Higt res env on camera misses, render sky only on first accum frame.

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Accumulation/Shaders/Accumulation.compute

@@ -4,11 +4,11 @@
 
 #pragma kernel KMain
 
-#pragma multi_compile _ INPUT_FROM_RADIANCE_TEXTURE
+#pragma multi_compile _ INPUT_FROM_FRAME_TEXTURE
 
 // Inputs
-#ifdef INPUT_FROM_RADIANCE_TEXTURE
-TEXTURE2D_X(_RadianceTexture);
+#ifdef INPUT_FROM_FRAME_TEXTURE
+TEXTURE2D_X(_FrameTexture);
 #endif
 
 float4      _AccumulationWeights;
@@ -55,25 +55,18 @@ void KMain(uint3 dispatchThreadId : SV_DispatchThreadID)
     exposureMultiplier.xyz = (_AccumulationNeedsExposure != 0) ? GetCurrentExposureMultiplier() : 1.0;
     exposureMultiplier.w = 1.0;
 
-#ifdef INPUT_FROM_RADIANCE_TEXTURE
-        float4 color, colorBg = _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)];
-#else
-        float4 color, colorBg = 0.0;
-#endif
-
     // Have we reached max sampling?
     uint sampleCount = _AccumulationFrameIndex;
     if (sampleCount >= _AccumulationNumSamples)
     {
-        color = _AccumulatedFrameTexture[COORD_TEXTURE2D_X(currentPixelCoord)] * exposureMultiplier;
-        _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)] = color + (1.0 - color.w) * colorBg;
+        _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)] = _AccumulatedFrameTexture[COORD_TEXTURE2D_X(currentPixelCoord)] * exposureMultiplier;
     }
     else
     {
-#ifdef INPUT_FROM_RADIANCE_TEXTURE
-        color = _RadianceTexture[COORD_TEXTURE2D_X(currentPixelCoord)];
+#ifdef INPUT_FROM_FRAME_TEXTURE
+        float4 color = _FrameTexture[COORD_TEXTURE2D_X(dispatchThreadId.xy)];
 #else
-        color = _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)];
+        float4 color = _CameraColorTextureRW[COORD_TEXTURE2D_X(dispatchThreadId.xy)];
 #endif
 
         if (sampleCount++)
@@ -87,6 +80,6 @@ void KMain(uint3 dispatchThreadId : SV_DispatchThreadID)
         // Add a little convergence cue to our result
         AddConvergenceCue(currentPixelCoord, sampleCount, color.xyz);
 
-        _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)] = color + (1.0 - color.w) * colorBg;
+        _CameraColorTextureRW[COORD_TEXTURE2D_X(currentPixelCoord)] = color;
     }
 }

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Accumulation/SubFrameManager.cs

@@ -286,7 +286,7 @@ RenderAccumulationParameters PrepareRenderAccumulationParameters(HDCamera hdCame
             parameters.accumulationCS.shaderKeywords = null;
             if (inputFromRadianceTexture)
             {
-                parameters.accumulationCS.EnableKeyword("INPUT_FROM_RADIANCE_TEXTURE");
+                parameters.accumulationCS.EnableKeyword("INPUT_FROM_FRAME_TEXTURE");
             }
             return parameters;
         }
@@ -311,7 +311,7 @@ static void RenderAccumulation(in RenderAccumulationParameters parameters, RTHan
             cmd.SetComputeTextureParam(accumulationShader, parameters.accumulationKernel, HDShaderIDs._CameraColorTextureRW, outputTexture);
             if (!inputTexture.Equals(outputTexture))
             {
-                cmd.SetComputeTextureParam(accumulationShader, parameters.accumulationKernel, HDShaderIDs._RadianceTexture, inputTexture);
+                cmd.SetComputeTextureParam(accumulationShader, parameters.accumulationKernel, HDShaderIDs._FrameTexture, inputTexture);
             }
             cmd.SetComputeVectorParam(accumulationShader, HDShaderIDs._AccumulationWeights, frameWeights);
             cmd.SetComputeIntParam(accumulationShader, HDShaderIDs._AccumulationNeedsExposure, parameters.needExposure ? 1 : 0);

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDRenderPipeline.RenderGraph.cs

@@ -93,8 +93,6 @@ void ExecuteWithRenderGraph(RenderRequest           renderRequest,
 
                 if (hdCamera.viewCount == 1)
                 {
-                    var clearDepthBuffer = CreateDepthBuffer(m_RenderGraph, true, false);
-                    RenderSky(m_RenderGraph, hdCamera, colorBuffer, colorBuffer, clearDepthBuffer, clearDepthBuffer, false);
                     colorBuffer = RenderPathTracing(m_RenderGraph, hdCamera, colorBuffer);
                 }
                 else
@@ -1147,7 +1145,7 @@ class RenderSkyPassData
             public SkyManager           skyManager;
         }
 
-        void RenderSky(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle colorBuffer, TextureHandle volumetricLighting, TextureHandle depthStencilBuffer, TextureHandle depthTexture, bool computeFog = true)
+        void RenderSky(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle colorBuffer, TextureHandle volumetricLighting, TextureHandle depthStencilBuffer, TextureHandle depthTexture)
         {
             if (m_CurrentDebugDisplaySettings.DebugHideSky(hdCamera))
                 return;
@@ -1173,7 +1171,7 @@ void RenderSky(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle colorBu
                         // Then we perform a copy from the atmospheric scattering buffer back to the color buffer.
                         data.skyManager.RenderSky(data.hdCamera, data.sunLight, data.colorBuffer, data.depthStencilBuffer, data.debugDisplaySettings, context.cmd);
 
-                        if (computeFog && Fog.IsFogEnabled(data.hdCamera) || Fog.IsPBRFogEnabled(data.hdCamera))
+                        if (Fog.IsFogEnabled(data.hdCamera) || Fog.IsPBRFogEnabled(data.hdCamera))
                         {
                             var pixelCoordToViewDirWS = data.hdCamera.mainViewConstants.pixelCoordToViewDirWS;
                             data.skyManager.RenderOpaqueAtmosphericScattering(context.cmd, data.hdCamera, data.colorBuffer, data.depthTexture, data.volumetricLighting, data.intermediateBuffer, data.depthStencilBuffer, pixelCoordToViewDirWS, data.hdCamera.frameSettings.IsEnabled(FrameSettingsField.MSAA));

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDStringConstants.cs

@@ -685,12 +685,13 @@ static class HDShaderIDs
         public static readonly int _SubSurfaceLightingBuffer        = Shader.PropertyToID("_SubSurfaceLightingBuffer");
         public static readonly int _IndirectDiffuseLightingBuffer   = Shader.PropertyToID("_IndirectDiffuseLightingBuffer");
 
-        // Accumulation
+        // Accumulation and path tracing
         public static readonly int _AccumulationFrameIndex          = Shader.PropertyToID("_AccumulationFrameIndex");
         public static readonly int _AccumulationNumSamples          = Shader.PropertyToID("_AccumulationNumSamples");
         public static readonly int _AccumulationWeights             = Shader.PropertyToID("_AccumulationWeights");
         public static readonly int _AccumulationNeedsExposure       = Shader.PropertyToID("_AccumulationNeedsExposure");
-        public static readonly int _RadianceTexture                 = Shader.PropertyToID("_RadianceTexture");
+        public static readonly int _FrameTexture                    = Shader.PropertyToID("_FrameTexture");
+        public static readonly int _SkyCameraTexture                = Shader.PropertyToID("_SkyCameraTexture");
 
         // Preintegrated texture name
         public static readonly int _PreIntegratedFGD_GGXDisneyDiffuse = Shader.PropertyToID("_PreIntegratedFGD_GGXDisneyDiffuse");

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/PathTracing/PathTracing.cs

@@ -69,8 +69,10 @@ public partial class HDRenderPipeline
 #endif // UNITY_EDITOR
         ulong m_CacheAccelSize = 0;
         uint  m_CacheLightCount = 0;
+        bool  m_RenderSky = true;
 
-        TextureHandle m_RadianceTexture; // stores the per-pixel results of path tracing for this frame
+        TextureHandle m_FrameTexture; // stores the per-pixel results of path tracing for one frame
+        TextureHandle m_SkyTexture; // stores the sky background
 
         void InitPathTracing(RenderGraph renderGraph)
         {
@@ -80,14 +82,18 @@ void InitPathTracing(RenderGraph renderGraph)
             SceneView.duringSceneGui += OnSceneGui;
 #endif // UNITY_EDITOR
 
-            TextureDesc radianceTextureDesc = new TextureDesc(Vector2.one, true, true);
-            radianceTextureDesc.colorFormat = GraphicsFormat.R32G32B32A32_SFloat;           
-            radianceTextureDesc.enableRandomWrite = true;
-            radianceTextureDesc.useMipMap = false;
-            radianceTextureDesc.autoGenerateMips = false;
-            radianceTextureDesc.name = "PathTracingFrameBuffer";
+            TextureDesc td = new TextureDesc(Vector2.one, true, true);
+            td.colorFormat = GraphicsFormat.R32G32B32A32_SFloat;
+            td.useMipMap = false;
+            td.autoGenerateMips = false;
 
-            m_RadianceTexture = renderGraph.CreateSharedTexture(radianceTextureDesc);
+            td.name = "PathTracingFrameBuffer";
+            td.enableRandomWrite = true;
+            m_FrameTexture = renderGraph.CreateSharedTexture(td);
+
+            td.name = "PathTracingSkyBuffer";
+            td.enableRandomWrite = false;
+            m_SkyTexture = renderGraph.CreateSharedTexture(td);
         }
 
         void ReleasePathTracing()
@@ -101,9 +107,17 @@ void ReleasePathTracing()
 
         internal void ResetPathTracing()
         {
+            m_RenderSky = true;
             m_SubFrameManager.Reset();
         }
 
+        internal void ResetPathTracing(int camID, CameraData camData)
+        {
+            m_RenderSky = true;
+            camData.ResetIteration();
+            m_SubFrameManager.SetCameraData(camID, camData);
+        }
+
         private Vector4 ComputeDoFConstants(HDCamera hdCamera, PathTracing settings)
         {
             var dofSettings = hdCamera.volumeStack.GetComponent<DepthOfField>();
@@ -122,6 +136,7 @@ private void OnSceneEdit()
             // If we just change the sample count, we don't necessarily want to reset iteration
             if (m_PathTracingSettings && m_CacheMaxIteration != m_PathTracingSettings.maximumSamples.value)
             {
+                m_RenderSky = true;
                 m_CacheMaxIteration = (uint)m_PathTracingSettings.maximumSamples.value;
                 m_SubFrameManager.SelectiveReset(m_CacheMaxIteration);
             }
@@ -160,8 +175,7 @@ private void CheckDirtiness(HDCamera hdCamera)
             {
                 camData.width = (uint)hdCamera.actualWidth;
                 camData.height = (uint)hdCamera.actualHeight;
-                camData.ResetIteration();
-                m_SubFrameManager.SetCameraData(camID, camData);
+                ResetPathTracing(camID, camData);
                 return;
             }
 
@@ -170,8 +184,7 @@ private void CheckDirtiness(HDCamera hdCamera)
             if (enabled != camData.skyEnabled)
             {
                 camData.skyEnabled = enabled;
-                camData.ResetIteration();
-                m_SubFrameManager.SetCameraData(camID, camData);
+                ResetPathTracing(camID, camData);
                 return;
             }
 
@@ -180,16 +193,14 @@ private void CheckDirtiness(HDCamera hdCamera)
             if (enabled != camData.fogEnabled)
             {
                 camData.fogEnabled = enabled;
-                camData.ResetIteration();
-                m_SubFrameManager.SetCameraData(camID, camData);
+                ResetPathTracing(camID, camData);
                 return;
             }
 
             // Check camera matrix dirtiness
             if (hdCamera.mainViewConstants.nonJitteredViewProjMatrix != (hdCamera.mainViewConstants.prevViewProjMatrix))
             {
-                camData.ResetIteration();
-                m_SubFrameManager.SetCameraData(camID, camData);
+                ResetPathTracing(camID, camData);
                 return;
             }
 
@@ -206,6 +217,7 @@ private void CheckDirtiness(HDCamera hdCamera)
             {
                 m_TransformDirty = false;
                 ResetPathTracing();
+                return;
             }
 
             // Check lights dirtiness
@@ -273,7 +285,7 @@ PathTracingParameters PreparePathTracingParameters(HDCamera hdCamera)
             return parameters;
         }
 
-        static void RenderPathTracing(in PathTracingParameters parameters, RTHandle radianceTexture, CommandBuffer cmd)
+        static void RenderPathTracing(in PathTracingParameters parameters, RTHandle frameTexture, RTHandle skyTexture, CommandBuffer cmd)
         {
             // Define the shader pass to use for the path tracing pass
             cmd.SetRayTracingShaderPass(parameters.pathTracingShader, "PathTracingDXR");
@@ -292,10 +304,13 @@ static void RenderPathTracing(in PathTracingParameters parameters, RTHandle radi
             cmd.SetGlobalBuffer(HDShaderIDs._LightDatasRT, parameters.lightCluster.GetLightDatas());
 
             // Set the data for the ray miss
+            cmd.SetRayTracingIntParam(parameters.pathTracingShader, HDShaderIDs._RaytracingCameraSkyEnabled, parameters.cameraData.skyEnabled ? 1 : 0);
+            cmd.SetRayTracingVectorParam(parameters.pathTracingShader, HDShaderIDs._RaytracingCameraClearColor, parameters.backgroundColor);
+            cmd.SetRayTracingTextureParam(parameters.pathTracingShader, HDShaderIDs._SkyCameraTexture, skyTexture);
             cmd.SetRayTracingTextureParam(parameters.pathTracingShader, HDShaderIDs._SkyTexture, parameters.skyReflection);
 
             // Additional data for path tracing
-            cmd.SetRayTracingTextureParam(parameters.pathTracingShader, HDShaderIDs._RadianceTexture, radianceTexture);
+            cmd.SetRayTracingTextureParam(parameters.pathTracingShader, HDShaderIDs._FrameTexture, frameTexture);
             cmd.SetRayTracingMatrixParam(parameters.pathTracingShader, HDShaderIDs._PixelCoordToViewDirWS, parameters.pixelCoordToViewDirWS);
             cmd.SetRayTracingVectorParam(parameters.pathTracingShader, HDShaderIDs._PathTracedDoFConstants, parameters.dofParameters);
 
@@ -307,25 +322,51 @@ class RenderPathTracingData
         {
             public PathTracingParameters parameters;
             public TextureHandle output;
+            public TextureHandle sky;
         }
 
-        TextureHandle RenderPathTracing(RenderGraph renderGraph, in PathTracingParameters parameters, TextureHandle pathTracingBuffer)
+        TextureHandle RenderPathTracing(RenderGraph renderGraph, in PathTracingParameters parameters, TextureHandle pathTracingBuffer, TextureHandle skyBuffer)
         {
             using (var builder = renderGraph.AddRenderPass<RenderPathTracingData>("Render PathTracing", out var passData))
             {
                 passData.parameters = parameters;
                 passData.output = builder.WriteTexture(pathTracingBuffer);
+                passData.sky = builder.ReadTexture(skyBuffer);
 
                 builder.SetRenderFunc(
                     (RenderPathTracingData data, RenderGraphContext ctx) =>
                     {
-                        RenderPathTracing(data.parameters, data.output, ctx.cmd);
+                        RenderPathTracing(data.parameters, data.output, data.sky, ctx.cmd);
                     });
 
                 return passData.output;
             }
         }
 
+        // Simpler variant used by path tracing, without depth buffer or volumetric computations
+        void RenderSky(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle skyBuffer)
+        {
+            if (m_CurrentDebugDisplaySettings.DebugHideSky(hdCamera))
+                return;
+
+            using (var builder = renderGraph.AddRenderPass<RenderSkyPassData>("Render Sky for Path Tracing", out var passData))
+            {
+                passData.visualEnvironment = hdCamera.volumeStack.GetComponent<VisualEnvironment>();
+                passData.sunLight = GetCurrentSunLight();
+                passData.hdCamera = hdCamera;
+                passData.colorBuffer = builder.WriteTexture(skyBuffer);
+                passData.depthTexture = builder.WriteTexture(CreateDepthBuffer(renderGraph, true, false));
+                passData.debugDisplaySettings = m_CurrentDebugDisplaySettings;
+                passData.skyManager = m_SkyManager;
+
+                builder.SetRenderFunc(
+                    (RenderSkyPassData data, RenderGraphContext context) =>
+                    {
+                        data.skyManager.RenderSky(data.hdCamera, data.sunLight, data.colorBuffer, passData.depthTexture, data.debugDisplaySettings, context.cmd);
+                    });
+            }
+        }
+
         TextureHandle RenderPathTracing(RenderGraph renderGraph, HDCamera hdCamera, TextureHandle colorBuffer)
         {
             RayTracingShader pathTracingShader = m_Asset.renderPipelineRayTracingResources.pathTracing;
@@ -351,10 +392,17 @@ TextureHandle RenderPathTracing(RenderGraph renderGraph, HDCamera hdCamera, Text
             var parameters = PreparePathTracingParameters(hdCamera);
             if (parameters.cameraData.currentIteration < m_SubFrameManager.subFrameCount)
             {
-                RenderPathTracing(m_RenderGraph, parameters, m_RadianceTexture);
+                // Keep a sky texture around, that we compute only on the very first frame of the accumulation
+                if (m_RenderSky)
+                {
+                    RenderSky(m_RenderGraph, hdCamera, m_SkyTexture);
+                    m_RenderSky = false;   
+                }
+
+                RenderPathTracing(m_RenderGraph, parameters, m_FrameTexture, m_SkyTexture);
             }
 
-            RenderAccumulation(m_RenderGraph, hdCamera, m_RadianceTexture, colorBuffer, true);
+            RenderAccumulation(m_RenderGraph, hdCamera, m_FrameTexture, colorBuffer, true);
 
             return colorBuffer;
         }

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/PathTracing/Shaders/PathTracingMain.raytrace

@@ -24,18 +24,23 @@
 
 // Input(s)
 float4x4 _PixelCoordToViewDirWS;
-
-// DoF related parameters
-float4   _PathTracedDoFConstants; // x: aperture radius, y: focus distance, zw: unused
+int      _RaytracingCameraSkyEnabled;
+float4   _RaytracingCameraClearColor;
+TEXTURE2D_X(_SkyCameraTexture);
 
 // Output(s)
-RWTexture2D<float4> _RadianceTexture;
+RW_TEXTURE2D_X(float4, _FrameTexture);
+
+// DoF related parameters
+float4 _PathTracedDoFConstants; // x: aperture radius, y: focus distance, zw: unused
 
 [shader("miss")]
 void MissCamera(inout PathIntersection pathIntersection : SV_RayPayload)
 {
-    pathIntersection.value = 0.0;
-    pathIntersection.alpha = 0.0;
+    bool skyEnabled = _EnvLightSkyEnabled && _RaytracingCameraSkyEnabled;
+    float4 missColor = skyEnabled ? _SkyCameraTexture[COORD_TEXTURE2D_X(pathIntersection.pixelCoord)] : _RaytracingCameraClearColor;
+    pathIntersection.value = missColor.xyz * GetInverseCurrentExposureMultiplier();
+    pathIntersection.alpha = missColor.w;
 
     ApplyFogAttenuation(WorldRayOrigin(), WorldRayDirection(), pathIntersection.value, pathIntersection.alpha);
 
@@ -146,7 +151,7 @@ void RayGen()
     // Evaluate the ray intersection
     TraceRay(_RaytracingAccelerationStructure, RAY_FLAG_CULL_BACK_FACING_TRIANGLES, RAYTRACINGRENDERERFLAG_PATH_TRACING, 0, 1, 0, rayDescriptor, pathIntersection);
 
-    _RadianceTexture[currentPixelCoord] = float4(pathIntersection.value, pathIntersection.alpha);
+    _FrameTexture[COORD_TEXTURE2D_X(currentPixelCoord)] = float4(pathIntersection.value, pathIntersection.alpha);
 }
 
 // This should never be called, return magenta just in case