VolumeRendering.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
/*=============================================================================
    VolumeRendering.h: Volume rendering definitions.
=============================================================================*/
 
#pragma once
 
#include "Shader.h"
#include "ShaderCompilerCore.h"
#include "ShaderParameters.h"
#include "GlobalShader.h"
#include "ShaderParameterUtils.h"
#include "ScreenRendering.h"
 
struct FVolumeBounds
{
    int32 MinX, MinY, MinZ;
    int32 MaxX, MaxY, MaxZ;
 
    FVolumeBounds() :
        MinX(0),
        MinY(0),
        MinZ(0),
        MaxX(0),
        MaxY(0),
        MaxZ(0)
    {}
 
    FVolumeBounds(int32 Max) :
        MinX(0),
        MinY(0),
        MinZ(0),
        MaxX(Max),
        MaxY(Max),
        MaxZ(Max)
    {}
 
    bool IsValid() const
    {
        return MaxX > MinX && MaxY > MinY && MaxZ > MinZ;
    }
};
 
class FWriteToSliceVS : public FGlobalShader
{
    DECLARE_EXPORTED_GLOBAL_SHADER(FWriteToSliceVS, ENGINE_API);
public:
    FWriteToSliceVS();
    FWriteToSliceVS(const ShaderMetaType::CompiledShaderInitializerType& Initializer);
 
    static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters);
    static void ModifyCompilationEnvironment(const FGlobalShaderPermutationParameters& Parameters, FShaderCompilerEnvironment& OutEnvironment);
 
    void SetParameters(FRHIBatchedShaderParameters& BatchedParameters, const FVolumeBounds& VolumeBounds, const FIntVector& VolumeResolution)
    {
        const float InvVolumeResolutionX = 1.0f / VolumeResolution.X;
        const float InvVolumeResolutionY = 1.0f / VolumeResolution.Y;
        SetShaderValue(BatchedParameters, UVScaleBias, FVector4f(
            (VolumeBounds.MaxX - VolumeBounds.MinX) * InvVolumeResolutionX,
            (VolumeBounds.MaxY - VolumeBounds.MinY) * InvVolumeResolutionY,
            VolumeBounds.MinX * InvVolumeResolutionX,
            VolumeBounds.MinY * InvVolumeResolutionY));
        SetShaderValue(BatchedParameters, MinZ, VolumeBounds.MinZ);
    }
 
private:
    LAYOUT_FIELD(FShaderParameter, UVScaleBias);
    LAYOUT_FIELD(FShaderParameter, MinZ);
};
 
class FWriteToSliceGS : public FGlobalShader
{
    DECLARE_EXPORTED_GLOBAL_SHADER(FWriteToSliceGS, ENGINE_API);
public:
    FWriteToSliceGS();
    FWriteToSliceGS(const ShaderMetaType::CompiledShaderInitializerType& Initializer);
 
    static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters);
 
    void SetParameters(FRHIBatchedShaderParameters& BatchedParameters, int32 MinZValue)
    {
        SetShaderValue(BatchedParameters, MinZ, MinZValue);
    }
 
private:
    LAYOUT_FIELD(FShaderParameter, MinZ);
};
 
// This function assumes the PSO had a PrimitiveType of PT_TriangleStrip
extern ENGINE_API void RasterizeToVolumeTexture(FRHICommandList& RHICmdList, FVolumeBounds VolumeBounds);
 
class FVolumeRasterizeVertexBuffer : public FVertexBuffer
{
public:
    ENGINE_API virtual void InitRHI(FRHICommandListBase& RHICmdList) override;
};
 
extern ENGINE_API TGlobalResource<FVolumeRasterizeVertexBuffer> GVolumeRasterizeVertexBuffer;