[hdSt] Fix Tangent vector calculation for MaterialX NormalMaps

Note that the difference in lighting in the baseline is due to differences in how UsdPreviewSurface and MaterialX's implementation of PreviewSurface handles roughness values for direct lights. Fixes #1585 (Internal change: 2306122)
PixarAnimationStudios · Nov 28, 2023 · c5d244e · c5d244e
1 parent bbd9ece
commit c5d244e
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Showing 22 changed files with 692 additions and 51 deletions.
diff --git a/pxr/imaging/hdSt/materialXShaderGen.cpp b/pxr/imaging/hdSt/materialXShaderGen.cpp
@@ -44,14 +44,22 @@ namespace mx = MaterialX;
 PXR_NAMESPACE_OPEN_SCOPE
 
 
-static const std::string MxHdTangentString = 
+static const std::string MxHdWorldSpaceVectors = 
 R"(
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_%s
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_%s());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
+#endif
+
 )";
 
 static const std::string MxHdLightString = 
@@ -147,6 +155,8 @@ HdStMaterialXShaderGen<Base>::_EmitGlslfxHeader(mx::ShaderStage& mxStage) const
     Base::emitLineBreak(mxStage);
     Base::emitComment("File Generated with HdStMaterialXShaderGen.", mxStage);
     Base::emitLineBreak(mxStage);
+    Base::emitString("#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx\n", mxStage);
+    Base::emitLineBreak(mxStage);
     Base::emitString(
         R"(-- configuration)" "\n"
         R"({)" "\n", mxStage);
@@ -198,7 +208,8 @@ HdStMaterialXShaderGen<Base>::_EmitGlslfxHeader(mx::ShaderStage& mxStage) const
         R"(    "techniques": {)" "\n"
         R"(        "default": {)" "\n"
         R"(            "surfaceShader": { )""\n"
-        R"(                "source": [ "MaterialX.Surface" ])""\n"
+        R"(                "source": [ "SurfaceHelpers.TangentSpace",)""\n"
+        R"(                            "MaterialX.Surface" ])""\n"
         R"(            })""\n"
         R"(        })""\n"
         R"(    })""\n"
@@ -356,6 +367,35 @@ HdStMaterialXShaderGen<Base>::_EmitMxSurfaceShader(
     Base::emitLineBreak(mxStage);
 }
 
+static std::string
+_GetTexcoordName(
+    mx::VariableBlock const& vertexDataBlock,
+    std::string const& defaultTexcoordName)
+{
+    // Texcoords could come from either a texcoord or a geomprop value node.
+    // We prioritize using the texcoord name over the geomprop. 
+
+    // Cycle through the vertexDataBlock to find the texcoord name.
+    std::string texcoordName = defaultTexcoordName;
+    for (size_t i = 0; i < vertexDataBlock.size(); ++i) {
+        const mx::ShaderPort* variable = vertexDataBlock[i];
+        const std::string mxVariableName = variable->getVariable();
+
+        // If we have a texcoord node, use the default texcoord name.
+        if (mxVariableName.compare(
+                0, mx::HW::T_TEXCOORD.size(), mx::HW::T_TEXCOORD) == 0) {
+            return defaultTexcoordName;
+        }
+        // Use the geomprop name if this is a vec2 geomprop value node 
+        if (mxVariableName.compare(
+                0, mx::HW::T_IN_GEOMPROP.size(), mx::HW::T_IN_GEOMPROP) == 0 &&
+            variable->getType() == mx::Type::VECTOR2) {
+            texcoordName = mxVariableName.substr(mx::HW::T_IN_GEOMPROP.size()+1);
+        }
+    }
+    return texcoordName;
+}
+
 template<typename Base>
 void 
 HdStMaterialXShaderGen<Base>::_EmitMxInitFunction(
@@ -372,8 +412,13 @@ HdStMaterialXShaderGen<Base>::_EmitMxInitFunction(
     emitLine("u_viewPosition = vec3(HdGet_worldToViewInverseMatrix()"
              " * vec4(0.0, 0.0, 0.0, 1.0))", mxStage);
 
-    // Calculate the worldspace tangent vector
-    Base::emitString(MxHdTangentString, mxStage);
+    // Calculate the worldspace position, normal and tangent vectors
+    const std::string texcoordName =
+        _GetTexcoordName(vertexData, _defaultTexcoordName);
+    Base::emitString(
+        TfStringPrintf(MxHdWorldSpaceVectors.c_str(), 
+            texcoordName.c_str(), texcoordName.c_str()), 
+        mxStage);
 
     // Add the vd declaration that translates HdVertexData -> MxVertexData
     std::string mxVertexDataName = "mx" + vertexData.getName();
@@ -501,21 +546,13 @@ HdStMaterialXShaderGen<Base>::_EmitMxVertexDataLine(
     // making sure to convert the Hd data (viewSpace) to Mx data (worldSpace)
     std::string hdVariableDef;
     const std::string mxVariableName = variable->getVariable();
-    if (mxVariableName.compare(mx::HW::T_POSITION_WORLD) == 0) {
 
-        // Convert to WorldSpace position
-        hdVariableDef = "vec3(HdGet_worldToViewInverseMatrix() * Peye)"
-                        + separator;
-    }
-    else if (mxVariableName.compare(mx::HW::T_NORMAL_WORLD) == 0) {
-
-        // Convert to WorldSpace normal (calculated in MxHdTangentString)
-        hdVariableDef = "normalWorld" + separator;
-    }
-    else if (mxVariableName.compare(mx::HW::T_TANGENT_WORLD) == 0) {
+    if (mxVariableName.compare(mx::HW::T_POSITION_WORLD) == 0 ||
+        mxVariableName.compare(mx::HW::T_NORMAL_WORLD) == 0 ||
+        mxVariableName.compare(mx::HW::T_TANGENT_WORLD) == 0) {
 
-        // Calculated in MxHdTangentString
-        hdVariableDef = "tangentWorld" + separator;
+        // Calculated in MxHdWorldSpaceVectors
+        hdVariableDef = mxVariableName.substr(1) + separator;
     }
     else if (mxVariableName.compare(mx::HW::T_POSITION_OBJECT) == 0) {
 

diff --git a/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SScopper.out b/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SScopper.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -10,7 +12,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -136,13 +139,21 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_st
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_st());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
-    vd = mxVertexData(normalWorld,tangentWorld,vec3(HdGet_worldToViewInverseMatrix() * Peye));
+#endif
+
+    vd = mxVertexData(normalWorld,tangentWorld,positionWorld);
 
     // Initialize Material Parameters
     base = HdGet_base();

diff --git a/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SSdefault.out b/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SSdefault.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -10,7 +12,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -136,13 +139,21 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_st
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_st());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
-    vd = mxVertexData(normalWorld,tangentWorld,vec3(HdGet_worldToViewInverseMatrix() * Peye));
+#endif
+
+    vd = mxVertexData(normalWorld,tangentWorld,positionWorld);
 
     // Initialize Material Parameters
     base = HdGet_base();

diff --git a/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SSmarble.out b/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SSmarble.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -10,7 +12,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -149,13 +152,21 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_st
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_st());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
-    vd = mxVertexData(normalWorld,tangentWorld,HdGet_points(),vec3(HdGet_worldToViewInverseMatrix() * Peye));
+#endif
+
+    vd = mxVertexData(normalWorld,tangentWorld,HdGet_points(),positionWorld);
 
     // Initialize Material Parameters
     base = HdGet_base();

diff --git a/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SStextured.out b/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SStextured.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -21,7 +23,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -167,19 +170,27 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_uv
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_uv());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
+#endif
+
     vd = mxVertexData(normalWorld,tangentWorld,
     #ifdef HD_HAS_uv
         HdGet_uv(),
     #else
         vec2(0.0),
     #endif
-        vec3(HdGet_worldToViewInverseMatrix() * Peye));
+        positionWorld);
 
     // Initialize Material Parameters
     base = HdGet_base();

diff --git a/...maging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SStextured_bindless.out b/...maging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_SStextured_bindless.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -21,7 +23,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -159,19 +162,27 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_uv
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_uv());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
+#endif
+
     vd = mxVertexData(normalWorld,tangentWorld,
     #ifdef HD_HAS_uv
         HdGet_uv(),
     #else
         vec2(0.0),
     #endif
-        vec3(HdGet_worldToViewInverseMatrix() * Peye));
+        positionWorld);
 
     // Initialize Material Parameters
     base = HdGet_base();

diff --git a/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_UsdPSdefault.out b/pxr/imaging/hdSt/testenv/testHdStMaterialXShaderGen/baseline/shadergen_UsdPSdefault.out
@@ -2,6 +2,8 @@
 
 // File Generated with HdStMaterialXShaderGen.
 
+#import $TOOLS/hdSt/shaders/surfaceHelpers.glslfx
+
 -- configuration
 {
     "metadata": {
@@ -10,7 +12,8 @@
     "techniques": {
         "default": {
             "surfaceShader": { 
-                "source": [ "MaterialX.Surface" ]
+                "source": [ "SurfaceHelpers.TangentSpace",
+                            "MaterialX.Surface" ]
             }
         }
     }
@@ -112,13 +115,21 @@ void mxInit(vec4 Peye, vec3 Neye)
     // Convert HdData to MxData
     u_viewPosition = vec3(HdGet_worldToViewInverseMatrix() * vec4(0.0, 0.0, 0.0, 1.0));
 
-    // Calculate a worldspace tangent vector
+    // Calculate the worldspace position and normal vectors
+    vec3 positionWorld = vec3(HdGet_worldToViewInverseMatrix() * Peye);
     vec3 normalWorld = vec3(HdGet_worldToViewInverseMatrix() * vec4(Neye, 0.0));
+
+    // Calculate the worldspace tangent vector 
+#ifdef HD_HAS_st
+    vec3 tangentWorld = ComputeTangentVector(positionWorld, normalWorld, HdGet_st());
+#else 
     vec3 tangentWorld = cross(normalWorld, vec3(0, 1, 0));
     if (length(tangentWorld) < M_FLOAT_EPS) {
         tangentWorld = cross(normalWorld, vec3(1, 0, 0));
     }
-    vd = mxVertexData(tangentWorld,normalWorld,vec3(HdGet_worldToViewInverseMatrix() * Peye));
+#endif
+
+    vd = mxVertexData(tangentWorld,normalWorld,positionWorld);
 
     // Initialize Material Parameters
     diffuseColor = HdGet_diffuseColor();