Emit layout blocks for stage interfaces in Vulkan (#2274)

The VkShaderGenerator was earlier flattening the VertexData into separate layout entries. While this is valid syntax, it is preferred to use the same struct as glsl to be consistent.

Author: ashwinbhat

.github/workflows/main.yml

@@ -198,6 +198,7 @@ jobs:
         python Scripts/mxdoc.py --docType md ../libraries/pbrlib/pbrlib_defs.mtlx
         python Scripts/mxdoc.py --docType html ../libraries/bxdf/standard_surface.mtlx
         python Scripts/generateshader.py ../resources/Materials/Examples/StandardSurface --target glsl
+        python Scripts/generateshader.py ../resources/Materials/Examples/StandardSurface --target vulkan
         python Scripts/generateshader.py ../resources/Materials/Examples/StandardSurface --target osl
         python Scripts/generateshader.py ../resources/Materials/Examples/StandardSurface --target mdl
         python Scripts/generateshader.py ../resources/Materials/Examples/StandardSurface --target msl
@@ -209,7 +210,8 @@ jobs:
         C:/vcpkg/vcpkg install glslang[tools] --triplet=x64-windows-release
         C:/vcpkg/installed/x64-windows-release/tools/glslang/glslangValidator.exe -v
         python python/Scripts/generateshader.py resources/Materials/Examples --target glsl --validator C:/vcpkg/installed/x64-windows-release/tools/glslang/glslangValidator.exe
-        python python/Scripts/generateshader.py resources/Materials/Examples --target essl --validator C:/vcpkg/installed/x64-windows-release/tools/glslang/glslangValidator.exe
+        python python/Scripts/generateshader.py resources/Materials/Examples/StandardSurface --target essl --validator C:/vcpkg/installed/x64-windows-release/tools/glslang/glslangValidator.exe
+        python python/Scripts/generateshader.py resources/Materials/Examples/StandardSurface --target vulkan --validator C:/vcpkg/installed/x64-windows-release/tools/glslang/glslangValidator.exe
 
     - name: Shader Validation Tests (MacOS)
       if: matrix.test_shaders == 'ON' && runner.os == 'macOS'

source/MaterialXGenGlsl/VkShaderGenerator.cpp

@@ -54,16 +54,14 @@ void VkShaderGenerator::emitInputs(GenContext& context, ShaderStage& stage) cons
         const VariableBlock& vertexData = stage.getInputBlock(HW::VERTEX_DATA);
         if (!vertexData.empty())
         {
-            emitComment("Inputs: " + vertexData.getName(), stage);
-            for (size_t i = 0; i < vertexData.size(); ++i)
-            {
-
-                emitLineBegin(stage);
-                emitString("layout (location = " + std::to_string(i) + ") ", stage);
-                emitVariableDeclaration(vertexData[i], _syntax->getInputQualifier(), context, stage, false);
-                emitString(Syntax::SEMICOLON, stage);
-                emitLineEnd(stage, false);
-            }
+            emitString("layout (location = " + std::to_string(vertexDataLocation) + ") " +
+                        _syntax->getInputQualifier() + " " + vertexData.getName(), stage);
+            emitLineBreak(stage);
+            emitScopeBegin(stage);
+            emitVariableDeclarations(vertexData, EMPTY_STRING, Syntax::SEMICOLON, context, stage, false);
+            emitScopeEnd(stage, false, false);
+            emitString(" " + vertexData.getInstance() + Syntax::SEMICOLON, stage);
+            emitLineBreak(stage);
             emitLineBreak(stage);
         }
     }
@@ -81,14 +79,14 @@ void VkShaderGenerator::emitOutputs(GenContext& context, ShaderStage& stage) con
         const VariableBlock& vertexData = stage.getOutputBlock(HW::VERTEX_DATA);
         if (!vertexData.empty())
         {
-            for (size_t i = 0; i < vertexData.size(); ++i)
-            {
-                emitLineBegin(stage);
-                emitString("layout (location = " + std::to_string(i) + ") ", stage);
-                emitVariableDeclaration(vertexData[i], _syntax->getOutputQualifier(), context, stage, false);
-                emitString(Syntax::SEMICOLON, stage);
-                emitLineEnd(stage, false);
-            }
+            emitString("layout (location = " + std::to_string(vertexDataLocation) + ") " +
+                        _syntax->getOutputQualifier() + " " + vertexData.getName(), stage);
+            emitLineBreak(stage);
+            emitScopeBegin(stage);
+            emitVariableDeclarations(vertexData, EMPTY_STRING, Syntax::SEMICOLON, context, stage, false);
+            emitScopeEnd(stage, false, false);
+            emitString(" " + vertexData.getInstance() + Syntax::SEMICOLON, stage);
+            emitLineBreak(stage);
             emitLineBreak(stage);
         }
     }

source/MaterialXGenGlsl/VkShaderGenerator.h

@@ -57,6 +57,9 @@ class MX_GENGLSL_API VkShaderGenerator : public GlslShaderGenerator
     HwResourceBindingContextPtr getResourceBindingContext(GenContext&) const override;
 
     VkResourceBindingContextPtr _resourceBindingCtx = nullptr;
+
+    // Vertex data interface location to bind between stages
+    int vertexDataLocation = 0;
 };
 
 MATERIALX_NAMESPACE_END