SplineMeshSceneResources.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "SpanAllocator.h"
#include "SceneUniformBuffer.h"
#include "RHIShaderPlatform.h"
#include "RendererInterface.h"
#include "Containers/Map.h"
#include "RenderGraphResources.h"
#include "SceneExtensions.h"
 
struct IPooledRenderTarget;
 
class FSplineMeshSceneExtension : public ISceneExtension
{
    friend class FSplineMeshSceneUpdater;
    friend class FSplineMeshSceneRenderer;
 
    DECLARE_SCENE_EXTENSION(RENDERER_API, FSplineMeshSceneExtension);
 
public:
    using ISceneExtension::ISceneExtension;
 
    static bool ShouldCreateExtension(FScene& InScene);
    
    virtual ISceneExtensionUpdater* CreateUpdater() override;
    virtual ISceneExtensionRenderer* CreateRenderer(FSceneRendererBase& InSceneRenderer, const FEngineShowFlags& EngineShowFlags) override;
 
    uint32 NumRegisteredPrimitives() const { return RegisteredPrimitives.Num(); }
 
private:
    struct FPrimitiveSlot
    {
        uint32 FirstSplineIndex = INDEX_NONE;
        uint32 NumSplines = 0;
    };
    using FPrimitiveSlotMap = TMap<const FPrimitiveSceneInfo*, FPrimitiveSlot>;
 
    FPrimitiveSlot& Register(const FPrimitiveSceneInfo& PrimitiveSceneInfo);
    void Unregister(const FPrimitiveSceneInfo& PrimitiveSceneInfo);
    void AllocTextureSpace(const FPrimitiveSceneInfo& PrimitiveSceneInfo, uint32 NumSplines, FPrimitiveSlot& OutSlot);
    static uint32 GetNumSplines(const FPrimitiveSceneInfo& SceneInfo);
    void AssignCoordinates(const FPrimitiveSceneInfo& SceneInfo, const FPrimitiveSlot& Slot);
    template<typename TSplineMeshSceneProxy>
    void AssignCoordinates(TSplineMeshSceneProxy* SceneProxy, const FPrimitiveSlot& Slot);
    void DefragTexture();
    FRDGBufferSRVRef GetInstanceIdLookupSRV(FRDGBuilder& GraphBuilder, bool bForceUpdate);
    void ClearAllCache();
 
private:
    FPrimitiveSlotMap RegisteredPrimitives;
    TArray<uint32> RegisteredInstanceIds;
    FSpanAllocator SlotAllocator;
    TRefCountPtr<IPooledRenderTarget> SavedPosTexture;
    TRefCountPtr<IPooledRenderTarget> SavedRotTexture;
    TRefCountPtr<FRDGPooledBuffer> SavedIdLookup;
    bool bInstanceLookupDirty = true;
    bool bOverflowError = false;
};
 
class FSplineMeshSceneUpdater : public ISceneExtensionUpdater
{
    DECLARE_SCENE_EXTENSION_UPDATER(FSplineMeshSceneUpdater, FSplineMeshSceneExtension);
 
public:
    FSplineMeshSceneUpdater(FSplineMeshSceneExtension& InSceneData) : SceneData(&InSceneData) {}
 
    virtual void PreSceneUpdate(FRDGBuilder& GraphBuilder, const FScenePreUpdateChangeSet& ChangeSet, FSceneUniformBuffer& SceneUniforms) override;
    virtual void PostSceneUpdate(FRDGBuilder& GraphBuilder, const FScenePostUpdateChangeSet& ChangeSet) override;
    virtual void PostGPUSceneUpdate(FRDGBuilder& GraphBuilder, FSceneUniformBuffer& SceneUniforms) override;
 
private:
    void AddUpdatePass(
        FRDGBuilder& GraphBuilder,
        FSceneUniformBuffer& SceneUniforms,
        FRDGTextureRef PosTexture,
        FRDGTextureRef RotTexture,
        FVector2f Extent,
        FVector2f InvExtent,
        bool bFullUpdate,
        bool bForceUpdate
    );
 
    FSplineMeshSceneExtension* SceneData = nullptr;
    TArray<uint32, FSceneRenderingArrayAllocator> UpdateRequests;
};
 
class FSplineMeshSceneRenderer : public ISceneExtensionRenderer
{
    DECLARE_SCENE_EXTENSION_RENDERER(FSplineMeshSceneRenderer, FSplineMeshSceneExtension);
 
public:
    FSplineMeshSceneRenderer(FSceneRendererBase& InSceneRenderer, FSplineMeshSceneExtension& InSceneData) : ISceneExtensionRenderer(InSceneRenderer), SceneData(&InSceneData) {}
    virtual void UpdateSceneUniformBuffer(FRDGBuilder& GraphBuilder, FSceneUniformBuffer& SceneUniforms) override;
 
private:
    FSplineMeshSceneExtension* SceneData = nullptr;
};