1 files changed, 38 insertions, 1 deletions
diff --git a/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl b/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
index 636dfed4ba..bf5d106dab 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/textureUtilV.glsl
@@ -48,6 +48,7 @@ vec2 khr_texture_transform(vec2 texcoord, vec2 scale, float rotation, vec2 offse
     return (transform * vec3(texcoord, 1)).xy;
 }
 
+// A texture transform function for PBR materials applied to shape prims/Collada model prims
 // vertex_texcoord - The UV texture coordinates sampled from the vertex at
 //     runtime. Per SL convention, this is in a right-handed UV coordinate
 //     system. Collada models also have right-handed UVs.
@@ -65,7 +66,7 @@ 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
@@ -77,6 +78,19 @@ vec2 texture_transform(vec2 vertex_texcoord, vec4[2] khr_gltf_transform, mat4 sl
     return texcoord;
 }
 
+// Similar to texture_transform but no offset during coordinate system
+// conversion, and no texture animation support.
+vec2 terrain_texture_transform(vec2 vertex_texcoord, vec4[2] khr_gltf_transform)
+{
+    vec2 texcoord = vertex_texcoord;
+
+    texcoord.y = -texcoord.y;
+    texcoord = khr_texture_transform(texcoord, khr_gltf_transform[0].xy, khr_gltf_transform[0].z, khr_gltf_transform[1].xy);
+    texcoord.y = -texcoord.y;
+
+    return texcoord;
+}
+
 // Take the rotation only from both transforms and apply to the tangent. This
 // accounts for the change of the topology of the normal texture when a texture
 // rotation is applied to it.
@@ -120,3 +134,26 @@ vec3 tangent_space_transform(vec4 vertex_tangent, vec3 vertex_normal, vec4[2] kh
 
     return (weights.x * vertex_binormal.xyz) + (weights.y * vertex_tangent.xyz);
 }
+
+// Similar to tangent_space_transform but no offset during coordinate system
+// conversion, and no texture animation support.
+vec3 terrain_tangent_space_transform(vec4 vertex_tangent, vec3 vertex_normal, vec4[2] khr_gltf_transform)
+{
+    // Immediately convert to left-handed coordinate system ((0,1) -> (0, -1))
+    vec2 weights = vec2(0, -1);
+
+    // Apply KHR_texture_transform (rotation only)
+    float khr_rotation = khr_gltf_transform[0].z;
+    mat2 khr_rotation_mat = mat2(
+        cos(khr_rotation),-sin(khr_rotation),
+        sin(khr_rotation), cos(khr_rotation)
+    );
+    weights = khr_rotation_mat * weights;
+
+    // Convert back to right-handed coordinate system
+    weights.y = -weights.y;
+
+    vec3 vertex_binormal = vertex_tangent.w * cross(vertex_normal, vertex_tangent.xyz);
+
+    return (weights.x * vertex_binormal.xyz) + (weights.y * vertex_tangent.xyz);
+}