373 lines
14 KiB
Markdown
373 lines
14 KiB
Markdown
---
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title: 基于插件的StaticMesh多Pass绘制方案
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date: 2022-11-04 10:26:59
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excerpt:
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tags:
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rating: ⭐
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---
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## 前言
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StaticMesh与SkeletalMesh的实现方法比较类似，不过两者的绘制方式有很大的不同。不过庆幸的是，Static的MeshBatch设置在绘制函数的外面。
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## 思路说明
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### 创建自定义StaticMeshComponent
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1. 继承UStaticMeshComponent,重写GetUsedMaterials与CreateSceneProxy函数。
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2. 添加用于多pass渲染的UMaterialInterface指针。（NeedSecondPass变量其实可以不用，因为既然你要使用这个类，那肯定要启用这个功能）
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```c++
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#pragma once
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#include "CoreMinimal.h"
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#include "Engine/Classes/Components/StaticMeshComponent.h"
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#include "StrokeStaticMeshComponent.generated.h"
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UCLASS(ClassGroup=(Rendering, Common), hidecategories=Object, editinlinenew, meta=(BlueprintSpawnableComponent))
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class UStrokeStaticMeshComponent : public UStaticMeshComponent
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{
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GENERATED_UCLASS_BODY()
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//~ Begin UPrimitiveComponent Interface
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virtual void GetUsedMaterials(TArray<UMaterialInterface*>& OutMaterials, bool bGetDebugMaterials = false) const override;
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virtual FPrimitiveSceneProxy* CreateSceneProxy() override;
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//~ End UPrimitiveComponent Interface
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public:
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MultiplePass")
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UMaterialInterface* SecondPassMaterial = nullptr;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MultiplePass")
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bool NeedSecondPass=false;
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};
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```
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3. 实现GetUsedMaterials与CreateSceneProxy函数，并包含相应头文件。
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### 头文件
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```
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#include "StrokeStaticMeshSceneProxy.h"
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```
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### GetUsedMaterials
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```c++
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void UStrokeStaticMeshComponent::GetUsedMaterials(TArray<UMaterialInterface*>& OutMaterials, bool bGetDebugMaterials /*= false*/) const
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{
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if (GetStaticMesh() && GetStaticMesh()->RenderData)
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{
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TMap<int32, UMaterialInterface*> MapOfMaterials;
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for (int32 LODIndex = 0; LODIndex < GetStaticMesh()->RenderData->LODResources.Num(); LODIndex++)
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{
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FStaticMeshLODResources& LODResources = GetStaticMesh()->RenderData->LODResources[LODIndex];
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int32 MaterialNum = 0;
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for (int32 SectionIndex = 0; SectionIndex < LODResources.Sections.Num(); SectionIndex++)
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{
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// Get the material for each element at the current lod index
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int32 MaterialIndex = LODResources.Sections[SectionIndex].MaterialIndex;
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if (!MapOfMaterials.Contains(MaterialIndex))
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{
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MapOfMaterials.Add(MaterialIndex, GetMaterial(MaterialIndex));
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MaterialNum++;
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}
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}
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//这里是我添加的代码
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if (NeedSecondPass)
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{
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bool NeedAddMaterial = true;
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for (int i = 0; i < MapOfMaterials.Num(); ++i)
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{
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if (MapOfMaterials[i]== SecondPassMaterial)
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{
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NeedAddMaterial = false;
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}
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}
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if (NeedAddMaterial)
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{
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MapOfMaterials.Add(MaterialNum, SecondPassMaterial);
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}
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}
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}
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if (MapOfMaterials.Num() > 0)
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{
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//We need to output the material in the correct order (follow the material index)
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//So we sort the map with the material index
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MapOfMaterials.KeySort([](int32 A, int32 B) {
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return A < B; // sort keys in order
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});
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//Preadd all the material item in the array
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OutMaterials.AddZeroed(MapOfMaterials.Num());
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//Set the value in the correct order
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int32 MaterialIndex = 0;
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for (auto Kvp : MapOfMaterials)
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{
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OutMaterials[MaterialIndex++] = Kvp.Value;
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}
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}
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}
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}
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```
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### CreateSceneProxy
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```c++
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FPrimitiveSceneProxy* UStrokeStaticMeshComponent::CreateSceneProxy()
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{
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if (GetStaticMesh() == nullptr || GetStaticMesh()->RenderData == nullptr)
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{
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return nullptr;
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}
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const TIndirectArray<FStaticMeshLODResources>& LODResources = GetStaticMesh()->RenderData->LODResources;
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if (LODResources.Num() == 0 || LODResources[FMath::Clamp<int32>(GetStaticMesh()->MinLOD.Default, 0, LODResources.Num() - 1)].VertexBuffers.StaticMeshVertexBuffer.GetNumVertices() == 0)
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{
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return nullptr;
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}
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//与SkeletalMeshComponent中写的类似，直接通过new来创建
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FPrimitiveSceneProxy* Proxy = ::new FStrokeStaticMeshSceneProxy(this, false);
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#if STATICMESH_ENABLE_DEBUG_RENDERING
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SendRenderDebugPhysics(Proxy);
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#endif
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return Proxy;
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}
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```
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### 创建自定义StaticMeshSceneProxy
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**这里与SkeletalMeshSceneProxy不同，GetDynamicMeshElements没有起到绘制作用，真正起到作用的是DrawStaticElements。**
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1. 继承FStaticMeshSceneProxy,重写DrawStaticElements函数。
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2. 定义UStaticMeshComponent指针，用于获取自定义StaticMeshComponent的变量。（之后使用需要使用强制转换）
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```c++
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#pragma once
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#include "Engine\Public\StaticMeshResources.h"
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class FStrokeStaticMeshSceneProxy : public FStaticMeshSceneProxy
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{
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public:
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//在UStrokeStaticMeshComponent中调用这个构造函数初始化
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FStrokeStaticMeshSceneProxy(UStaticMeshComponent* Component, bool bForceLODsShareStaticLighting);
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virtual void DrawStaticElements(FStaticPrimitiveDrawInterface* PDI) override;
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private:
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UPROPERTY()
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const UStaticMeshComponent* ComponentPtr;
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};
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```
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3. 复制DrawStaticElements中所需函数的代码。
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将Engine\Source\Runtime\Engine\Private\StaticMeshRender.cpp中的AllowShadowOnlyMesh、UseLightPropagationVolumeRT2函数代码复制到你定义的StaticMeshSceneProxy类所在的cpp文件中。
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4. 实现DrawStaticElements函数，并包含头文件。
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与SkeletalMesh的绘制函数不同，它有3处需要调用绘制函数的地方。其中有一处因为不存在lod所以代码有些不同，所以请不要在未测试的情况下使用本插件进行生产项目。
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不过一个好消息是，我们可以在绘制前设置MeshBatch，从而完美结局描边问题。
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```c++
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void FStrokeStaticMeshSceneProxy::DrawStaticElements(FStaticPrimitiveDrawInterface* PDI)
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{
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checkSlow(IsInParallelRenderingThread());
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if (!HasViewDependentDPG())
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{
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// Determine the DPG the primitive should be drawn in.
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uint8 PrimitiveDPG = GetStaticDepthPriorityGroup();
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int32 NumLODs = RenderData->LODResources.Num();
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//Never use the dynamic path in this path, because only unselected elements will use DrawStaticElements
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bool bIsMeshElementSelected = false;
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const auto FeatureLevel = GetScene().GetFeatureLevel();
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//check if a LOD is being forced
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if (ForcedLodModel > 0)
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{
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int32 LODIndex = FMath::Clamp(ForcedLodModel, ClampedMinLOD + 1, NumLODs) - 1;
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const FStaticMeshLODResources& LODModel = RenderData->LODResources[LODIndex];
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// Draw the static mesh elements.
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for (int32 SectionIndex = 0; SectionIndex < LODModel.Sections.Num(); SectionIndex++)
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{
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#if WITH_EDITOR
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if (GIsEditor)
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{
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const FLODInfo::FSectionInfo& Section = LODs[LODIndex].Sections[SectionIndex];
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bIsMeshElementSelected = Section.bSelected;
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PDI->SetHitProxy(Section.HitProxy);
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}
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#endif // WITH_EDITOR
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const int32 NumBatches = GetNumMeshBatches();
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PDI->ReserveMemoryForMeshes(NumBatches);
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for (int32 BatchIndex = 0; BatchIndex < NumBatches; BatchIndex++)
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{
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FMeshBatch MeshBatch;
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if (GetMeshElement(LODIndex, BatchIndex, SectionIndex, PrimitiveDPG, bIsMeshElementSelected, true, MeshBatch))
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{
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PDI->DrawMesh(MeshBatch, FLT_MAX);
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//以下是我添加的代码
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const FLODInfo& ProxyLODInfo = LODs[LODIndex];
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UMaterialInterface* MaterialInterface = ProxyLODInfo.Sections[SectionIndex].Material;
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const UStrokeStaticMeshComponent* StrokeStaticMeshComponent = dynamic_cast<const UStrokeStaticMeshComponent *>(ComponentPtr);
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if (MaterialInterface == StrokeStaticMeshComponent->SecondPassMaterial)
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{
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continue;
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}
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if (StrokeStaticMeshComponent->NeedSecondPass) {
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if (StrokeStaticMeshComponent->SecondPassMaterial == nullptr) {
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continue;
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}
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MeshBatch.MaterialRenderProxy = StrokeStaticMeshComponent->SecondPassMaterial->GetRenderProxy();
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//设置反转剔除选项
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MeshBatch.ReverseCulling = true;
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PDI->DrawMesh(MeshBatch, FLT_MAX);
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}
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}
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}
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}
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}
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else //no LOD is being forced, submit them all with appropriate cull distances
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{
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for (int32 LODIndex = ClampedMinLOD; LODIndex < NumLODs; LODIndex++)
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{
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const FStaticMeshLODResources& LODModel = RenderData->LODResources[LODIndex];
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float ScreenSize = GetScreenSize(LODIndex);
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bool bUseUnifiedMeshForShadow = false;
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bool bUseUnifiedMeshForDepth = false;
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if (GUseShadowIndexBuffer && LODModel.bHasDepthOnlyIndices)
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{
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const FLODInfo& ProxyLODInfo = LODs[LODIndex];
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// The shadow-only mesh can be used only if all elements cast shadows and use opaque materials with no vertex modification.
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// In some cases (e.g. LPV) we don't want the optimization
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bool bSafeToUseUnifiedMesh = AllowShadowOnlyMesh(FeatureLevel);
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bool bAnySectionUsesDitheredLODTransition = false;
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bool bAllSectionsUseDitheredLODTransition = true;
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bool bIsMovable = IsMovable();
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bool bAllSectionsCastShadow = bCastShadow;
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for (int32 SectionIndex = 0; bSafeToUseUnifiedMesh && SectionIndex < LODModel.Sections.Num(); SectionIndex++)
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{
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const FMaterial* Material = ProxyLODInfo.Sections[SectionIndex].Material->GetRenderProxy()->GetMaterial(FeatureLevel);
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// no support for stateless dithered LOD transitions for movable meshes
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bAnySectionUsesDitheredLODTransition = bAnySectionUsesDitheredLODTransition || (!bIsMovable && Material->IsDitheredLODTransition());
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bAllSectionsUseDitheredLODTransition = bAllSectionsUseDitheredLODTransition && (!bIsMovable && Material->IsDitheredLODTransition());
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const FStaticMeshSection& Section = LODModel.Sections[SectionIndex];
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bSafeToUseUnifiedMesh =
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!(bAnySectionUsesDitheredLODTransition && !bAllSectionsUseDitheredLODTransition) // can't use a single section if they are not homogeneous
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&& Material->WritesEveryPixel()
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&& !Material->IsTwoSided()
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&& !IsTranslucentBlendMode(Material->GetBlendMode())
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&& !Material->MaterialModifiesMeshPosition_RenderThread()
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&& Material->GetMaterialDomain() == MD_Surface;
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bAllSectionsCastShadow &= Section.bCastShadow;
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}
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if (bSafeToUseUnifiedMesh)
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{
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bUseUnifiedMeshForShadow = bAllSectionsCastShadow;
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// Depth pass is only used for deferred renderer. The other conditions are meant to match the logic in FDepthPassMeshProcessor::AddMeshBatch.
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bUseUnifiedMeshForDepth = ShouldUseAsOccluder() && GetScene().GetShadingPath() == EShadingPath::Deferred && !IsMovable();
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if (bUseUnifiedMeshForShadow || bUseUnifiedMeshForDepth)
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{
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const int32 NumBatches = GetNumMeshBatches();
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PDI->ReserveMemoryForMeshes(NumBatches);
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for (int32 BatchIndex = 0; BatchIndex < NumBatches; BatchIndex++)
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{
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FMeshBatch MeshBatch;
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if (GetShadowMeshElement(LODIndex, BatchIndex, PrimitiveDPG, MeshBatch, bAllSectionsUseDitheredLODTransition))
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{
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bUseUnifiedMeshForShadow = bAllSectionsCastShadow;
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MeshBatch.CastShadow = bUseUnifiedMeshForShadow;
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MeshBatch.bUseForDepthPass = bUseUnifiedMeshForDepth;
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MeshBatch.bUseAsOccluder = bUseUnifiedMeshForDepth;
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MeshBatch.bUseForMaterial = false;
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PDI->DrawMesh(MeshBatch, ScreenSize);
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//以下是我添加的代码
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const FLODInfo& ProxyLODInfo = LODs[LODIndex];
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UMaterialInterface* MaterialInterface = ProxyLODInfo.Sections[0].Material;
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const UStrokeStaticMeshComponent* StrokeStaticMeshComponent = dynamic_cast<const UStrokeStaticMeshComponent *>(ComponentPtr);
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if (MaterialInterface == StrokeStaticMeshComponent->SecondPassMaterial)
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{
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continue;
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}
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if (StrokeStaticMeshComponent->NeedSecondPass) {
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if (StrokeStaticMeshComponent->SecondPassMaterial == nullptr) {
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continue;
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}
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//通过MeshBatch设置Material与反转剔除选项
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MeshBatch.MaterialRenderProxy = StrokeStaticMeshComponent->SecondPassMaterial->GetRenderProxy();
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//设置反转剔除选项
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MeshBatch.ReverseCulling = true;
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PDI->DrawMesh(MeshBatch, FLT_MAX);
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}
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}
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}
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}
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}
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}
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// Draw the static mesh elements.
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for (int32 SectionIndex = 0; SectionIndex < LODModel.Sections.Num(); SectionIndex++)
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{
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#if WITH_EDITOR
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if (GIsEditor)
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{
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const FLODInfo::FSectionInfo& Section = LODs[LODIndex].Sections[SectionIndex];
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bIsMeshElementSelected = Section.bSelected;
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PDI->SetHitProxy(Section.HitProxy);
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}
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#endif // WITH_EDITOR
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const int32 NumBatches = GetNumMeshBatches();
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PDI->ReserveMemoryForMeshes(NumBatches);
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for (int32 BatchIndex = 0; BatchIndex < NumBatches; BatchIndex++)
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{
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FMeshBatch MeshBatch;
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if (GetMeshElement(LODIndex, BatchIndex, SectionIndex, PrimitiveDPG, bIsMeshElementSelected, true, MeshBatch))
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{
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// If we have submitted an optimized shadow-only mesh, remaining mesh elements must not cast shadows.
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MeshBatch.CastShadow &= !bUseUnifiedMeshForShadow;
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MeshBatch.bUseAsOccluder &= !bUseUnifiedMeshForDepth;
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MeshBatch.bUseForDepthPass &= !bUseUnifiedMeshForDepth;
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PDI->DrawMesh(MeshBatch, ScreenSize);
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//以下是我添加的代码
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const FLODInfo& ProxyLODInfo = LODs[LODIndex];
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UMaterialInterface* MaterialInterface = ProxyLODInfo.Sections[SectionIndex].Material;
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const UStrokeStaticMeshComponent* StrokeStaticMeshComponent = dynamic_cast<const UStrokeStaticMeshComponent *>(ComponentPtr);
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if (MaterialInterface == StrokeStaticMeshComponent->SecondPassMaterial)
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{
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continue;
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}
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if (StrokeStaticMeshComponent->NeedSecondPass) {
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if (StrokeStaticMeshComponent->SecondPassMaterial == nullptr) {
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continue;
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}
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MeshBatch.MaterialRenderProxy = StrokeStaticMeshComponent->SecondPassMaterial->GetRenderProxy();
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//
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MeshBatch.ReverseCulling = true;
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PDI->DrawMesh(MeshBatch, FLT_MAX);
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}
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}
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}
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}
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}
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}
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}
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}
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```
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## 插件地址及使用方法
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### 插件地址
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https://github.com/blueroseslol/BRPlugins
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### 使用方法
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1. 创建一个Actor蓝图。
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2. 创建你定义的StaticMeshComponent。
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3. 赋予轮廓材质，并勾选NeedSecondPass。
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使用这个材质的效果： |