SL-17701: PBR: Add support for gltf Alpha MASK (cutoff)

3 files changed, 21 insertions, 3 deletions

diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbropaqueF.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbropaqueF.glsl
index b5c38bba04..b0becdbb5b 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/pbropaqueF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbropaqueF.glsl
@@ -76,17 +76,23 @@ VARYING vec2 vary_texcoord1;
     VARYING vec2 vary_texcoord2;
 #endif
 
+uniform float minimum_alpha; // PBR alphaMode: MASK, See: mAlphaCutoff, setAlphaCutoff()
+
 vec2 encode_normal(vec3 n);
 vec3 linear_to_srgb(vec3 c);
 
-const float M_PI = 3.141592653589793;
-
 void main()
 {
 // IF .mFeatures.mIndexedTextureChannels = LLGLSLShader::sIndexedTextureChannels;
 //    vec3 col = vertex_color.rgb * diffuseLookup(vary_texcoord0.xy).rgb;
 // else
-    vec3 col = vertex_color.rgb * texture2D(diffuseMap, vary_texcoord0.xy).rgb;
+    vec4 albedo = texture2D(diffuseMap, vary_texcoord0.xy).rgba;
+    if (albedo.a < minimum_alpha)
+    {
+        discard;
+    }
+
+    vec3 col = vertex_color.rgb * albedo.rgb;
 
 #ifdef HAS_NORMAL_MAP
     vec4 norm = texture2D(bumpMap, vary_texcoord1.xy);
diff --git a/indra/newview/lldrawpoolpbropaque.cpp b/indra/newview/lldrawpoolpbropaque.cpp
index 3930e11cf3..9fc3d51cad 100644
--- a/indra/newview/lldrawpoolpbropaque.cpp
+++ b/indra/newview/lldrawpoolpbropaque.cpp
@@ -95,6 +95,16 @@ void LLDrawPoolPBROpaque::renderDeferred(S32 pass)
         for (LLCullResult::drawinfo_iterator i = begin; i != end; ++i)
         {
             LLDrawInfo* pparams = *i;
+            LLGLTFMaterial *mat = pparams->mGLTFMaterial;
+
+            // glTF 2.0 Specification 3.9.4. Alpha Coverage
+            // mAlphaCutoff is only valid for LLGLTFMaterial::ALPHA_MODE_MASK
+            F32 min_alpha = -1.0;
+            if (mat->mAlphaMode == LLGLTFMaterial::ALPHA_MODE_MASK)
+            {
+                min_alpha = mat->mAlphaCutoff;
+            }
+            shader->uniform1f(LLShaderMgr::MINIMUM_ALPHA, min_alpha);
 
             if (pparams->mTexture.notNull())
             {
diff --git a/indra/newview/llmaterialeditor.cpp b/indra/newview/llmaterialeditor.cpp
index 5acf0600b6..6461aa71a6 100644
--- a/indra/newview/llmaterialeditor.cpp
+++ b/indra/newview/llmaterialeditor.cpp
@@ -1574,6 +1574,7 @@ void LLMaterialEditor::getGLTFMaterial(LLGLTFMaterial* mat)
 
     mat->mDoubleSided = getDoubleSided();
     mat->setAlphaMode(getAlphaMode());
+    mat->mAlphaCutoff = getAlphaCutoff();
 }
 
 void LLMaterialEditor::setFromGLTFMaterial(LLGLTFMaterial* mat)
@@ -1591,6 +1592,7 @@ void LLMaterialEditor::setFromGLTFMaterial(LLGLTFMaterial* mat)
 
     setDoubleSided(mat->mDoubleSided);
     setAlphaMode(mat->getAlphaMode());
+    setAlphaCutoff(mat->mAlphaCutoff);
 }
 
 void LLMaterialEditor::loadAsset()