    // because getMaterialType() does something similar, but also... shouldn't
+    // the textures/materials already be loaded by now?)
+    if (use_textures)
+    {
+        if (!texturesReady()) { return FALSE; }
+    }
+    else
+    {
+        if (!materialsReady()) { return FALSE; }
+    }
+
+	for (S32 i = 0; i < ASSET_COUNT; i++)
 	{
 		if (mRawImages[i].isNull())
 		{
 			// Read back a raw image for this discard level, if it exists
-			S32 min_dim = llmin(mDetailTextures[i]->getFullWidth(), mDetailTextures[i]->getFullHeight());
+            LLViewerFetchedTexture* tex;
+            LLViewerFetchedTexture* tex_emissive; // Can be null
+            bool has_base_color_factor;
+            bool has_emissive_factor;
+            LLColor3 base_color_factor;
+            LLColor3 emissive_factor;
+            if (use_textures)
+            {
+                tex = mDetailTextures[i];
+                tex_emissive = nullptr;
+                has_base_color_factor = false;
+                has_emissive_factor = false;
+                llassert(tex);
+            }
+            else
+            {
+                tex = mDetailMaterials[i]->mBaseColorTexture;
+                tex_emissive = mDetailMaterials[i]->mEmissiveTexture;
+                base_color_factor = LLColor3(mDetailMaterials[i]->mBaseColor);
+                // *HACK: Treat alpha as black
+                base_color_factor *= (mDetailMaterials[i]->mBaseColor.mV[VW]);
+                emissive_factor = mDetailMaterials[i]->mEmissiveColor;
+                has_base_color_factor = (base_color_factor.mV[VX] != 1.f ||
+                                         base_color_factor.mV[VY] != 1.f ||
+                                         base_color_factor.mV[VZ] != 1.f);
+                has_emissive_factor = (emissive_factor.mV[VX] != 1.f ||
+                                       emissive_factor.mV[VY] != 1.f ||
+                                       emissive_factor.mV[VZ] != 1.f);
+            }
+
+            if (!tex) { tex = LLViewerFetchedTexture::sWhiteImagep; }
+            // tex_emissive can be null, and then will be ignored
+
+			S32 min_dim = llmin(tex->getFullWidth(), tex->getFullHeight());
 			S32 ddiscard = 0;
 			while (min_dim > BASE_SIZE && ddiscard < MAX_DISCARD_LEVEL)
 			{
@@ -284,34 +464,92 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 				min_dim /= 2;
 			}
 
-			BOOL delete_raw = (mDetailTextures[i]->reloadRawImage(ddiscard) != NULL) ;
-			if(mDetailTextures[i]->getRawImageLevel() != ddiscard)//raw iamge is not ready, will enter here again later.
+			BOOL delete_raw = (tex->reloadRawImage(ddiscard) != NULL) ;
+			if(tex->getRawImageLevel() != ddiscard)
 			{
-                if (mDetailTextures[i]->getFetchPriority() <= 0.0f && !mDetailTextures[i]->hasSavedRawImage())
+                // Raw image is not ready, will enter here again later.
+                if (tex->getFetchPriority() <= 0.0f && !tex->hasSavedRawImage())
                 {
-                    mDetailTextures[i]->setBoostLevel(LLGLTexture::BOOST_MAP);
-                    mDetailTextures[i]->forceToRefetchTexture(ddiscard);
+                    tex->setBoostLevel(LLGLTexture::BOOST_MAP);
+                    tex->forceToRefetchTexture(ddiscard);
                 }
 
 				if(delete_raw)
 				{
-					mDetailTextures[i]->destroyRawImage() ;
+					tex->destroyRawImage() ;
 				}
-				LL_DEBUGS("Terrain") << "cached raw data for terrain detail texture is not ready yet: " << mDetailTextures[i]->getID() << " Discard: " << ddiscard << LL_ENDL;
 				return FALSE;
 			}
+            if (tex_emissive)
+            {
+                if(tex_emissive->getRawImageLevel() != ddiscard)
+                {
+                    // Raw image is not ready, will enter here again later.
+                    if (tex_emissive->getFetchPriority() <= 0.0f && !tex_emissive->hasSavedRawImage())
+                    {
+                        tex_emissive->setBoostLevel(LLGLTexture::BOOST_MAP);
+                        tex_emissive->forceToRefetchTexture(ddiscard);
+                    }
+
+                    if(delete_raw)
+                    {
+                        tex_emissive->destroyRawImage() ;
+                    }
+                    return FALSE;
+                }
+            }
 
-			mRawImages[i] = mDetailTextures[i]->getRawImage() ;
+			mRawImages[i] = tex->getRawImage() ;
 			if(delete_raw)
 			{
-				mDetailTextures[i]->destroyRawImage() ;
+				tex->destroyRawImage() ;
 			}
-			if (mDetailTextures[i]->getWidth(ddiscard) != BASE_SIZE ||
-				mDetailTextures[i]->getHeight(ddiscard) != BASE_SIZE ||
-				mDetailTextures[i]->getComponents() != 3)
+
+            // *TODO: This isn't quite right for PBR:
+            // 1) It does not convert the color images from SRGB to linear
+            // before mixing (which will always require copying the image).
+            // 2) It mixes emissive and base color before mixing terrain
+            // materials, but it should be the other way around
+            // 3) The composite function used to put emissive into base color
+            // is not an alpha blend.
+            // Long-term, we should consider a method that is more
+            // maintainable. Shaders, perhaps? Bake shaders to textures?
+            LLPointer<LLImageRaw> raw_emissive;
+            if (tex_emissive)
+            {
+                raw_emissive = tex_emissive->getRawImage();
+                if (has_emissive_factor ||
+                    tex_emissive->getWidth(ddiscard) != BASE_SIZE ||
+                    tex_emissive->getHeight(ddiscard) != BASE_SIZE ||
+                    tex_emissive->getComponents() != 4)
+                {
+                    LLPointer<LLImageRaw> newraw_emissive = new LLImageRaw(BASE_SIZE, BASE_SIZE, 4);
+                    // Copy RGB, leave alpha alone (set to opaque by default)
+                    newraw_emissive->copy(mRawImages[i]);
+                    if (has_emissive_factor)
+                    {
+                        newraw_emissive->tint(emissive_factor);
+                    }
+                    raw_emissive = newraw_emissive; // deletes old
+                }
+            }
+			if (has_base_color_factor ||
+                raw_emissive ||
+                tex->getWidth(ddiscard) != BASE_SIZE ||
+				tex->getHeight(ddiscard) != BASE_SIZE ||
+				tex->getComponents() != 3)
 			{
 				LLPointer<LLImageRaw> newraw = new LLImageRaw(BASE_SIZE, BASE_SIZE, 3);
 				newraw->composite(mRawImages[i]);
+                if (has_base_color_factor)
+                {
+                    newraw->tint(base_color_factor);
+                }
+                // Apply emissive texture
+                if (raw_emissive)
+                {
+                    newraw->composite(raw_emissive);
+                }
 				mRawImages[i] = newraw; // deletes old
 			}
 		}
@@ -333,12 +571,12 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 
 	if (x_end > mWidth)
 	{
-		LL_WARNS("Terrain") << "x end > width" << LL_ENDL;
+        llassert(false);
 		x_end = mWidth;
 	}
 	if (y_end > mWidth)
 	{
-		LL_WARNS("Terrain") << "y end > width" << LL_ENDL;
+        llassert(false);
 		y_end = mWidth;
 	}
 
@@ -368,7 +606,7 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 	
 	if (tex_comps != st_comps)
 	{
-		LL_WARNS("Terrain") << "Base texture comps != input texture comps" << LL_ENDL;
+        llassert(false);
 		return FALSE;
 	}
 
@@ -459,7 +697,7 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 	}
 	texturep->setSubImage(raw, tex_x_begin, tex_y_begin, tex_x_end - tex_x_begin, tex_y_end - tex_y_begin);
 
-	for (S32 i = 0; i < 4; i++)
+	for (S32 i = 0; i < ASSET_COUNT; i++)
 	{
 		// Un-boost detatil textures (will get re-boosted if rendering in high detail)
 		mDetailTextures[i]->setBoostLevel(LLGLTexture::BOOST_NONE);
@@ -469,19 +707,19 @@ BOOL LLVLComposition::generateTexture(const F32 x, const F32 y,
 	return TRUE;
 }
 
-LLUUID LLVLComposition::getDetailTextureID(S32 corner)
-{
-	return mDetailTextures[corner]->getID();
-}
-
-LLViewerFetchedTexture* LLVLComposition::getDetailTexture(S32 corner)
+F32 LLVLComposition::getStartHeight(S32 corner)
 {
-	return mDetailTextures[corner];
+	return mStartHeight[corner];
 }
 
-F32 LLVLComposition::getStartHeight(S32 corner)
+void LLVLComposition::setDetailAssetID(S32 asset, const LLUUID& id)
 {
-	return mStartHeight[corner];
+	if (id.isNull())
+	{
+        return;
+    }
+    LLTerrainMaterials::setDetailAssetID(asset, id);
+	mRawImages[asset] = NULL;
 }
 
 void LLVLComposition::setStartHeight(S32 corner, const F32 start_height)
diff --git a/indra/newview/llvlcomposition.h b/indra/newview/llvlcomposition.h
index 2dd04ac5a5..d59c0f95bb 100644
--- a/indra/newview/llvlcomposition.h
+++ b/indra/newview/llvlcomposition.h
@@ -28,11 +28,54 @@
 #define LL_LLVLCOMPOSITION_H
 
 #include "llviewerlayer.h"
-#include "llviewertexture.h"
+#include "llpointer.h"
+
+#include "llimage.h"
 
 class LLSurface;
 
-class LLVLComposition : public LLViewerLayer
+class LLViewerFetchedTexture;
+class LLFetchedGLTFMaterial;
+
+class LLTerrainMaterials
+{
+public:
+	friend class LLDrawPoolTerrain;
+
+    LLTerrainMaterials();
+    virtual ~LLTerrainMaterials();
+
+	// Heights map into textures (or materials) as 0-1 = first, 1-2 = second, etc.
+	// So we need to compress heights into this range.
+    static const S32 ASSET_COUNT = 4;
+
+    enum class Type
+    {
+        TEXTURE,
+        PBR,
+        COUNT
+    };
+
+    BOOL generateMaterials();
+
+	LLUUID getDetailAssetID(S32 asset);
+	virtual void setDetailAssetID(S32 asset, const LLUUID& id);
+    Type getMaterialType();
+    BOOL texturesReady(BOOL boost = FALSE);
+    BOOL materialsReady(BOOL boost = FALSE);
+
+protected:
+    static BOOL textureReady(LLPointer<LLViewerFetchedTexture>& tex, BOOL boost = FALSE);
+    static BOOL materialReady(LLPointer<LLFetchedGLTFMaterial>& mat, bool& textures_set, BOOL boost = FALSE);
+	LLPointer<LLViewerFetchedTexture> mDetailTextures[ASSET_COUNT];
+	LLPointer<LLFetchedGLTFMaterial> mDetailMaterials[ASSET_COUNT];
+    bool mMaterialTexturesSet[ASSET_COUNT];
+};
+
+// Local materials to override all regions
+extern LLTerrainMaterials gLocalTerrainMaterials;
+
+class LLVLComposition : public LLTerrainMaterials, public LLViewerLayer
 {
 public:
 	LLVLComposition(LLSurface *surfacep, const U32 width, const F32 scale);
@@ -44,7 +87,11 @@ public:
 	BOOL generateHeights(const F32 x, const F32 y, const F32 width, const F32 height);
 	BOOL generateComposition();
 	// Generate texture from composition values.
-	BOOL generateTexture(const F32 x, const F32 y, const F32 width, const F32 height);		
+	BOOL generateMinimapTileLand(const F32 x, const F32 y, const F32 width, const F32 height);		
+
+	// Heights map into textures (or materials) as 0-1 = first, 1-2 = second, etc.
+	// So we need to compress heights into this range.
+    static const S32 ASSET_COUNT = 4;
 
 	// Use these as indeces ito the get/setters below that use 'corner'
 	enum ECorner
@@ -55,12 +102,11 @@ public:
 		NORTHEAST = 3,
 		CORNER_COUNT = 4
 	};
-	LLUUID getDetailTextureID(S32 corner);
-	LLViewerFetchedTexture* getDetailTexture(S32 corner);
+
+	void setDetailAssetID(S32 asset, const LLUUID& id) override;
 	F32 getStartHeight(S32 corner);
 	F32 getHeightRange(S32 corner);
 
-	void setDetailTextureID(S32 corner, const LLUUID& id);
 	void setStartHeight(S32 corner, F32 start_height);
 	void setHeightRange(S32 corner, F32 range);
 
@@ -68,19 +114,21 @@ public:
 	friend class LLDrawPoolTerrain;
 	void setParamsReady()		{ mParamsReady = TRUE; }
 	BOOL getParamsReady() const	{ return mParamsReady; }
+
 protected:
-	BOOL mParamsReady;
+    static BOOL textureReady(LLPointer<LLViewerFetchedTexture>& tex, BOOL boost = FALSE);
+    static BOOL materialReady(LLPointer<LLFetchedGLTFMaterial>& mat, bool& textures_set, BOOL boost = FALSE);
+
+	BOOL mParamsReady = FALSE;
 	LLSurface *mSurfacep;
-	BOOL mTexturesLoaded;
 
-	LLPointer<LLViewerFetchedTexture> mDetailTextures[CORNER_COUNT];
-	LLPointer<LLImageRaw> mRawImages[CORNER_COUNT];
+	LLPointer<LLImageRaw> mRawImages[LLTerrainMaterials::ASSET_COUNT];
 
 	F32 mStartHeight[CORNER_COUNT];
 	F32 mHeightRange[CORNER_COUNT];
 
-	F32 mTexScaleX;
-	F32 mTexScaleY;
+	F32 mTexScaleX = 16.f;
+	F32 mTexScaleY = 16.f;
 };
 
 #endif //LL_LLVLCOMPOSITION_H
diff --git a/indra/newview/llvosurfacepatch.cpp b/indra/newview/llvosurfacepatch.cpp
index 15fabf0414..9544450a69 100644
--- a/indra/newview/llvosurfacepatch.cpp
+++ b/indra/newview/llvosurfacepatch.cpp
@@ -39,6 +39,7 @@
 #include "llviewerobjectlist.h"
 #include "llviewerregion.h"
 #include "llvlcomposition.h"
+#include "llvolume.h"
 #include "llvovolume.h"
 #include "pipeline.h"
 #include "llspatialpartition.h"
@@ -241,48 +242,50 @@ BOOL LLVOSurfacePatch::updateLOD()
 	return TRUE;
 }
 
-void LLVOSurfacePatch::getGeometry(LLStrider<LLVector3> &verticesp,
-								LLStrider<LLVector3> &normalsp,
-								LLStrider<LLVector2> &texCoords0p,
-								LLStrider<LLVector2> &texCoords1p,
-								LLStrider<U16> &indicesp)
+void LLVOSurfacePatch::getTerrainGeometry(LLStrider<LLVector3> &verticesp,
+                                              LLStrider<LLVector3> &normalsp,
+                                              LLStrider<LLVector2> &texCoords0p,
+                                              LLStrider<LLVector2> &texCoords1p,
+                                              LLStrider<U16> &indicesp)
 {
 	LLFace* facep = mDrawable->getFace(0);
-	if (facep)
-	{
-		U32 index_offset = facep->getGeomIndex();
-
-		updateMainGeometry(facep, 
-						verticesp,
-						normalsp,
-						texCoords0p,
-						texCoords1p,
-						indicesp,
-						index_offset);
-		updateNorthGeometry(facep, 
-							verticesp,
-							normalsp,
-							texCoords0p,
-							texCoords1p,
-							indicesp,
-							index_offset);
-		updateEastGeometry(facep, 
-							verticesp,
-							normalsp,
-							texCoords0p,
-							texCoords1p,
-							indicesp,
-							index_offset);
-	}
+    if (!facep)
+    {
+        return;
+    }
+
+    U32 index_offset = facep->getGeomIndex();
+
+    updateMainGeometry(facep, 
+                    verticesp,
+                    normalsp,
+                    texCoords0p,
+                    texCoords1p,
+                    indicesp,
+                    index_offset);
+    updateNorthGeometry(facep, 
+                        verticesp,
+                        normalsp,
+                        texCoords0p,
+                        texCoords1p,
+                        indicesp,
+                        index_offset);
+    updateEastGeometry(facep, 
+                        verticesp,
+                        normalsp,
+                        texCoords0p,
+                        texCoords1p,
+                        indicesp,
+                        index_offset);
 }
 
 void LLVOSurfacePatch::updateMainGeometry(LLFace *facep,
-										LLStrider<LLVector3> &verticesp,
-										LLStrider<LLVector3> &normalsp,
-										LLStrider<LLVector2> &texCoords0p,
-										LLStrider<LLVector2> &texCoords1p,
-										LLStrider<U16> &indicesp,
-										U32 &index_offset)
+                                        LLStrider<LLVector3> &verticesp,
+                                        LLStrider<LLVector3> &normalsp,
+                                        LLStrider<LLVector2> &texCoords0p,
+                                        LLStrider<LLVector2> &texCoords1p,
+                                        LLStrider<U16> &indicesp,
+                                        U32 &index_offset)
 {
 	S32 i, j, x, y;
 
@@ -381,12 +384,12 @@ void LLVOSurfacePatch::updateMainGeometry(LLFace *facep,
 
 
 void LLVOSurfacePatch::updateNorthGeometry(LLFace *facep,
-										LLStrider<LLVector3> &verticesp,
-										LLStrider<LLVector3> &normalsp,
-										LLStrider<LLVector2> &texCoords0p,
-										LLStrider<LLVector2> &texCoords1p,
-										LLStrider<U16> &indicesp,
-										U32 &index_offset)
+                                        LLStrider<LLVector3> &verticesp,
+                                        LLStrider<LLVector3> &normalsp,
+                                        LLStrider<LLVector2> &texCoords0p,
+                                        LLStrider<LLVector2> &texCoords1p,
+                                        LLStrider<U16> &indicesp,
+                                        U32 &index_offset)
 {
 	S32 i, x, y;
 
@@ -571,12 +574,12 @@ void LLVOSurfacePatch::updateNorthGeometry(LLFace *facep,
 }
 
 void LLVOSurfacePatch::updateEastGeometry(LLFace *facep,
-										  LLStrider<LLVector3> &verticesp,
-										  LLStrider<LLVector3> &normalsp,
-										  LLStrider<LLVector2> &texCoords0p,
-										  LLStrider<LLVector2> &texCoords1p,
-										  LLStrider<U16> &indicesp,
-										  U32 &index_offset)
+                                          LLStrider<LLVector3> &verticesp,
+                                          LLStrider<LLVector3> &normalsp,
+                                          LLStrider<LLVector2> &texCoords0p,
+                                          LLStrider<LLVector2> &texCoords1p,
+                                          LLStrider<U16> &indicesp,
+                                          U32 &index_offset)
 {
 	S32 i, x, y;
 
@@ -982,6 +985,49 @@ LLTerrainPartition::LLTerrainPartition(LLViewerRegion* regionp)
 	mPartitionType = LLViewerRegion::PARTITION_TERRAIN;
 }
 
+// Do not add vertices; honor strict vertex count specified by strider_vertex_count
+void gen_terrain_tangents(U16                    strider_vertex_count,
+                          U32                    strider_index_count,
+                          LLStrider<LLVector3>  &verticesp,
+                          LLStrider<LLVector3>  &normalsp,
+                          LLStrider<LLVector4a> &tangentsp,
+                          LLStrider<LLVector2>  &texCoords0p,
+                          LLStrider<U16>        &indicesp)
+{
+    LL_PROFILE_ZONE_SCOPED
+
+    LLVector4a            *vertices = new LLVector4a[strider_vertex_count];
+    LLVector4a            *normals  = new LLVector4a[strider_vertex_count];
+    LLVector4a            *tangents = new LLVector4a[strider_vertex_count];
+    std::vector<LLVector2> texcoords(strider_vertex_count);
+    std::vector<U16>       indices(strider_index_count);
+
+    for (U16 v = 0; v < strider_vertex_count; ++v)
+    {
+        F32 *vert    = verticesp[v].mV;
+        vertices[v]  = LLVector4a(vert[0], vert[1], vert[2], 1.f);
+        F32 *n       = normalsp[v].mV;
+        normals[v]   = LLVector4a(n[0], n[1], n[2], 1.f);
+        tangents[v]  = tangentsp[v];
+        texcoords[v] = texCoords0p[v];
+    }
+    for (U32 i = 0; i < strider_index_count; ++i)
+    {
+        indices[i] = indicesp[i];
+    }
+
+    LLCalculateTangentArray(strider_vertex_count, vertices, normals, texcoords.data(), strider_index_count / 3, indices.data(), tangents);
+
+    for (U16 v = 0; v < strider_vertex_count; ++v)
+    {
+        tangentsp[v] = tangents[v];
+    }
+
+    delete[] vertices;
+    delete[] normals;
+    delete[] tangents;
+}
+
 void LLTerrainPartition::getGeometry(LLSpatialGroup* group)
 {
     LL_PROFILE_ZONE_SCOPED;
@@ -989,35 +1035,57 @@ void LLTerrainPartition::getGeometry(LLSpatialGroup* group)
 	LLVertexBuffer* buffer = group->mVertexBuffer;
 
 	//get vertex buffer striders
-	LLStrider<LLVector3> vertices;
-	LLStrider<LLVector3> normals;
-	LLStrider<LLVector2> texcoords2;
-	LLStrider<LLVector2> texcoords;
-	LLStrider<U16> indices;
-
-	llassert_always(buffer->getVertexStrider(vertices));
-	llassert_always(buffer->getNormalStrider(normals));
-	llassert_always(buffer->getTexCoord0Strider(texcoords));
-	llassert_always(buffer->getTexCoord1Strider(texcoords2));
-	llassert_always(buffer->getIndexStrider(indices));
-
-	U32 indices_index = 0;
-	U32 index_offset = 0;
-
-	for (std::vector<LLFace*>::iterator i = mFaceList.begin(); i != mFaceList.end(); ++i)
-	{
-		LLFace* facep = *i;
-
-		facep->setIndicesIndex(indices_index);
-		facep->setGeomIndex(index_offset);
-		facep->setVertexBuffer(buffer);
-
-		LLVOSurfacePatch* patchp = (LLVOSurfacePatch*) facep->getViewerObject();
-		patchp->getGeometry(vertices, normals, texcoords, texcoords2, indices);
-
-		indices_index += facep->getIndicesCount();
-		index_offset += facep->getGeomCount();
-	}
+	LLStrider<LLVector3> vertices_start;
+	LLStrider<LLVector3> normals_start;
+	LLStrider<LLVector4a> tangents_start;
+	LLStrider<LLVector2> texcoords_start;
+	LLStrider<LLVector2> texcoords2_start;
+	LLStrider<U16> indices_start;
+
+	llassert_always(buffer->getVertexStrider(vertices_start));
+	llassert_always(buffer->getNormalStrider(normals_start));
+	llassert_always(buffer->getTangentStrider(tangents_start));
+	llassert_always(buffer->getTexCoord0Strider(texcoords_start));
+	llassert_always(buffer->getTexCoord1Strider(texcoords2_start));
+	llassert_always(buffer->getIndexStrider(indices_start));
+
+    U32 indices_index = 0;
+    U32 index_offset = 0;
+
+    {
+        LLStrider<LLVector3> vertices = vertices_start;
+        LLStrider<LLVector3> normals = normals_start;
+        LLStrider<LLVector2> texcoords = texcoords_start;
+        LLStrider<LLVector2> texcoords2 = texcoords2_start;
+        LLStrider<U16> indices = indices_start;
+
+        for (std::vector<LLFace*>::iterator i = mFaceList.begin(); i != mFaceList.end(); ++i)
+        {
+            LLFace* facep = *i;
+
+            facep->setIndicesIndex(indices_index);
+            facep->setGeomIndex(index_offset);
+            facep->setVertexBuffer(buffer);
+
+            LLVOSurfacePatch* patchp = (LLVOSurfacePatch*) facep->getViewerObject();
+            patchp->getTerrainGeometry(vertices, normals, texcoords, texcoords2, indices);
+
+            indices_index += facep->getIndicesCount();
+            index_offset += facep->getGeomCount();
+        }
+    }
+
+    const bool has_tangents = tangents_start.get() != nullptr;
+    if (has_tangents)
+    {
+        LLStrider<LLVector3> vertices = vertices_start;
+        LLStrider<LLVector3> normals = normals_start;
+        LLStrider<LLVector4a> tangents = tangents_start;
+        LLStrider<LLVector2> texcoords = texcoords_start;
+        LLStrider<U16> indices = indices_start;
+
+        gen_terrain_tangents(index_offset, indices_index, vertices, normals, tangents, texcoords, indices);
+    }
 
 	buffer->unmapBuffer();
 	mFaceList.clear();
diff --git a/indra/newview/llvosurfacepatch.h b/indra/newview/llvosurfacepatch.h
index aed67162d1..a3dcb945d1 100644
--- a/indra/newview/llvosurfacepatch.h
+++ b/indra/newview/llvosurfacepatch.h
@@ -63,11 +63,11 @@ public:
 	/*virtual*/ BOOL        updateGeometry(LLDrawable *drawable);
 	/*virtual*/ BOOL		updateLOD();
 	/*virtual*/ void		updateFaceSize(S32 idx);
-	void getGeometry(LLStrider<LLVector3> &verticesp,
-								LLStrider<LLVector3> &normalsp,
-								LLStrider<LLVector2> &texCoords0p,
-								LLStrider<LLVector2> &texCoords1p,
-								LLStrider<U16> &indicesp);
+    void getTerrainGeometry(LLStrider<LLVector3> &verticesp,
+                                LLStrider<LLVector3> &normalsp,
+                                LLStrider<LLVector2> &texCoords0p,
+                                LLStrider<LLVector2> &texCoords1p,
+                                LLStrider<U16> &indicesp);
 
 	/*virtual*/ void updateTextures();
 	/*virtual*/ void setPixelAreaAndAngle(LLAgent &agent); // generate accurate apparent angle and area
diff --git a/indra/newview/skins/default/xui/en/notifications.xml b/indra/newview/skins/default/xui/en/notifications.xml
index d642ea162c..df9f53686e 100644
--- a/indra/newview/skins/default/xui/en/notifications.xml
+++ b/indra/newview/skins/default/xui/en/notifications.xml
@@ -4004,7 +4004,7 @@ Are you sure you want to return objects owned by [USER_NAME]?
 Couldn&apos;t set region textures:
 Terrain texture [TEXTURE_NUM] has an invalid bit depth of [TEXTURE_BIT_DEPTH].
 
-Replace texture [TEXTURE_NUM] with a 24-bit [MAX_SIZE]x[MAX_SIZE] or smaller image then click &quot;Apply&quot; again.
+Replace texture [TEXTURE_NUM] with an RGB [MAX_SIZE]x[MAX_SIZE] or smaller image then click &quot;Apply&quot; again.
   <tag>fail</tag>
   </notification>
 
@@ -4015,7 +4015,7 @@ Replace texture [TEXTURE_NUM] with a 24-bit [MAX_SIZE]x[MAX_SIZE] or smaller ima
 Couldn&apos;t set region textures:
 Terrain texture [TEXTURE_NUM] is too large at [TEXTURE_SIZE_X]x[TEXTURE_SIZE_Y].
 
-Replace texture [TEXTURE_NUM] with a 24-bit [MAX_SIZE]x[MAX_SIZE] or smaller image then click &quot;Apply&quot; again.
+Replace texture [TEXTURE_NUM] with an RGB [MAX_SIZE]x[MAX_SIZE] or smaller image then click &quot;Apply&quot; again.
   </notification>
 
   <notification
diff --git a/indra/newview/skins/default/xui/en/panel_region_terrain.xml b/indra/newview/skins/default/xui/en/panel_region_terrain.xml
index 2aaea04a6d..88855ab739 100644
--- a/indra/newview/skins/default/xui/en/panel_region_terrain.xml
+++ b/indra/newview/skins/default/xui/en/panel_region_terrain.xml
@@ -76,29 +76,61 @@
      left="8"
      top="30"
      width="460" />
+    <combo_box
+     layout="topleft"
+     left="10"
+     top="105"
+     follows="left|top"
+     name="terrain_material_type"
+     width="170">
+        <combo_box.item
+         label="Terrain Textures"
+         name="Textures"
+         value="Textures" />
+        <combo_box.item
+         label="Terrain PBR Materials"
+         name="PBRMaterials"
+         value="PBRMaterials" />
+    </combo_box>
     <text
      type="string"
      length="1"
      follows="left|top"
+     halign="left"
+     valign="center"
      height="20"
      layout="topleft"
-     left="10"
      name="detail_texture_text"
-     top="110"
-     width="300">
-        Terrain Textures (requires 1024x1024, 24 bit .tga files)
+     top_delta="0"
+     left_delta="0"
+     width="170">
+        Terrain Textures
+    </text>
+    <text
+     type="string"
+     length="1"
+     halign="left"
+     valign="center"
+     follows="left|top"
+     height="20"
+     layout="topleft"
+     top_delta="0"
+     left_delta="180"
+     name="detail_texture_limits_text"
+     width="200">
+        Maximum size: 1024x1024
     </text>
     <texture_picker
      follows="left|top"
      height="100"
      layout="topleft"
-     left_delta="0"
+     left="10"
      name="texture_detail_0"
      default_image_id="0bc58228-74a0-7e83-89bc-5c23464bcec5"
-     top_delta="20"
+     top_delta="30"
      width="100" />
     <texture_picker
-     follows="left|top"
+     follows="top"
      height="100"
      layout="topleft"
      left_pad="10"
@@ -124,6 +156,50 @@
      default_image_id="53a2f406-4895-1d13-d541-d2e3b86bc19c"
      top_delta="0"
      width="100" />
+    <texture_picker
+     visible="false"
+     follows="left|top"
+     height="100"
+     layout="topleft"
+     left="10"
+     name="material_detail_0"
+     pick_type="material"
+     allow_no_texture="true"
+     top_delta="0"
+     width="100" />
+    <texture_picker
+     visible="false"
+     follows="left|top"
+     height="100"
+     layout="topleft"
+     left_pad="10"
+     name="material_detail_1"
+     pick_type="material"
+     allow_no_texture="true"
+     top_delta="0"
+     width="100" />
+    <texture_picker
+     visible="false"
+     follows="left|top"
+     height="100"
+     layout="topleft"
+     left_pad="10"
+     name="material_detail_2"
+     pick_type="material"
+     allow_no_texture="true"
+     top_delta="0"
+     width="100" />
+    <texture_picker
+     visible="false"
+     follows="left|top"
+     height="100"
+     layout="topleft"
+     left_pad="10"
+     name="material_detail_3"
+     pick_type="material"
+     allow_no_texture="true"
+     top_delta="0"
+     width="100" />
     <text
      type="string"
      length="1"