PostProcessDownsample.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "ScreenPass.h"
 
class FEyeAdaptationParameters;
 
enum class EDownsampleFlags : uint8
{
    None = 0,
 
    // Forces the downsample pass to run on the raster pipeline, regardless of view settings.
    ForceRaster = 0x1
};
ENUM_CLASS_FLAGS(EDownsampleFlags);
 
enum class EDownsampleQuality : uint8
{
    // Single filtered sample (2x2 tap).
    Low,
 
    // Four filtered samples (4x4 tap).
    High,
 
    MAX
};
 
// The set of inputs needed to add a downsample pass to RDG.
struct FDownsamplePassInputs
{
    FDownsamplePassInputs() = default;
 
    // Friendly name of the pass. Used for logging and profiling.
    const TCHAR* Name = nullptr;
 
    // Optional user supplied output buffer.
    IPooledRenderTarget* UserSuppliedOutput = nullptr;
 
    // Input scene color RDG texture / view rect. Must not be null.
    FScreenPassTextureSlice SceneColor;
 
    // The downsample method to use.
    EDownsampleQuality Quality = EDownsampleQuality::Low;
 
    // Flags to control how the downsample pass is run.
    EDownsampleFlags Flags = EDownsampleFlags::None;
 
    // The format to use for the output texture (if unknown, the input format is used).
    EPixelFormat FormatOverride = PF_Unknown;
};
 
FScreenPassTexture AddDownsamplePass(FRDGBuilder& GraphBuilder, const FViewInfo& View, const FDownsamplePassInputs& Inputs);
 
void AddDownsampleComputePass(FRDGBuilder& GraphBuilder, const FViewInfo& View, FScreenPassTexture Input, FScreenPassTexture Output, EDownsampleQuality Quality, ERDGPassFlags PassFlags);
void AddDownsampleComputePass(FRDGBuilder& GraphBuilder, const FViewInfo& View, FScreenPassTextureSlice Input, FScreenPassTexture Output, EDownsampleQuality Quality, ERDGPassFlags PassFlags);
 
 
class FTextureDownsampleChain
{
public:
    FTextureDownsampleChain() = default;
 
    void Init(
        FRDGBuilder& GraphBuilder,
        const FViewInfo& View,
        const FEyeAdaptationParameters& EyeAdaptationParameters,
        FScreenPassTextureSlice InputTexture,
        EDownsampleQuality DownsampleQuality,
        uint32 StageCount,
        bool bLogLumaInAlpha,
        const TCHAR* TextureName = nullptr,
        uint32 InputResolutionExponent = 0);
 
    bool IsInitialized() const
    {
        return bInitialized;
    }
 
    FScreenPassTextureSlice GetTexture(uint32 StageIndex) const
    {
        return Textures[StageIndex];
    }
 
    FScreenPassTextureSlice GetFirstTexture() const
    {
        return Textures[0];
    }
 
    FScreenPassTextureSlice GetLastTexture() const
    {
        return Textures.Last();
    }
 
    uint32 GetStageCount() const
    {
        return Textures.Num();
    }
 
private:
    TArray<FScreenPassTextureSlice> Textures;
    bool bInitialized = false;
};