ViewData.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "ShaderParameterMacros.h"
#include "SceneUniformBuffer.h"
//#include "Nanite/NaniteShared.h"
 
class FViewInfo;
class FRDGBuilder;
class FScene;
class FGPUScene;
 
namespace Nanite
{
    struct FPackedView;
    struct FPackedViewParams;
}
 
namespace RendererViewData
{
 
BEGIN_SHADER_PARAMETER_STRUCT(FCommonParameters, RENDERER_API)
    // InViews represents the scene renderer primary views (passed to FRendererViewDataManager constructor), and are named "InViews" to be compatible with Nanite conventions (see GetNaniteView),
    // The buffer may also contain all the non-primary views but these are not generally accessible.
    SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< FPackedNaniteView >, InViews)
    SHADER_PARAMETER(int32, MaxPersistentViewId)
    // Number of scene renderer primary views.
    SHADER_PARAMETER(uint32, NumSceneRendererPrimaryViews)
    // Stride between each bit vector in the per-view bit masks in dwords.
    SHADER_PARAMETER(uint32, InstanceMaskWordStride)
END_SHADER_PARAMETER_STRUCT()
 
BEGIN_SHADER_PARAMETER_STRUCT(FParameters, RENDERER_API)
    SHADER_PARAMETER_STRUCT_INCLUDE(FCommonParameters, Common)
    SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer<uint>, DeformingInstanceViewMask)
    SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer<uint>, PersistentIdToIndexMap)
END_SHADER_PARAMETER_STRUCT()
 
 
BEGIN_SHADER_PARAMETER_STRUCT(FWriterParameters, RENDERER_API)
    SHADER_PARAMETER_STRUCT_INCLUDE(FCommonParameters, Common)
    SHADER_PARAMETER_RDG_BUFFER_UAV(RWStructuredBuffer<uint>, OutDeformingInstanceViewMask)
END_SHADER_PARAMETER_STRUCT()
 
 
BEGIN_SHADER_PARAMETER_STRUCT(FCullingShaderParameters, )
    SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer< FPackedNaniteView >, InViews)
    SHADER_PARAMETER(uint32, NumSceneRendererPrimaryViews)
    SHADER_PARAMETER(uint32, NumCullingViews)
END_SHADER_PARAMETER_STRUCT()
 
}
 
DECLARE_SCENE_UB_STRUCT(RendererViewData::FParameters, ViewData, RENDERER_API)
 
 
class FRendererViewDataManager
{
public:
    FRendererViewDataManager(FRDGBuilder& GraphBuilder, const FScene& InScene, FSceneUniformBuffer& InSceneUniforms, TArray<FViewInfo*> &InOutSceneRendererPrimaryViews);
 
    bool IsEnabled() const { return bIsEnabled; }
 
    int32 RegisterView(const Nanite::FPackedViewParams& Params);
 
    // Allocate space for views ahead of time prior to calling RegisterView.
    void AllocateViews(int32 NumViews);
 
    void InitInstanceState(FRDGBuilder& GraphBuilder);
 
    RendererViewData::FCullingShaderParameters GetCullingParameters(FRDGBuilder& GraphBuilder);
 
    RendererViewData::FWriterParameters GetWriterShaderParameters(FRDGBuilder& GraphBuilder) const { return WriterShaderParameters; }
    
    void FlushRegisteredViews(FRDGBuilder& GraphBuilder);
 
    const TArray<FViewInfo*> &GetRegisteredPrimaryViews() const { return SceneRendererPrimaryViews; }
 
    int32 GetNumCullingViews() const { return NumRegisteredViews.load(std::memory_order_relaxed); }
 
 
private:
 
    // Register a primary view
    int32 RegisterPrimaryView(const FViewInfo& ViewInfo);
 
    FRendererViewDataManager() = delete;
    FRendererViewDataManager(FRendererViewDataManager&) = delete;
 
    const FScene& Scene;
    const FGPUScene& GPUScene;
    FSceneUniformBuffer& SceneUniforms;
    TArray<FViewInfo*> &SceneRendererPrimaryViews;
 
    std::atomic_int32_t NumRegisteredViews = {0};
    TArray<Nanite::FPackedView> CullingViews;
    bool bIsEnabled;
 
    FRDGBuffer* CullingViewsRDG = nullptr;
    FRDGBuffer* PrimaryViewsRDG = nullptr;
    int32 NumSceneRendererPrimaryViews = 0;
    int32 InstanceMaskWordStride = 0;
    // Non view index strided buffer of bits, one per instance that is deforming (animating or something like that), indexed by InstanceId.
    // Initialized to zero each frame & updated by interested scene extensions / systems.
    // Also in the same buffer laid out after the above
    // 1. counter of number of instances marked & 
    FRDGBuffer* DeformingInstanceViewMaskRDG = nullptr;
    FRDGBuffer* PersistentIdToIndexMapRDG = nullptr;
 
    RendererViewData::FCullingShaderParameters CullingShaderParameters;
    RendererViewData::FParameters   ShaderParameters;
    RendererViewData::FWriterParameters WriterShaderParameters;
};