Avoid building the mip chain a second time for SSR for transparent objects. (#93)

* - Avoid building the mip chain a second time for SSR for transparent objects.

* Update ScreenSpaceReflections.compute

* fix merge issue

Co-authored-by: sebastienlagarde <[email protected]>

Author: anisunity

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -661,6 +661,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Raytracing: Removed the dynamic lightmap multicompile.
 - Raytracing: Remove the LOD cross fade multi compile for ray tracing.
 - Cookie are now supported in lightmaper. All lights casting cookie and baked will now include cookie influence.
+- Avoid building the mip chain a second time for SSR for transparent objects.
 
 ## [7.1.1] - 2019-09-05
 

com.unity.render-pipelines.high-definition/Runtime/Lighting/ScreenSpaceLighting/ScreenSpaceReflections.compute

@@ -8,6 +8,8 @@
 #pragma kernel ScreenSpaceReflectionsTracing      SSR_TRACE
 #pragma kernel ScreenSpaceReflectionsReprojection SSR_REPROJECT
 
+#pragma multi_compile _ DEPTH_SOURCE_NOT_FROM_MIP_CHAIN
+
 // Tweak parameters.
 // #define DEBUG
 #define SSR_TRACE_BEHIND_OBJECTS
@@ -41,6 +43,20 @@
     RW_TEXTURE2D(float4, _SsrDebugTexture);
 #endif
 
+// For opaque we do the following operation:
+// - Render opaque object in depth buffer
+// - Generate depth pyramid from opaque depth buffer
+// - Trigger ray from position recover from depth pyramid and raymarch with depth pyramid
+// For transparent reflection we chose to not regenerate a depth pyramid to save performance. So we have
+// - Generate depth pyramid from opaque depth buffer
+// - Trigger ray from position recover from depth buffer (use depth pyramid) and raymarch with depth pyramid
+// - Render transparent object with reflection in depth buffer in transparent prepass
+// - Trigger ray from position recover from new depth buffer and raymarch with opaque depth pyramid
+// So we need a seperate texture for the mip chain and for the depth source when doing the transprent reflection
+#ifdef DEPTH_SOURCE_NOT_FROM_MIP_CHAIN
+TEXTURE2D_X(_DepthTexture);
+#endif
+
 #ifdef SSR_TRACE
     TEXTURE2D_X_UINT2(         _StencilTexture);
     RW_TEXTURE2D_X(float2, _SsrHitPointTexture);
@@ -104,7 +120,12 @@ void ScreenSpaceReflectionsTracing(uint3 groupId          : SV_GroupID,
     }
 
     float2 positionNDC = positionSS * _ScreenSize.zw + (0.5 * _ScreenSize.zw); // Should we precompute the half-texel bias? We seem to use it a lot.
+
+#ifdef DEPTH_SOURCE_NOT_FROM_MIP_CHAIN
+    float  deviceDepth = LOAD_TEXTURE2D_X(_DepthTexture, positionSS).r;
+#else
     float  deviceDepth = LOAD_TEXTURE2D_X(_CameraDepthTexture, positionSS).r;
+#endif
 
     bool killRay = deviceDepth == UNITY_RAW_FAR_CLIP_VALUE;
 

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

@@ -244,6 +244,7 @@ LightingOutput RenderDeferredLighting(  RenderGraph                 renderGraph,
         class RenderSSRPassData
         {
             public RenderSSRParameters parameters;
+            public TextureHandle depthBuffer;
             public TextureHandle depthPyramid;
             public TextureHandle colorPyramid;
             public TextureHandle stencilBuffer;
@@ -257,6 +258,7 @@ TextureHandle RenderSSR(    RenderGraph     renderGraph,
                                     HDCamera        hdCamera,
                                     TextureHandle   normalBuffer,
                                     TextureHandle   motionVectorsBuffer,
+                                    TextureHandle   depthBuffer,
                                     TextureHandle   depthPyramid,
                                     TextureHandle   stencilBuffer,
                                     TextureHandle   clearCoatMask)
@@ -285,7 +287,8 @@ TextureHandle RenderSSR(    RenderGraph     renderGraph,
 
                     var colorPyramid = renderGraph.ImportTexture(hdCamera.GetPreviousFrameRT((int)HDCameraFrameHistoryType.ColorBufferMipChain));
 
-                    passData.parameters = PrepareSSRParameters(hdCamera, m_DepthBufferMipChainInfo);
+                    passData.parameters = PrepareSSRParameters(hdCamera, m_DepthBufferMipChainInfo, true);
+                    passData.depthBuffer = builder.ReadTexture(depthBuffer);
                     passData.depthPyramid = builder.ReadTexture(depthPyramid);
                     passData.colorPyramid = builder.ReadTexture(colorPyramid);
                     passData.stencilBuffer = builder.ReadTexture(stencilBuffer);
@@ -308,6 +311,7 @@ TextureHandle RenderSSR(    RenderGraph     renderGraph,
                     {
                         var res = context.resources;
                         RenderSSR(data.parameters,
+                                    res.GetTexture(data.depthBuffer),
                                     res.GetTexture(data.depthPyramid),
                                     res.GetTexture(data.hitPointsTexture),
                                     res.GetTexture(data.stencilBuffer),

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

@@ -75,6 +75,7 @@ void ExecuteWithRenderGraph(    RenderRequest           renderRequest,
                                                               hdCamera,
                                                               prepassOutput.resolvedNormalBuffer,
                                                               prepassOutput.resolvedMotionVectorsBuffer,
+                                                              prepassOutput.depthBuffer,
                                                               prepassOutput.depthPyramidTexture,
                                                               prepassOutput.stencilBuffer,
                                                               clearCoatMask);

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

@@ -3878,6 +3878,7 @@ struct RenderSSRParameters
             public ComputeShader    ssrCS;
             public int              tracingKernel;
             public int              reprojectionKernel;
+            public bool             transparentSSR;
 
             public int              width, height, viewCount;
 
@@ -3887,14 +3888,15 @@ struct RenderSSRParameters
             public ShaderVariablesScreenSpaceReflection cb;
         }
 
-        RenderSSRParameters PrepareSSRParameters(HDCamera hdCamera, in HDUtils.PackedMipChainInfo depthPyramid)
+        RenderSSRParameters PrepareSSRParameters(HDCamera hdCamera, in HDUtils.PackedMipChainInfo depthPyramid, bool transparentSSR)
         {
             var volumeSettings = hdCamera.volumeStack.GetComponent<ScreenSpaceReflection>();
             var parameters = new RenderSSRParameters();
 
             parameters.ssrCS = m_ScreenSpaceReflectionsCS;
             parameters.tracingKernel = m_SsrTracingKernel;
             parameters.reprojectionKernel = m_SsrReprojectionKernel;
+            parameters.transparentSSR = transparentSSR;
 
             parameters.width = hdCamera.actualWidth;
             parameters.height = hdCamera.actualHeight;
@@ -3927,6 +3929,7 @@ RenderSSRParameters PrepareSSRParameters(HDCamera hdCamera, in HDUtils.PackedMip
         }
 
         static void RenderSSR(  in RenderSSRParameters  parameters,
+                                RTHandle                depthTexture,
                                 RTHandle                depthPyramid,
                                 RTHandle                SsrHitPointTexture,
                                 RTHandle                stencilBuffer,
@@ -3941,6 +3944,12 @@ static void RenderSSR(  in RenderSSRParameters  parameters,
             using (new ProfilingScope(cmd, ProfilingSampler.Get(HDProfileId.SsrTracing)))
             {
                 // cmd.SetComputeTextureParam(cs, kernel, "_SsrDebugTexture",    m_SsrDebugTexture);
+                // Bind the non mip chain if we are rendering the transaprent version
+                if (parameters.transparentSSR)
+                {
+                    CoreUtils.SetKeyword(cmd, "DEPTH_SOURCE_NOT_FROM_MIP_CHAIN", true);
+                    cmd.SetComputeTextureParam(cs, parameters.tracingKernel, HDShaderIDs._DepthTexture, depthTexture);
+                }
                 cmd.SetComputeTextureParam(cs, parameters.tracingKernel, HDShaderIDs._CameraDepthTexture, depthPyramid);
                 cmd.SetComputeTextureParam(cs, parameters.tracingKernel, HDShaderIDs._SsrClearCoatMaskTexture, clearCoatMask);
                 cmd.SetComputeTextureParam(cs, parameters.tracingKernel, HDShaderIDs._SsrHitPointTexture, SsrHitPointTexture);
@@ -3960,6 +3969,9 @@ static void RenderSSR(  in RenderSSRParameters  parameters,
                 ConstantBuffer.Push(cmd, parameters.cb, cs, HDShaderIDs._ShaderVariablesScreenSpaceReflection);
 
                 cmd.DispatchCompute(cs, parameters.tracingKernel, HDUtils.DivRoundUp(parameters.width, 8), HDUtils.DivRoundUp(parameters.height, 8), parameters.viewCount);
+
+                if (parameters.transparentSSR)
+                    CoreUtils.SetKeyword(cmd, "DEPTH_SOURCE_NOT_FROM_MIP_CHAIN", false);
             }
 
             using (new ProfilingScope(cmd, ProfilingSampler.Get(HDProfileId.SsrReprojection)))
@@ -3997,8 +4009,8 @@ void RenderSSR(HDCamera hdCamera, CommandBuffer cmd, ScriptableRenderContext ren
                 // Evaluate the clear coat mask texture based on the lit shader mode
                 RTHandle clearCoatMask = hdCamera.frameSettings.litShaderMode == LitShaderMode.Deferred ? m_GbufferManager.GetBuffer(2) : TextureXR.GetBlackTexture();
 
-                var parameters = PrepareSSRParameters(hdCamera, m_SharedRTManager.GetDepthBufferMipChainInfo());
-                RenderSSR(parameters, m_SharedRTManager.GetDepthTexture(), m_SsrHitPointTexture,
+                var parameters = PrepareSSRParameters(hdCamera, m_SharedRTManager.GetDepthBufferMipChainInfo(), false);
+                RenderSSR(parameters, m_SharedRTManager.GetDepthStencilBuffer(), m_SharedRTManager.GetDepthTexture(), m_SsrHitPointTexture,
                           m_SharedRTManager.GetStencilBuffer(hdCamera.frameSettings.IsEnabled(FrameSettingsField.MSAA)), clearCoatMask, previousColorPyramid,
                           m_SsrLightingTexture, cmd, renderContext);
 
@@ -4027,16 +4039,12 @@ void RenderSSRTransparent(HDCamera hdCamera, CommandBuffer cmd, ScriptableRender
                 // Clear the SSR lighting buffer (not sure it is required)
                 CoreUtils.SetRenderTarget(cmd, m_SsrLightingTexture, ClearFlag.Color, Color.clear);
                 CoreUtils.SetRenderTarget(cmd, m_SsrHitPointTexture, ClearFlag.Color, Color.clear);
-
-                // Invalid the depth pyramid and regenerate the depth pyramid
-                m_IsDepthBufferCopyValid = false;
-                GenerateDepthPyramid(hdCamera, cmd, FullScreenDebugMode.DepthPyramid);
             }
 
             // Evaluate the screen space reflection for the transparent pixels
             var previousColorPyramid = hdCamera.GetPreviousFrameRT((int)HDCameraFrameHistoryType.ColorBufferMipChain);
-            var parameters = PrepareSSRParameters(hdCamera, m_SharedRTManager.GetDepthBufferMipChainInfo());
-            RenderSSR(parameters, m_SharedRTManager.GetDepthTexture(), m_SsrHitPointTexture, m_SharedRTManager.GetStencilBuffer(), TextureXR.GetBlackTexture(), previousColorPyramid, m_SsrLightingTexture, cmd, renderContext);
+            var parameters = PrepareSSRParameters(hdCamera, m_SharedRTManager.GetDepthBufferMipChainInfo(), true);
+            RenderSSR(parameters, m_SharedRTManager.GetDepthStencilBuffer(), m_SharedRTManager.GetDepthTexture(), m_SsrHitPointTexture, m_SharedRTManager.GetStencilBuffer(), TextureXR.GetBlackTexture(), previousColorPyramid, m_SsrLightingTexture, cmd, renderContext);
 
             // If color pyramid was not valid, we bind a black texture
             if (!hdCamera.colorPyramidHistoryIsValid)