Shader compilation code flow

• Initializes FHLSLMaterialTranslator()

• Set up which material properties are shared (ex: SharedPixelProperties[MP_Normal] = true;)

• Calls FHLSLMaterialTranslator::Translate(): Translate from Material Node graph into textual shader code representation

• Material->GatherExpressionsForCustomInterpolators(Expressions);

• GatherCustomVertexInterpolators(Expressions);

• Material->GatherCustomOutputExpressions(CustomOutputExpressions);

• CompileCustomOutputs(CustomOutputExpressions, SeenCustomOutputExpressionsClases, true);

• Material->CompilePropertyAndSetMaterialProperty() on MP_Normal, MP_DiffuseColor, MP_Specular, MP_Roughness, etc

• Determines if properties are actually used && validation checking. Eg:

  bUsesEmissiveColor = IsMaterialPropertyUsed(MP_EmissiveColor, Chunk[MP_EmissiveColor], FLinearColor(0, 0, 0, 0), 3);

• Determines number of vertex interpolators/uv tex coords/etc

• MaterialCompilationOutput.UniformExpressionSet.SetParameterCollections(ParameterCollections);

• MaterialCompilationOutput.UniformExpressionSet.CreateBufferStruct();

• Calls FHLSLMaterialTranslator::GetMaterialEnvironment()

• Sets more fundamental defines such as: NEEDS_PARTICLE_POSITION, NEEDS_SCENE_TEXTURES, USES_TRANSFORM_VECTOR, USES_EMISSIVE_COLOR

• Add uniform buffer declarations for any parameter collections referenced

  const FString CollectionName = FString::Printf(TEXT("MaterialCollection%u"), CollectionIndex);

  FShaderUniformBufferParameter::ModifyCompilationEnvironment(*CollectionName, ParameterCollections[CollectionIndex]->GetUniformBufferStruct(), InPlatform, OutEnvironment);

• Calls FHLSLMaterialTranslator::GetMaterialShaderCode():

• Responsible for compiling and filling MaterialTemplate.ush

• Uses LazyPrintf.PushParam() and Printf() to stringify everything into the generated Material.ush file

• GetSharedInputsMaterialCode():

  • Generates the fields for FPixelMaterialInputs which are shared properties across the shader (like MP_Normal, MP_BaseColor, MP_Roughness, etc)

  • Generates initializers for them too

• Calls main compilation in NewShaderMap->Compile():

• Material->SetupMaterialEnvironment(): Sets majority of shader defines (including material specific ones like staticswitches, etc) by calling. Ex:

• Defines from the umaterial uproperties such as: MATERIAL_TWOSIDED, MATERIAL_NONMETAL, MATERIAL_HQ_FORWARD_REFLECTIONS

• Defines from the material itself such as: GetBlendMode() => MATERIALBLENDING_MASKED|MATERIALBLENDING_SOLID, MATERIAL_FULLY_ROUGH

• Defines also fundamental things such as MATERIAL_DOMAIN_SURFACE|MATERIAL_DOMAIN_DEFERREDDECAL|… & MATERIAL_SHADINGMODEL_UNLIT|MATERIAL_SHADINGMODEL_DEFAULT_LIT|…

• Also uses cvar values to determine whether to set defines or not: r.StencilForLODDither => USE_STENCIL_LOD_DITHER_DEFAULT

• Iterate over all vertex factories and materials and compile them together if this material applies