SkyAtmosphereRendering.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
 
/*=============================================================================
    SkyAtmosphereRendering.h
=============================================================================*/
 
#pragma once
 
#include "EngineDefines.h"
#include "RenderGraph.h"
#include "RenderResource.h"
#include "Rendering/SkyAtmosphereCommonData.h"
#include "RenderGraphResources.h"
#include "SceneView.h"
#include "VirtualShadowMaps/VirtualShadowMapArray.h"
 
 
class FScene;
class FViewInfo;
class FLightSceneInfo;
class FVisibleLightInfo;
class USkyAtmosphereComponent;
class FSkyAtmosphereSceneProxy;
class FProjectedShadowInfo;
 
class FSkyAtmosphereInternalCommonParameters;
class FVolumeShadowingShaderParametersGlobal0;
class FVolumeShadowingShaderParametersGlobal1;
 
struct FScreenPassTexture;
struct FEngineShowFlags;
 
DECLARE_UNIFORM_BUFFER_STRUCT(FSceneUniformParameters, RENDERER_API)
 
 
// Use as a global shader parameter struct and also the CPU structure representing the atmosphere it self.
// This is static for a version of a component. When a component is changed/tweaked, it is recreated.
BEGIN_GLOBAL_SHADER_PARAMETER_STRUCT(FAtmosphereUniformShaderParameters, )
    SHADER_PARAMETER(float, MultiScatteringFactor)
    SHADER_PARAMETER(float, BottomRadiusKm)
    SHADER_PARAMETER(float, TopRadiusKm)
    SHADER_PARAMETER(float, RayleighDensityExpScale)
    SHADER_PARAMETER(FLinearColor, RayleighScattering)
    SHADER_PARAMETER(FLinearColor, MieScattering)
    SHADER_PARAMETER(float, MieDensityExpScale)
    SHADER_PARAMETER(FLinearColor, MieExtinction)
    SHADER_PARAMETER(float, MiePhaseG)
    SHADER_PARAMETER(FLinearColor, MieAbsorption)
    SHADER_PARAMETER(float, AbsorptionDensity0LayerWidth)
    SHADER_PARAMETER(float, AbsorptionDensity0ConstantTerm)
    SHADER_PARAMETER(float, AbsorptionDensity0LinearTerm)
    SHADER_PARAMETER(float, AbsorptionDensity1ConstantTerm)
    SHADER_PARAMETER(float, AbsorptionDensity1LinearTerm)
    SHADER_PARAMETER(FLinearColor, AbsorptionExtinction)
    SHADER_PARAMETER(FLinearColor, GroundAlbedo)
END_GLOBAL_SHADER_PARAMETER_STRUCT()
 
// These parameters are shared on the view global uniform buffer and are dynamically changed with cvars.
struct FSkyAtmosphereViewSharedUniformShaderParameters
{
    FVector4f CameraAerialPerspectiveVolumeSizeAndInvSize;
    float AerialPerspectiveStartDepthKm;
    float CameraAerialPerspectiveVolumeDepthResolution;
    float CameraAerialPerspectiveVolumeDepthResolutionInv;
    float CameraAerialPerspectiveVolumeDepthSliceLengthKm;
    float CameraAerialPerspectiveVolumeDepthSliceLengthKmInv;
    float ApplyCameraAerialPerspectiveVolume;
};
 
// Structure with data necessary to specify a sky render.
struct FSkyAtmosphereRenderContext
{
    // Per scene parameters
 
    bool bUseDepthBoundTestIfPossible;
    bool bForceRayMarching;
    bool bDepthReadDisabled;// Do not apply scene depth texture. As such, only far Z will be considered
    bool bDisableBlending;  // Do not do any blending. The sky will clear the target when rendering a sky reflection capture for instance.
    bool bFastSky;
    bool bFastAerialPerspective;
    bool bFastAerialPerspectiveDepthTest;
    bool bSecondAtmosphereLightEnabled;
    bool bShouldSampleOpaqueShadow;
 
    FRDGTextureRef TransmittanceLut;
    FRDGTextureRef MultiScatteredLuminanceLut;
    FRDGTextureRef SkyAtmosphereViewLutTexture;
    FRDGTextureRef SkyAtmosphereCameraAerialPerspectiveVolume;
    FRDGTextureRef SkyAtmosphereCameraAerialPerspectiveVolumeMieOnly;
    FRDGTextureRef SkyAtmosphereCameraAerialPerspectiveVolumeRayOnly;
 
    // Per view parameters
 
    FViewMatrices* ViewMatrices;            // The actual view matrices we use to render the sky
    TUniformBufferRef<FViewUniformShaderParameters> ViewUniformBuffer;
    TRDGUniformBufferRef<FSceneUniformParameters> SceneUniformBuffer;
    bool bSceneHasSkyMaterial;
 
    FRenderTargetBindingSlots RenderTargets;
 
    FIntRect Viewport;
 
    bool bIsReflectionCapture;
    bool bRenderSkyPixel;
    float AerialPerspectiveStartDepthInCm;
    float NearClippingDistance;
    ERHIFeatureLevel::Type FeatureLevel;
 
    TRDGUniformBufferRef<FVolumeShadowingShaderParametersGlobal0> LightShadowShaderParams0UniformBuffer{};
    TRDGUniformBufferRef<FVolumeShadowingShaderParametersGlobal1> LightShadowShaderParams1UniformBuffer{};
 
    int VirtualShadowMapId0 = INDEX_NONE;
    int VirtualShadowMapId1 = INDEX_NONE;
 
    bool bShouldSampleCloudShadow;
    FRDGTextureRef VolumetricCloudShadowMap[2];
 
    bool bShouldSampleCloudSkyAO;
    FRDGTextureRef VolumetricCloudSkyAO;
 
    bool bAPOnCloudMode;
    FRDGTextureRef VolumetricCloudDepthTexture;
    FRDGTextureRef InputCloudLuminanceTransmittanceTexture;
 
    uint8 MSAASampleCount;
    FRDGTextureRef MSAADepthTexture;
 
    FSkyAtmosphereRenderContext();
 
private:
};
 
 
 
class FSkyAtmosphereRenderSceneInfo
{
public:
 
    explicit FSkyAtmosphereRenderSceneInfo(FSkyAtmosphereSceneProxy& SkyAtmosphereSceneProxy);
    ~FSkyAtmosphereRenderSceneInfo();
 
    const TUniformBufferRef<FAtmosphereUniformShaderParameters>& GetAtmosphereUniformBuffer() { return AtmosphereUniformBuffer; }
    TRefCountPtr<IPooledRenderTarget>& GetTransmittanceLutTexture() { return TransmittanceLutTexture; }
    TRefCountPtr<IPooledRenderTarget>& GetMultiScatteredLuminanceLutTexture() { return MultiScatteredLuminanceLutTexture; }
 
    void CreateDistantSkyLightLutBufferAndSRV(FRDGBuilder& GraphBuilder);
    TRefCountPtr<FRDGPooledBuffer>& GetDistantSkyLightLutBuffer();
    TRefCountPtr<FRDGPooledBuffer>& GetMobileDistantSkyLightLutBuffer();
    FRHIShaderResourceView* GetDistantSkyLightLutBufferSRV();
    FRHIShaderResourceView* GetMobileDistantSkyLightLutBufferSRV();
 
    FRDGTextureRef GetTransmittanceLutTexture(FRDGBuilder& GraphBuilder) const { return GraphBuilder.RegisterExternalTexture(TransmittanceLutTexture); }
 
    const FAtmosphereUniformShaderParameters* GetAtmosphereShaderParameters() const { return &AtmosphereUniformShaderParameters; }
    const FSkyAtmosphereSceneProxy& GetSkyAtmosphereSceneProxy() const { return SkyAtmosphereSceneProxy; }
 
    TUniformBufferRef<FSkyAtmosphereInternalCommonParameters>& GetInternalCommonParametersUniformBuffer() { return InternalCommonParametersUniformBuffer; }
 
private:
 
    FSkyAtmosphereSceneProxy& SkyAtmosphereSceneProxy;
 
    FAtmosphereUniformShaderParameters AtmosphereUniformShaderParameters;
 
    TUniformBufferRef<FAtmosphereUniformShaderParameters> AtmosphereUniformBuffer;
 
    TUniformBufferRef<FSkyAtmosphereInternalCommonParameters> InternalCommonParametersUniformBuffer;
 
    TRefCountPtr<IPooledRenderTarget> TransmittanceLutTexture;
    TRefCountPtr<IPooledRenderTarget> MultiScatteredLuminanceLutTexture;
    TRefCountPtr<FRDGPooledBuffer> DistantSkyLightLutBuffer;
    FRHIShaderResourceView* DistantSkyLightLutBufferSRV = nullptr;
    TRefCountPtr<FRDGPooledBuffer> MobileDistantSkyLightLutBuffer;
    FRHIShaderResourceView* MobileDistantSkyLightLutBufferSRV = nullptr;
};
 
class FSkyAtmospherePendingRDGResources
{
public:
    // Sky env map capture uses the view UB, which contains the LUTs computed above. We need to transition them to readable now.
    void CommitToSceneAndViewUniformBuffers(FRDGBuilder& GraphBuilder, FRDGExternalAccessQueue& ExternalAccessQueue) const;
 
private:
    struct FViewRDGResources
    {
        FRDGTextureRef SkyAtmosphereViewLutTexture = nullptr;
        FRDGTextureRef SkyAtmosphereCameraAerialPerspectiveVolume = nullptr;
    };
 
    FSceneRenderer* SceneRenderer = nullptr;
    TArray<FViewRDGResources, TInlineAllocator<4>> ViewResources;
 
    FRDGBufferRef DistantSkyLightLutBuffer = nullptr;
    FRDGBufferRef MobileDistantSkyLightLutBuffer = nullptr;
    FRDGTextureRef RealTimeReflectionCaptureSkyAtmosphereViewLutTexture = nullptr;
    FRDGTextureRef RealTimeReflectionCaptureCamera360APLutTexture = nullptr;
 
    FRDGTextureRef TransmittanceLut = nullptr;
 
    friend class FSceneRenderer;
};
 
enum class ESkyAtmospherePassLocation : uint32
{
    // Renders just before the BasePass.
    BeforeBasePass,
 
    // Renders just before the PrePass but can overlap on async compute with it too.
    BeforePrePass,
};
 
// Returns the location in the frame where SkyAtmosphere is rendered.
extern ESkyAtmospherePassLocation GetSkyAtmospherePassLocation();
 
 
bool ShouldRenderSkyAtmosphere(const FScene* Scene, const FEngineShowFlags& EngineShowFlags);
 
void InitSkyAtmosphereForScene(FRHICommandListImmediate& RHICmdList, FRDGBuilder& GraphBuilder, FScene* Scene);
void InitSkyAtmosphereForView(FRHICommandListImmediate& RHICmdList, const FScene* Scene, FViewInfo& View);
 
extern void SetupSkyAtmosphereViewSharedUniformShaderParameters(const class FViewInfo& View, const FSkyAtmosphereSceneProxy& SkyAtmosphereProxy, FSkyAtmosphereViewSharedUniformShaderParameters& OutParameters);
 
// Prepare the sun light data as a function of the atmosphere state. 
void PrepareSunLightProxy(const FSkyAtmosphereRenderSceneInfo& SkyAtmosphere, uint32 AtmosphereLightIndex, FLightSceneInfo& AtmosphereLight);
 
bool IsLightAtmospherePerPixelTransmittanceEnabled(const FScene* Scene, const FViewInfo& View, const FLightSceneInfo* const LightSceneInfo);
 
float GetValidAerialPerspectiveStartDepthInCm(const FViewInfo& View, const FSkyAtmosphereSceneProxy& SkyAtmosphereProxy);
 
struct SkyAtmosphereLightShadowData
{
    const FLightSceneInfo* LightVolumetricShadowSceneinfo0 = nullptr;
    const FLightSceneInfo* LightVolumetricShadowSceneinfo1 = nullptr;
    const FProjectedShadowInfo* ProjectedShadowInfo0 = nullptr;
    const FProjectedShadowInfo* ProjectedShadowInfo1 = nullptr;
    int VirtualShadowMapId0 = INDEX_NONE;
    int VirtualShadowMapId1 = INDEX_NONE;
};
bool ShouldSkySampleAtmosphereLightsOpaqueShadow(const FScene& Scene, const TArray<FVisibleLightInfo, SceneRenderingAllocator>& VisibleLightInfos, SkyAtmosphereLightShadowData& LightShadowData);
void GetSkyAtmosphereLightsUniformBuffers(
    FRDGBuilder& GraphBuilder,
    TRDGUniformBufferRef<FVolumeShadowingShaderParametersGlobal0>& OutLightShadowShaderParams0UniformBuffer,
    TRDGUniformBufferRef<FVolumeShadowingShaderParametersGlobal1>& OutLightShadowShaderParams1UniformBuffer,
    const SkyAtmosphereLightShadowData& LightShadowData,
    const FViewInfo& ViewInfo,
    const bool bShouldSampleOpaqueShadow,
    const EUniformBufferUsage UniformBufferUsage);
 
 
bool ShouldRenderSkyAtmosphereDebugPasses(const FScene* Scene, const FEngineShowFlags& EngineShowFlags);
FScreenPassTexture AddSkyAtmosphereDebugPasses(FRDGBuilder& GraphBuilder, FScene* Scene, const FSceneViewFamily& ViewFamily, const FViewInfo& View, FScreenPassTexture& ScreenPassSceneColor);