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Source/Engine/Renderer/VolumetricFogPass.h

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+// Copyright (c) 2012-2020 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#include "Engine/Graphics/RenderView.h"
+#include "Engine/Graphics/GPUPipelineStatePermutations.h"
+#include "RendererPass.h"
+
+/// <summary>
+/// Volumetric fog rendering service.
+/// </summary>
+class VolumetricFogPass : public RendererPass<VolumetricFogPass>
+{
+private:
+
+    PACK_STRUCT(struct SkyLightData {
+        Vector3 MultiplyColor;
+        float VolumetricScatteringIntensity;
+        Vector3 AdditiveColor;
+        float Dummt0;
+        });
+
+    PACK_STRUCT(struct Data {
+        GBufferData GBuffer;
+
+        Vector3 GlobalAlbedo;
+        float GlobalExtinctionScale;
+
+        Vector3 GlobalEmissive;
+        float HistoryWeight;
+
+        Vector3 GridSize;
+        uint32 HistoryMissSuperSampleCount;
+
+        int32 GridSizeIntX;
+        int32 GridSizeIntY;
+        int32 GridSizeIntZ;
+        float PhaseG;
+
+        Vector2 Dummy0;
+        float VolumetricFogMaxDistance;
+        float InverseSquaredLightDistanceBiasScale;
+
+        Vector4 FogParameters;
+
+        Matrix PrevWorldToClip;
+
+        Vector4 FrameJitterOffsets[8];
+
+        LightData DirectionalLight;
+        LightShadowData DirectionalLightShadow;
+        SkyLightData SkyLight;
+        });
+
+    PACK_STRUCT(struct PerLight {
+        Vector2 Dummy1;
+        int32 MinZ;
+        float LocalLightScatteringIntensity;
+
+        Vector4 ViewSpaceBoundingSphere;
+        Matrix ViewToVolumeClip;
+
+        LightData LocalLight;
+        LightShadowData LocalLightShadow;
+        });
+
+    // Shader stuff
+    AssetReference<Shader> _shader;
+    GPUShaderProgramCS* _csInitialize = nullptr;
+    ComputeShaderPermutation<2> _csLightScattering;
+    GPUShaderProgramCS* _csFinalIntegration = nullptr;
+    GPUPipelineStatePermutationsPs<4> _psInjectLight;
+
+    GPUBuffer* _vbCircleRasterize = nullptr;
+    GPUBuffer* _ibCircleRasterize = nullptr;
+
+    /// <summary>
+    /// The current frame cache (initialized during Init)
+    /// </summary>
+    struct FrameCache
+    {
+        /// <summary>
+        /// The XY size of a cell in the voxel grid, in pixels.
+        /// </summary>
+        int32 GridPixelSize;
+
+        /// <summary>
+        /// How many Volumetric Fog cells to use in z (depth from camera).
+        /// </summary>
+        int32 GridSizeZ;
+
+        /// <summary>
+        ///  Whether to apply jitter to each frame's volumetric fog. Should be used with temporal reprojection to improve the quality.
+        /// </summary>
+        bool FogJitter;
+
+        /// <summary>
+        /// Whether to use temporal reprojection on volumetric fog.
+        /// </summary>
+        bool TemporalReprojection;
+
+        /// <summary>
+        /// How much the history value should be weighted each frame. This is a tradeoff between visible jittering and responsiveness.
+        /// </summary>
+        float HistoryWeight;
+
+        /// <summary>
+        /// Number of lighting samples to compute for voxels whose history value is not available. This reduces noise when panning or on camera cuts, but introduces a variable cost to volumetric fog computation. Valid range [1, 8].
+        /// </summary>
+        int32 HistoryMissSupersampleCount;
+
+        /// <summary>
+        /// Scales the amount added to the inverse squared falloff denominator. This effectively removes the spike from inverse squared falloff that causes extreme aliasing.
+        /// </summary>
+        float InverseSquaredLightDistanceBiasScale;
+
+        /// <summary>
+        /// The calculated size of the volume texture.
+        /// </summary>
+        Vector3 GridSize;
+
+        /// <summary>
+        /// The cached per-frame data for the constant buffer.
+        /// </summary>
+        Data Data;
+    };
+
+    FrameCache _cache;
+    bool _isSupported;
+
+public:
+
+    /// <summary>
+    /// Init
+    /// </summary>
+    VolumetricFogPass();
+
+public:
+
+    /// <summary>
+    /// Renders the light to the volumetric fog light scattering volume texture. Called by the light pass after shadow map rendering. Used by the shadows casting lights.
+    /// </summary>
+    /// <param name="renderContext">The rendering context.</param>
+    /// <param name="context">The GPU commands context.</param>
+    /// <param name="light">The light.</param>
+    /// <param name="shadowMap">The shadow map.</param>
+    /// <param name="shadow">The light shadow data.</param>
+    void RenderLight(RenderContext& renderContext, GPUContext* context, RendererPointLightData& light, GPUTextureView* shadowMap, LightShadowData& shadow);
+
+    /// <summary>
+    /// Renders the light to the volumetric fog light scattering volume texture. Called by the light pass after shadow map rendering. Used by the shadows casting lights.
+    /// </summary>
+    /// <param name="renderContext">The rendering context.</param>
+    /// <param name="context">The GPU commands context.</param>
+    /// <param name="light">The light.</param>
+    /// <param name="shadowMap">The shadow map.</param>
+    /// <param name="shadow">The light shadow data.</param>
+    void RenderLight(RenderContext& renderContext, GPUContext* context, RendererSpotLightData& light, GPUTextureView* shadowMap, LightShadowData& shadow);
+
+    /// <summary>
+    /// Renders the volumetric fog (generates integrated light scattering 3D texture). Does nothing if feature is disabled or not supported.
+    /// </summary>
+    /// <param name="renderContext">The rendering context.</param>
+    void Render(RenderContext& renderContext);
+
+private:
+
+    bool Init(RenderContext& renderContext, GPUContext* context, VolumetricFogOptions& options);
+    GPUTextureView* GetLocalShadowedLightScattering(RenderContext& renderContext, GPUContext* context, VolumetricFogOptions& options) const;
+    void InitCircleRasterizeBuffers();
+    template<typename T>
+    void RenderRadialLight(RenderContext& renderContext, GPUContext* context, T& light, LightShadowData& shadow);
+    template<typename T>
+    void RenderRadialLight(RenderContext& renderContext, GPUContext* context, RenderView& view, VolumetricFogOptions& options, T& light, PerLight& perLight, GPUConstantBuffer* cb1);
+#if COMPILE_WITH_DEV_ENV
+    void OnShaderReloading(Asset* obj)
+    {
+        _psInjectLight.Release();
+        _csInitialize = nullptr;
+        _csLightScattering.Clear();
+        _csFinalIntegration = nullptr;
+        invalidateResources();
+    }
+#endif
+
+public:
+
+    // [RendererPass]
+    String ToString() const override;
+    bool Init() override;
+    void Dispose() override;
+
+protected:
+
+    // [RendererPass]
+    bool setupResources() override;
+};