Fixed SSAO on DX11

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightConstantBuffer.cs

         public static int _AdditionalLightSpotDir;
         public static int _AdditionalLightSpotAttenuation;
 
-        public static int _AmbientOcclusionBuffer;
         public static int _AmbientOcclusionParam;
     }
 

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

         private int m_ShadowCasterCascadesCount;
         private int m_ShadowMapRTID;
         private int m_ScreenSpaceShadowMapRTID;
+        private int m_AmbientOcclusionRTID;
+        private RenderTargetIdentifier m_AmbientOcclusionRT;
-
-        private RTHandle m_AmbientOcclusionBuffer;
 
         private bool m_IntermediateTextureArray;
         private bool m_RequireDepthTexture;
             PerCameraBuffer._AdditionalLightDistanceAttenuation = Shader.PropertyToID("_AdditionalLightDistanceAttenuation");
             PerCameraBuffer._AdditionalLightSpotDir = Shader.PropertyToID("_AdditionalLightSpotDir");
             PerCameraBuffer._AdditionalLightSpotAttenuation = Shader.PropertyToID("_AdditionalLightSpotAttenuation");
-            PerCameraBuffer._AmbientOcclusionBuffer = Shader.PropertyToID("_AmbientOcclusion");
             PerCameraBuffer._AmbientOcclusionParam = Shader.PropertyToID("_AmbientOcclusionParam");
 
             ShadowConstantBuffer._WorldToShadow = Shader.PropertyToID("_WorldToShadow");
 
             m_ShadowMapRTID = Shader.PropertyToID("_ShadowMap");
             m_ScreenSpaceShadowMapRTID = Shader.PropertyToID("_ScreenSpaceShadowMap");
+            m_AmbientOcclusionRTID = Shader.PropertyToID("_AmbientOcclusion");
 
             CameraRenderTargetID.color = Shader.PropertyToID("_CameraColorRT");
             CameraRenderTargetID.copyColor = Shader.PropertyToID("_CameraCopyColorRT");
             m_ShadowMapRT = new RenderTargetIdentifier(m_ShadowMapRTID);
             m_ScreenSpaceShadowMapRT = new RenderTargetIdentifier(m_ScreenSpaceShadowMapRTID);
+            m_AmbientOcclusionRT = new RenderTargetIdentifier(m_AmbientOcclusionRTID);
             
             m_ColorRT = new RenderTargetIdentifier(CameraRenderTargetID.color);
             m_CopyColorRT = new RenderTargetIdentifier(CameraRenderTargetID.copyColor);
 
-            RTHandle.Initialize(Screen.width, Screen.height, false, (MSAASamples)m_Asset.MSAASampleCount);
-            m_AmbientOcclusionBuffer = RTHandle.Alloc(Vector2.one, filterMode: FilterMode.Bilinear, colorFormat: RenderTextureFormat.R8, sRGB: false, enableRandomWrite: true, name: "AmbientOcclusion");
-
             m_CopyTextureSupport = SystemInfo.copyTextureSupport;
 
             for (int i = 0; i < kMaxCascades; ++i)
         {
             base.Dispose();
             Shader.globalRenderPipeline = "";
-
-            RTHandle.Release(m_AmbientOcclusionBuffer);
 
             SupportedRenderingFeatures.active = new SupportedRenderingFeatures();
 
 #endif
                 cmd.ReleaseTemporaryRT(m_ShadowMapRTID);
                 cmd.ReleaseTemporaryRT(m_ScreenSpaceShadowMapRTID);
-                cmd.ReleaseTemporaryRT(PerCameraBuffer._AmbientOcclusionBuffer);
+                cmd.ReleaseTemporaryRT(m_AmbientOcclusionRTID);
                 cmd.ReleaseTemporaryRT(CameraRenderTargetID.depthCopy);
                 cmd.ReleaseTemporaryRT(CameraRenderTargetID.depth);
                 cmd.ReleaseTemporaryRT(CameraRenderTargetID.color);
                 var settings = postProcessLayer.GetSettings<AmbientOcclusion>();
                 if(settings.IsEnabledAndSupported(null))
                 {
+                    //NOTE: On DX11, need to manually specify random read write for the compute UAV.
+                    cmd.GetTemporaryRT(m_AmbientOcclusionRTID, m_CurrCamera.pixelWidth, m_CurrCamera.pixelHeight, 0, FilterMode.Bilinear, RenderTextureFormat.R8, RenderTextureReadWrite.Linear, 1, true);
+
-                    postProcessLayer.BakeMSVOMap(cmd, camera, m_AmbientOcclusionBuffer, m_DepthRT, true);
+                    postProcessLayer.BakeMSVOMap(cmd, camera, m_AmbientOcclusionRT, m_DepthRT, true);
-                    cmd.SetGlobalTexture(PerCameraBuffer._AmbientOcclusionBuffer, m_AmbientOcclusionBuffer);
+                    cmd.SetGlobalTexture(m_AmbientOcclusionRTID, m_AmbientOcclusionRT);
                     cmd.SetGlobalVector(PerCameraBuffer._AmbientOcclusionParam, new Vector4(settings.color.value.r, 
                                                                                             settings.color.value.g, 
                                                                                             settings.color.value.b, 
                 }
             }
 
-            cmd.SetGlobalTexture(PerCameraBuffer._AmbientOcclusionBuffer, RuntimeUtilities.blackTexture);
+            cmd.SetGlobalTexture(m_AmbientOcclusionRTID, RuntimeUtilities.blackTexture);
             cmd.SetGlobalVector(PerCameraBuffer._AmbientOcclusionParam, Vector4.zero);
 
             context.ExecuteCommandBuffer(cmd);