Add support for viewdirection space in hardware shading (#2036)

This addresses issue #1656. Previously, attribute `space` in node `viewdirection_vector3` was unused by GLSL and MSL implementations. This change correctly transforms the view direction from world space to the specified space.
AcademySoftwareFoundation · Oct 3, 2024 · 860b8d4 · 860b8d4
1 parent 0653e1d
commit 860b8d4
Showing 1 changed file with 22 additions and 4 deletions.
diff --git a/source/MaterialXGenShader/Nodes/HwViewDirectionNode.cpp b/source/MaterialXGenShader/Nodes/HwViewDirectionNode.cpp
@@ -14,20 +14,31 @@ ShaderNodeImplPtr HwViewDirectionNode::create()
     return std::make_shared<HwViewDirectionNode>();
 }
 
-void HwViewDirectionNode::createVariables(const ShaderNode&, GenContext&, Shader& shader) const
+void HwViewDirectionNode::createVariables(const ShaderNode& node, GenContext&, Shader& shader) const
 {
     ShaderStage& vs = shader.getStage(Stage::VERTEX);
     ShaderStage& ps = shader.getStage(Stage::PIXEL);
 
     addStageInput(HW::VERTEX_INPUTS, Type::VECTOR3, HW::T_IN_POSITION, vs);
-    addStageConnector(HW::VERTEX_DATA, Type::VECTOR3, HW::T_POSITION_WORLD, vs, ps);
+
+    const ShaderInput* spaceInput = node.getInput(SPACE);
+    const int space = spaceInput ? spaceInput->getValue()->asA<int>() : OBJECT_SPACE;
+
     addStageUniform(HW::PRIVATE_UNIFORMS, Type::VECTOR3, HW::T_VIEW_POSITION, ps);
+    addStageConnector(HW::VERTEX_DATA, Type::VECTOR3, HW::T_POSITION_WORLD, vs, ps);
+    if (space == OBJECT_SPACE || space == MODEL_SPACE)
+    {
+        addStageUniform(HW::PRIVATE_UNIFORMS, Type::MATRIX44, HW::T_WORLD_INVERSE_TRANSPOSE_MATRIX, ps);
+    }
 }
 
 void HwViewDirectionNode::emitFunctionCall(const ShaderNode& node, GenContext& context, ShaderStage& stage) const
 {
     const HwShaderGenerator& shadergen = static_cast<const HwShaderGenerator&>(context.getShaderGenerator());
 
+    const ShaderInput* spaceInput = node.getInput(SPACE);
+    const int space = spaceInput ? spaceInput->getValue()->asA<int>() : OBJECT_SPACE;
+
     DEFINE_SHADER_STAGE(stage, Stage::VERTEX)
     {
         VariableBlock& vertexData = stage.getOutputBlock(HW::VERTEX_DATA);
@@ -44,10 +55,17 @@ void HwViewDirectionNode::emitFunctionCall(const ShaderNode& node, GenContext& c
     {
         VariableBlock& vertexData = stage.getInputBlock(HW::VERTEX_DATA);
         const string prefix = shadergen.getVertexDataPrefix(vertexData);
-        ShaderPort* position = vertexData[HW::T_POSITION_WORLD];
         shadergen.emitLineBegin(stage);
         shadergen.emitOutput(node.getOutput(), true, false, context, stage);
-        shadergen.emitString(" = normalize(" + prefix + position->getVariable() + " - " + HW::T_VIEW_POSITION + ")", stage);
+        ShaderPort* position = vertexData[HW::T_POSITION_WORLD];
+        if (space == WORLD_SPACE)
+        {
+            shadergen.emitString(" = normalize(" + prefix + position->getVariable() + " - " + HW::T_VIEW_POSITION + ")", stage);
+        }
+        else
+        {
+            shadergen.emitString(" = normalize((" + HW::T_WORLD_INVERSE_TRANSPOSE_MATRIX + " * vec4(" + prefix + position->getVariable() + " - " + HW::T_VIEW_POSITION + ", 0.0)).xyz)", stage);
+        }
         shadergen.emitLineEnd(stage);
     }
 }