215 lines
9.2 KiB
Markdown
215 lines
9.2 KiB
Markdown
---
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title: 参考SubsurfaceProfile 模改ToonDataAsset
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date: 2023-02-04 20:38:39
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excerpt:
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tags:
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rating: ⭐⭐
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---
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# 原理
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## PreShader
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在材质编译期，将名为 **__SubsurfaceProfile** 的Uniform表达式塞入材质中。
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```c++
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int32 FHLSLMaterialTranslator::NumericParameter(EMaterialParameterType ParameterType, FName ParameterName, const UE::Shader::FValue& InDefaultValue)
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{
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const UE::Shader::EValueType ValueType = GetShaderValueType(ParameterType);
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check(InDefaultValue.GetType() == ValueType);
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UE::Shader::FValue DefaultValue(InDefaultValue);
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// If we're compiling a function, give the function a chance to override the default parameter value
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FMaterialParameterMetadata Meta;
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if (GetParameterOverrideValueForCurrentFunction(ParameterType, ParameterName, Meta))
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{
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DefaultValue = Meta.Value.AsShaderValue();
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check(DefaultValue.GetType() == ValueType);
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}
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const uint32* PrevDefaultOffset = DefaultUniformValues.Find(DefaultValue);
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uint32 DefaultOffset;
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if (PrevDefaultOffset)
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{
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DefaultOffset = *PrevDefaultOffset;
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}
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else
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{
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DefaultOffset = MaterialCompilationOutput.UniformExpressionSet.AddDefaultParameterValue(DefaultValue);
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DefaultUniformValues.Add(DefaultValue, DefaultOffset);
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}
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FMaterialParameterInfo ParameterInfo = GetParameterAssociationInfo();
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ParameterInfo.Name = ParameterName;
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const int32 ParameterIndex = MaterialCompilationOutput.UniformExpressionSet.FindOrAddNumericParameter(ParameterType, ParameterInfo, DefaultOffset);
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return AddUniformExpression(new FMaterialUniformExpressionNumericParameter(ParameterInfo, ParameterIndex), GetMaterialValueType(ParameterType), TEXT(""));
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}
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```
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`const int32 ParameterIndex = MaterialCompilationOutput.UniformExpressionSet.FindOrAddNumericParameter(ParameterType, ParameterInfo, DefaultOffset);`
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`return AddUniformExpression(new FMaterialUniformExpressionNumericParameter(ParameterInfo, ParameterIndex), GetMaterialValueType(ParameterType), TEXT(""));`
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之后在`Chunk[MP_SubsurfaceColor] = AppendVector(SubsurfaceColor, CodeSubsurfaceProfile);`将结果编译成`MaterialFloat4(MaterialFloat3(1.00000000,1.00000000,1.00000000),Material.PreshaderBuffer[2].x)`
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## 填充PreShader结构体
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1. 从MeshDraw框架的FMeshElementCollector::AddMesh()开始，执行`MeshBatch.MaterialRenderProxy->UpdateUniformExpressionCacheIfNeeded(Views[ViewIndex]->GetFeatureLevel());`，开始更新材质的UniformExpression。
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2. `FMaterialRenderProxy::UpdateUniformExpressionCacheIfNeeded()`：取得材质指针之后评估材质表达式。
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3. `FMaterialRenderProxy::EvaluateUniformExpressions()`：从渲染线程取得材质的ShaderMap，再从ShaderMap取得UniformExpressionSet。
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4. `FUniformExpressionSet::FillUniformBuffer`：Dump preshader results into buffer.
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1. FEmitContext::EmitPreshaderOrConstant：PreshaderHeader = &UniformExpressionSet.UniformPreshaders.AddDefaulted_GetRef();
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# 将ToonData的ID塞入材质
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存在问题，如何将SubsurfaceProfile Asset的ID塞入材质中：
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```c++
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int32 FMaterialCompiler::ScalarParameter(FName ParameterName, float DefaultValue)
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{
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return NumericParameter(EMaterialParameterType::Scalar, ParameterName, DefaultValue);
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}
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int32 FHLSLMaterialTranslator::NumericParameter(EMaterialParameterType ParameterType, FName ParameterName, const UE::Shader::FValue& InDefaultValue)
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{
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const UE::Shader::EValueType ValueType = GetShaderValueType(ParameterType);
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check(InDefaultValue.GetType() == ValueType);
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UE::Shader::FValue DefaultValue(InDefaultValue);
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// If we're compiling a function, give the function a chance to override the default parameter value
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FMaterialParameterMetadata Meta;
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if (GetParameterOverrideValueForCurrentFunction(ParameterType, ParameterName, Meta))
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{ DefaultValue = Meta.Value.AsShaderValue();
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check(DefaultValue.GetType() == ValueType);
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}
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const uint32* PrevDefaultOffset = DefaultUniformValues.Find(DefaultValue);
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uint32 DefaultOffset;
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if (PrevDefaultOffset)
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{
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DefaultOffset = *PrevDefaultOffset;
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}else
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{
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DefaultOffset = MaterialCompilationOutput.UniformExpressionSet.AddDefaultParameterValue(DefaultValue);
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DefaultUniformValues.Add(DefaultValue, DefaultOffset);
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}
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FMaterialParameterInfo ParameterInfo = GetParameterAssociationInfo();
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ParameterInfo.Name = ParameterName;
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const int32 ParameterIndex = MaterialCompilationOutput.UniformExpressionSet.FindOrAddNumericParameter(ParameterType, ParameterInfo, DefaultOffset);
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return AddUniformExpression(new FMaterialUniformExpressionNumericParameter(ParameterInfo, ParameterIndex), GetMaterialValueType(ParameterType), TEXT(""));
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}
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bool FMaterialHLSLGenerator::GetParameterOverrideValueForCurrentFunction(EMaterialParameterType ParameterType, FName ParameterName, FMaterialParameterMetadata& OutResult) const
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{
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bool bResult = false;
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if (!ParameterName.IsNone())
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{ // Give every function in the callstack on opportunity to override the parameter value
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// Parameters in outer functions take priority // For example, if a layer instance calls a function instance that includes an overriden parameter, we want to use the value from the layer instance rather than the function instance for (const FFunctionCallEntry* FunctionEntry : FunctionCallStack)
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{ const UMaterialFunctionInterface* CurrentFunction = FunctionEntry->MaterialFunction;
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if (CurrentFunction)
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{
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if (CurrentFunction->GetParameterOverrideValue(ParameterType, ParameterName, OutResult))
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{ bResult = true;
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break;
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}
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}
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}
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}
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return bResult;
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}
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// Finds a parameter by name from the game thread, traversing the chain up to the BaseMaterial.
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FScalarParameterValue* GameThread_GetScalarParameterValue(UMaterialInstance* MaterialInstance, FName Name)
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{
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UMaterialInterface* It = 0;
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FMaterialParameterInfo ParameterInfo(Name); // @TODO: This will only work for non-layered parameters
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while(MaterialInstance)
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{
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if(FScalarParameterValue* Ret = GameThread_FindParameterByName(MaterialInstance->ScalarParameterValues, ParameterInfo))
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{
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return Ret;
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}
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It = MaterialInstance->Parent;
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MaterialInstance = Cast<UMaterialInstance>(It);
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}
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return 0;
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}
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template <typename ParameterType>
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ParameterType* GameThread_FindParameterByName(TArray<ParameterType>& Parameters, const FHashedMaterialParameterInfo& ParameterInfo)
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{
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for (int32 ParameterIndex = 0; ParameterIndex < Parameters.Num(); ParameterIndex++)
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{
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ParameterType* Parameter = &Parameters[ParameterIndex];
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if (Parameter->ParameterInfo == ParameterInfo)
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{
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return Parameter;
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}
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}
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return NULL;
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}
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void UMaterialFunctionInstance::OverrideMaterialInstanceParameterValues(UMaterialInstance* Instance)
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{
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// Dynamic parameters
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Instance->ScalarParameterValues = ScalarParameterValues;
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Instance->VectorParameterValues = VectorParameterValues;
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Instance->DoubleVectorParameterValues = DoubleVectorParameterValues;
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Instance->TextureParameterValues = TextureParameterValues;
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Instance->RuntimeVirtualTextureParameterValues = RuntimeVirtualTextureParameterValues;
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Instance->FontParameterValues = FontParameterValues;
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// Static parameters
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FStaticParameterSet StaticParametersOverride = Instance->GetStaticParameters();
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StaticParametersOverride.EditorOnly.StaticSwitchParameters = StaticSwitchParameterValues;
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StaticParametersOverride.EditorOnly.StaticComponentMaskParameters = StaticComponentMaskParameterValues;
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Instance->UpdateStaticPermutation(StaticParametersOverride);
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}
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```
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和UMaterialExpressionStrataLegacyConversion::Compile()无关。
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GetSubsurfaceProfileParameterName()
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__SubsurfaceProfile
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1. 在FHLSLMaterialTranslator::Translate() => NumericParameter()会往MaterialCompilationOutput.UniformExpressionSet以及DefaultUniformValues添加默认值以及Offset。最终会调用AddUniformExpression()
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## MaterialRenderProxy
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```c++
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void SetSubsurfaceProfileRT(const USubsurfaceProfile* Ptr) { SubsurfaceProfileRT = Ptr; }
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const USubsurfaceProfile* GetSubsurfaceProfileRT() const { return SubsurfaceProfileRT; }
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/** 0 if not set, game thread pointer, do not dereference, only for comparison */
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const USubsurfaceProfile* SubsurfaceProfileRT;
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```
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## UMaterialInterface
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```c++
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uint8 bOverrideSubsurfaceProfile:1;//UE5转移至UMaterialInstance中
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TObjectPtr<class USubsurfaceProfile> SubsurfaceProfile;
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void UMaterialInterface::UpdateMaterialRenderProxy(FMaterialRenderProxy& Proxy)
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//还有所有子类实现 UMaterialInstance、UMaterial
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USubsurfaceProfile* UMaterialInterface::GetSubsurfaceProfile_Internal() const
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```
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## MaterialShared.h
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```c++
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inline bool UseSubsurfaceProfile(FMaterialShadingModelField ShadingModel)
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{
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return ShadingModel.HasShadingModel(MSM_SubsurfaceProfile) || ShadingModel.HasShadingModel(MSM_Eye);
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}
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```
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## UMaterial
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```c++
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USubsurfaceProfile* UMaterial::GetSubsurfaceProfile_Internal() const
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{
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checkSlow(IsInGameThread());
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return SubsurfaceProfile;
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}
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```
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## UMaterialInstance
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```c++
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UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = MaterialInstance)
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uint8 bOverrideSubsurfaceProfile:1;
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``` |