Override aggregated struct generation for MDL (#2261)

Add a custom StructTypeSyntax implementation for MDL.

Author: krohmerNV

source/MaterialXGenMdl/MdlShaderGenerator.cpp

@@ -816,6 +816,19 @@ void MdlShaderGenerator::emitMdlVersionFilenameSuffix(GenContext& context, Shade
     emitString(getMdlVersionFilenameSuffix(context), stage);
 }
 
+void MdlShaderGenerator::emitTypeDefinitions(GenContext&, ShaderStage& stage) const
+{
+    // Emit typedef statements for all data types that have an alias
+    for (const auto& syntax : _syntax->getTypeSyntaxes())
+    {
+        if (!syntax->getTypeDefinition().empty())
+        {
+            stage.addLine("export " + syntax->getTypeDefinition(), false);
+        }
+    }
+    stage.newLine();
+}
+
 namespace MDL
 {
 // Identifiers for MDL variable blocks

source/MaterialXGenMdl/MdlShaderGenerator.h

@@ -100,6 +100,9 @@ class MX_GENMDL_API MdlShaderGenerator : public ShaderGenerator
     /// Get the version number suffix appended to MDL modules that use versions.
     const string& getMdlVersionFilenameSuffix(GenContext& context) const;
 
+    /// Emit type definitions for all data types that need them.
+    void emitTypeDefinitions(GenContext& context, ShaderStage& stage) const override;
+
   protected:
     // Create and initialize a new MDL shader for shader generation.
     ShaderPtr createShader(const string& name, ElementPtr element, GenContext& context) const;

source/MaterialXGenMdl/MdlSyntax.cpp

@@ -615,4 +615,41 @@ const string& MdlSyntax::getMdlVersionSuffixMarker() const
     return MARKER_MDL_VERSION_SUFFIX;
 }
 
+StructTypeSyntaxPtr MdlSyntax::createStructSyntax(const string& structTypeName, const string& defaultValue,
+                                                  const string& uniformDefaultValue, const string& typeAlias,
+                                                  const string& typeDefinition) const
+{
+    return std::make_shared<MdlStructTypeSyntax>(
+        this,
+        structTypeName,
+        defaultValue,
+        uniformDefaultValue,
+        typeAlias,
+        typeDefinition);
+}
+
+string MdlStructTypeSyntax::getValue(const Value& value, bool /* uniform */) const
+{
+    const AggregateValue& aggValue = static_cast<const AggregateValue&>(value);
+
+    string result = aggValue.getTypeString() + "(";
+
+    string separator = "";
+    for (const auto& memberValue : aggValue.getMembers())
+    {
+        result += separator;
+        separator = ", ";
+
+        const string& memberTypeName = memberValue->getTypeString();
+        const TypeDesc memberTypeDesc = _parent->getType(memberTypeName);
+
+        // Recursively use the syntax to generate the output, so we can supported nested structs.
+        result += _parent->getValue(memberTypeDesc, *memberValue, true);
+    }
+
+    result += ")";
+
+    return result;
+}
+
 MATERIALX_NAMESPACE_END

source/MaterialXGenMdl/MdlSyntax.h

@@ -29,6 +29,10 @@ class MX_GENMDL_API MdlSyntax : public Syntax
 
     static SyntaxPtr create(TypeSystemPtr typeSystem) { return std::make_shared<MdlSyntax>(typeSystem); }
 
+    StructTypeSyntaxPtr createStructSyntax(const string& structTypeName, const string& defaultValue,
+                                           const string& uniformDefaultValue, const string& typeAlias,
+                                           const string& typeDefinition) const override;
+
     const string& getConstantQualifier() const override { return CONST_QUALIFIER; };
     const string& getUniformQualifier() const override { return UNIFORM_QUALIFIER; };
     const string& getSourceFileExtension() const override { return SOURCE_FILE_EXTENSION; };
@@ -77,6 +81,16 @@ class MX_GENMDL_API MdlSyntax : public Syntax
     const string& getMdlVersionSuffixMarker() const;
 };
 
+/// @class MdlStructTypeSyntax
+/// Specialization of TypeSyntax for aggregate types.
+class MX_GENMDL_API MdlStructTypeSyntax : public StructTypeSyntax
+{
+  public:
+    using StructTypeSyntax::StructTypeSyntax;
+
+    string getValue(const Value& value, bool uniform) const override;
+};
+
 namespace Type
 {