DoF: avoid calling GetDimensions for LoDs in the shader (#1256)

* DoF: Pass mipmap dimensions as shader constant

* DoF: invalidate TAA history when switching modes

Author: pmavridis

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/PostProcessSystem.cs

@@ -144,6 +144,8 @@ private enum SMAAStage
 
         HDRenderPipeline m_HDInstance;
 
+        bool m_IsDoFHisotoryValid = false;
+
         void FillEmptyExposureTexture()
         {
             var tex = new Texture2D(1, 1, TextureFormat.RGHalf, false, true);
@@ -615,6 +617,12 @@ void PoolSource(ref RTHandle src, RTHandle dst)
                     {
                         using (new ProfilingScope(cmd, ProfilingSampler.Get(HDProfileId.DepthOfField)))
                         {
+                            // If we switch DoF modes and the old one was not using TAA, make sure we invalidate the history 
+                            if (taaEnabled && m_IsDoFHisotoryValid != m_DepthOfField.physicallyBased)
+                            {
+                                camera.resetPostProcessingHistory = true;
+                            }
+
                             var destination = m_Pool.Get(Vector2.one, m_ColorFormat);
                             if (!m_DepthOfField.physicallyBased)
                                 DoDepthOfField(cmd, camera, source, destination, taaEnabled);
@@ -634,6 +642,8 @@ void PoolSource(ref RTHandle src, RTHandle dst)
                                 PoolSource(ref source, taaDestination);
                                 postDoFTAAEnabled = true;
                             }
+
+                            m_IsDoFHisotoryValid = (m_DepthOfField.physicallyBased && taaEnabled);
                         }
                     }
 
@@ -2279,6 +2289,20 @@ void ReprojectCoCHistory(CommandBuffer cmd, HDCamera camera, bool useMips, ref R
             fullresCoC = nextCoCTex;
         }
 
+        static void GetMipMapDimensions(RTHandle texture, int lod, out int width, out int height)
+        {
+            width = texture.rt.width;
+            height = texture.rt.height;
+
+            for (int level = 0; level < lod; ++level)
+            {
+                // Note: When the texture/mip size is an odd number, the size of the next level is rounded down.
+                // That's why we cannot find the actual size by doing (size >> lod).
+                width /= 2;
+                height /= 2;
+            }
+        }
+
         #endregion
 
         #region Depth Of Field (Physically based)
@@ -2375,8 +2399,12 @@ void DoPhysicallyBasedDepthOfField(CommandBuffer cmd, HDCamera camera, RTHandle
 
                 kernel = cs.FindKernel("KMain");
                 float sampleCount = Mathf.Max(m_DepthOfField.nearSampleCount, m_DepthOfField.farSampleCount);
-                float mipLevel = Mathf.Ceil(Mathf.Log(cocLimit, 2));
-                cmd.SetComputeVectorParam(cs, HDShaderIDs._Params, new Vector4(sampleCount, cocLimit, mipLevel, 0.0f));
+
+                // We only have up to 6 mip levels
+                float mipLevel = Mathf.Min(6, Mathf.Ceil(Mathf.Log(cocLimit, 2)));
+                GetMipMapDimensions(fullresCoC, (int)mipLevel, out var mipMapWidth, out var mipMapHeight);
+                cmd.SetComputeVectorParam(cs, HDShaderIDs._Params, new Vector4(sampleCount, cocLimit, 0.0f, 0.0f));
+                cmd.SetComputeVectorParam(cs, HDShaderIDs._Params2, new Vector4(mipLevel, mipMapWidth, mipMapHeight, 0.0f));
                 cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._InputTexture, source);
                 cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._InputCoCTexture, fullresCoC);
                 cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._OutputTexture, destination);

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/DoFGather.compute

@@ -11,11 +11,14 @@
 
 CBUFFER_START(cb0)
 float4 _Params;
+float4 _Params2;
 CBUFFER_END
 
 #define NumRings            _Params.x
 #define MaxCoCRadius        _Params.y
-#define MaxCoCMipLevel      _Params.z
+#define MaxCoCMipLevel      _Params2.x
+#define MaxCoCMipWidth      _Params2.y
+#define MaxCoCMipHeight     _Params2.z
 
 // Input textures
 TEXTURE2D_X(_InputTexture);
@@ -86,20 +89,9 @@ float GetCoCMaxRadius(int2 positionSS)
 #ifndef ADAPTIVE_RADIUS
     return MaxCoCRadius;
 #else
-    // We only have up to 6 mip levels 
-    int lod = min(6, MaxCoCMipLevel);
-
-    // TODO FIXME - (Seb) I added this patch for metal as it was causing a
-    // Shader error in 'DoFGather': 'GetDimensions' : no matching 5 parameter intrinsic method;
-    // But overall I am even not this if this call work on Metal.
-#if defined(SHADER_API_METAL)
-    uint3 size;
-    //  Texture2D<float4>.GetDimensions(uint, out uint width, out uint height, out uint levels) 
-    _InputCoCTexture.GetDimensions(lod, size.x, size.y, size.z);
-#else
-    uint4 size;
-    _InputCoCTexture.GetDimensions(lod, size.x, size.y, size.z, size.w);
-#endif
+
+    int lod = MaxCoCMipLevel;
+    uint2 size = float2(MaxCoCMipWidth, MaxCoCMipHeight);
 
     // Take RTHandleScale into account and odd texture dimension sizes (it's not enough to do a positionSS >> lod)
     uint2 coords = positionSS * _ScreenSize.zw * size.xy * _RTHandleScale.xy;