PostProcessAmbientOcclusion.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
 
/*=============================================================================
    PostProcessAmbientOcclusion.h: Post processing ambient occlusion implementation.
=============================================================================*/
 
#pragma once
 
#include "ScreenPass.h"
#include "UniformBuffer.h"
#include "RendererInterface.h"
#include "HZB.h"
 
class FViewInfo;
 
struct FRDGSystemTextures;
 
enum class ESSAOType
{
    // pixel shader
    EPS,
    // non async compute shader
    ECS,
    // async compute shader
    EAsyncCS,
};
 
enum class EGTAOType
{
    // Not on (use legacy if at all)
    EOff,
 
    // Async compute shader where the Horizon Search and Inner Integrate are combined and the spatial filter is run on the Async Pipe
    // Temporal and Upsample are run on the GFX Pipe as Temporal requires velocity Buffer
    EAsyncCombinedSpatial,
 
    // Async compute shader where the Horizon Search is run on the Async compute pipe
    // Integrate, Spatial, Temporal and Upsample are run on the GFX pipe as these require GBuffer channels
    EAsyncHorizonSearch,
 
    // Non async version where all passes are run on the GFX Pipe
    ENonAsync,
};
 
enum EGTAOPass
{
    EGTAOPass_None                      = 0x0,
    EGTAOPass_HorizonSearch             = 0x1,
    EGTAOPass_HorizonSearchIntegrate    = 0x2,
    EGTAOPass_Integrate                 = 0x4,
    EGTAOPass_SpatialFilter             = 0x8,
    EGTAOPass_TemporalFilter            = 0x10,
    EGTAOPass_Upsample                  = 0x20,
};
 
FRDGTextureDesc GetScreenSpaceAOTextureDesc(ERHIFeatureLevel::Type FeatureLevel, FIntPoint Extent);
 
FRDGTextureRef CreateScreenSpaceAOTexture(FRDGBuilder& GraphBuilder, ERHIFeatureLevel::Type FeatureLevel, FIntPoint Extent);
 
FRDGTextureRef GetScreenSpaceAOFallback(const FRDGSystemTextures& SystemTextures);
 
class FGTAOContext
{
public:
    EGTAOType GTAOType;
    uint32 FinalPass;
    uint32 DownsampleFactor;
 
    bool bUseNormals;
    bool bHalfRes;
    bool bHasSpatialFilter;
    bool bHasTemporalFilter;
 
    FGTAOContext(EGTAOType Type);
    FGTAOContext();
 
    bool IsFinalPass(EGTAOPass);
};
 
 
class FSSAOHelper
{
public:
 
    // Utility functions for deciding AO logic.
    // for render thread
    // @return usually in 0..100 range but could be outside, combines the view with the cvar setting
    static float GetAmbientOcclusionQualityRT(const FSceneView& View);
 
    // @return returns actual shader quality level to use. 0-4 currently.
    static int32 GetAmbientOcclusionShaderLevel(const FSceneView& View);
 
    // @return whether AmbientOcclusion should run a compute shader.
    static bool IsAmbientOcclusionCompute(const ERHIFeatureLevel::Type FeatureLevel);
 
    static int32 GetNumAmbientOcclusionLevels();
    static float GetAmbientOcclusionStepMipLevelFactor();
    static EAsyncComputeBudget GetAmbientOcclusionAsyncComputeBudget();
 
    static bool IsBasePassAmbientOcclusionRequired(const FViewInfo& View);
    static bool IsAmbientOcclusionAsyncCompute(const FViewInfo& View, uint32 AOPassCount);
 
    // @return 0:off, 0..3
    static uint32 ComputeAmbientOcclusionPassCount(const FViewInfo& View);
 
    static EGTAOType GetGTAOPassType(const FViewInfo& View, uint32 Levels);
};
 
// SSAO
 
struct FSSAOCommonParameters
{
    TRDGUniformBufferRef<FSceneTextureUniformParameters> SceneTexturesUniformBuffer = nullptr;
    FScreenPassTextureViewport SceneTexturesViewport;
 
    FScreenPassTexture GBufferA;
    FScreenPassTexture SceneDepth;
 
    uint32 Levels = 1;
    int32 ShaderQuality = 4;
    ESSAOType DownscaleType = ESSAOType::EPS;
    ESSAOType FullscreenType = ESSAOType::EPS;
    bool bNeedSmoothingPass = true;
};
 
FScreenPassTexture AddAmbientOcclusionSetupPass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FSSAOCommonParameters& CommonParameters,
    FScreenPassTexture Input);
 
FScreenPassTexture AddAmbientOcclusionStepPass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FSSAOCommonParameters& CommonParameters,
    const FScreenPassTexture& Input0,
    const FScreenPassTexture& Input1,
    const FScreenPassTexture& Input2);
 
FScreenPassTexture AddAmbientOcclusionFinalPass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FSSAOCommonParameters& CommonParameters,
    const FScreenPassTexture& Input0,
    const FScreenPassTexture& Input1,
    const FScreenPassTexture& Input2,
    FScreenPassRenderTarget FinalOutput);
 
// GTAO
 
struct FGTAOCommonParameters
{
    TRDGUniformBufferRef<FSceneTextureUniformParameters> SceneTexturesUniformBuffer = nullptr;
    FScreenPassTextureViewport SceneTexturesViewport;
    
    FScreenPassTexture SceneDepth;
    FScreenPassTexture SceneVelocity;
 
    FIntRect DownsampledViewRect;
 
    int32 ShaderQuality = 4;
    uint32 DownscaleFactor = 1;
    EGTAOType GTAOType = EGTAOType::EOff;
};
 
struct FGTAOHorizonSearchOutputs
{
    FScreenPassTexture Color;
};
 
FGTAOHorizonSearchOutputs AddGTAOHorizonSearchPass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FGTAOCommonParameters& CommonParameters,
    FScreenPassTexture SceneDepth,
    FScreenPassRenderTarget HorizonOutput);
 
FScreenPassTexture AddGTAOInnerIntegratePass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FGTAOCommonParameters& CommonParameters,
    FScreenPassTexture SceneDepth,
    FScreenPassTexture HorizonsTexture);
 
FGTAOHorizonSearchOutputs AddGTAOHorizonSearchIntegratePass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FGTAOCommonParameters& CommonParameters,
    FScreenPassTexture SceneDepth);
 
struct FGTAOTemporalOutputs
{
    FScreenPassRenderTarget OutputAO;
 
    FIntPoint TargetExtent;
    FIntRect ViewportRect;
};
 
FGTAOTemporalOutputs AddGTAOTemporalPass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FGTAOCommonParameters& CommonParameters,
    FScreenPassTexture Input,
    FScreenPassTexture SceneDepth,
    FScreenPassTexture SceneVelocity,
    FScreenPassTexture HistoryColor,
    FScreenPassTextureViewport HistoryViewport);
 
FScreenPassTexture AddGTAOSpatialFilter(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    const FGTAOCommonParameters& CommonParameters,
    FScreenPassTexture Input,
    FScreenPassTexture InputDepth,
    FScreenPassRenderTarget SuggestedOutput = FScreenPassRenderTarget());
 
FScreenPassTexture AddGTAOUpsamplePass(
    FRDGBuilder& GraphBuilder,
    const FViewInfo& View,
    FScreenPassTexture Input,
    FScreenPassTexture SceneDepth,
    FScreenPassRenderTarget Output);
 
BEGIN_SHADER_PARAMETER_STRUCT(FTextureBinding, )
    SHADER_PARAMETER_RDG_TEXTURE(Texture2D, Texture)
    SHADER_PARAMETER(FIntPoint, TextureSize)
    SHADER_PARAMETER(FVector2f, InverseTextureSize)
END_SHADER_PARAMETER_STRUCT();
 
enum class EAOTechnique
{
    SSAO,
    GTAO,
};
 
FHZBParameters GetHZBParametersForAO(FRDGBuilder& GraphBuilder, const FViewInfo& View, FIntPoint InputTextureSize, EAOTechnique AOTechnique);