Remove UAV hack from CoreUtils.UpdateRenderTextureDescriptor

Properly manage UAV + MSAA from the code that calls CreateCmdTemporaryRT

Plus some extra cleanups

ScriptableRenderPipeline/Core/CoreRP/CoreUtils.cs

             baseDesc.depthBufferBits = depthBufferBits;
             baseDesc.colorFormat = format;
             baseDesc.sRGB = (readWrite != RenderTextureReadWrite.Linear);
-            // TODO: Explicit MSAA support will come in later
-            if ((format == RenderTextureFormat.Depth) && baseDesc.msaaSamples > 1)
+            // Depth-only needs bindMS in order to use with CopyTexture
+            if ((format == RenderTextureFormat.Depth) && (baseDesc.msaaSamples > 1))
                 baseDesc.bindMS = true;
 
             return new RenderTexture(baseDesc);
             baseDesc.depthBufferBits = depthBufferBits;
             baseDesc.colorFormat = format;
             baseDesc.sRGB = (readWrite != RenderTextureReadWrite.Linear);
+
+            Debug.Assert(!enableRandomWrite || (msaaSamples == 1));
-            if (msaaSamples > 1)
-                enableRandomWrite = false;
             baseDesc.enableRandomWrite = enableRandomWrite;
         }
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Camera/HDCamera.cs

             {
                 // this is already pre-validated to be a valid sample count by InitializeFrameSettings
                 var sampleCount = QualitySettings.antiAliasing;
-                Debug.LogFormat("Quality Settings AA value: {0}", sampleCount);
-                Debug.Log("No MSAA enabled");
                 tempDesc.msaaSamples = 1;
             }
             tempDesc.depthBufferBits = 0;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

                 if (m_CameraStencilBufferCopy != null)
                     m_CameraStencilBufferCopy.Release();
 
+                // TODO: This might fail allocation with MSAA
                 m_CameraStencilBufferCopy = CoreUtils.CreateRenderTexture(hdCamera.renderTextureDesc, 0, RenderTextureFormat.R8, RenderTextureReadWrite.Linear); // DXGI_FORMAT_R8_UINT is not supported by Unity
                 m_CameraStencilBufferCopy.filterMode = FilterMode.Point;
                 m_CameraStencilBufferCopy.Create();
 
                     cmd.ReleaseTemporaryRT(m_CameraColorBuffer);
                     cmd.ReleaseTemporaryRT(m_CameraSssDiffuseLightingBuffer);
-                    CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraColorBuffer,              hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.ARGBHalf,       RenderTextureReadWrite.Linear, 0, true); // Enable UAV
-                    CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraSssDiffuseLightingBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear, 0, true); // Enable UAV
-
+                    if (m_FrameSettings.enableMSAA)
+                    {
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraColorBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.ARGBHalf, RenderTextureReadWrite.Linear);
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraSssDiffuseLightingBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear);
+                    }
+                    else
+                    {
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraColorBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.ARGBHalf, RenderTextureReadWrite.Linear, 1, true); // Enable UAV
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraSssDiffuseLightingBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear, 1, true); // Enable UAV
+                    }
 
                     // Color and depth pyramids
                     m_GaussianPyramidColorBufferDesc = BuildPyramidDescriptor(hdCamera, PyramidType.Color, m_FrameSettings.enableStereo);

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/SubsurfaceScattering/SubsurfaceScatteringManager.cs

             var desc = hdCamera.renderTextureDesc;
             desc.width = (desc.width + 7) / 8;
             desc.height = (desc.height + 7) / 8;
+            // TODO: This fails allocation with MSAA enabled?
             m_HTile = CoreUtils.CreateRenderTexture(desc, 0, RenderTextureFormat.R8, RenderTextureReadWrite.Linear); // DXGI_FORMAT_R8_UINT is not supported by Unity
             m_HTile.filterMode = FilterMode.Point;
             m_HTile.enableRandomWrite = true;
             if (sssParameters == null || !frameSettings.enableSubsurfaceScattering)
                 return;
 
+            // TODO: For MSAA, at least initially, we can only support Jimenez, because we can't
+            // create MSAA + UAV render targets.
+
             using (new ProfilingSample(cmd, "Subsurface Scattering", CustomSamplerId.SubsurfaceScattering.GetSampler()))
             {
                 // For Jimenez we always need an extra buffer, for Disney it depends on platform
                     cmd.ReleaseTemporaryRT(m_CameraFilteringBuffer);
-                    CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraFilteringBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear, 1, true); // Enable UAV
+
+                    if (frameSettings.enableMSAA)
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraFilteringBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear); // no UAV
+                    else
+                        CoreUtils.CreateCmdTemporaryRT(cmd, m_CameraFilteringBuffer, hdCamera.renderTextureDesc, 0, FilterMode.Point, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear, 1, true); // Enable UAV
 
                     // Clear the SSS filtering target
                     using (new ProfilingSample(cmd, "Clear SSS filtering target", CustomSamplerId.ClearSSSFilteringTarget.GetSampler()))