Fix path traced DoF focusing issue (#732)

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

@@ -637,6 +637,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed a vulkan and metal warning in the SSGI compute shader.
 - Fixed an exception due to the color pyramid not allocated when SSGI is enabled.
 - Fixed an issue with the first Depth history was incorrectly copied.
+- Fixed path traced DoF focusing issue
 
 ### Changed
 - Improve MIP selection for decals on Transparents

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

@@ -277,7 +277,6 @@ void RenderPathTracing(HDCamera hdCamera, CommandBuffer cmd, RTHandle outputText
                 cmd.SetRayTracingTextureParam(pathTracingShader, HDShaderIDs._RadianceTexture, m_RadianceTexture);
                 cmd.SetRayTracingMatrixParam(pathTracingShader, HDShaderIDs._PixelCoordToViewDirWS, hdCamera.mainViewConstants.pixelCoordToViewDirWS);
                 cmd.SetRayTracingVectorParam(pathTracingShader, HDShaderIDs._PathTracedDoFConstants, ComputeDoFConstants(hdCamera, m_PathTracingSettings));
-                cmd.SetRayTracingVectorParam(pathTracingShader, HDShaderIDs._InvViewportScaleBias, HDUtils.ComputeInverseViewportScaleBias(hdCamera));
 
                 // Run the computation
                 cmd.DispatchRays(pathTracingShader, "RayGen", (uint)hdCamera.actualWidth, (uint)hdCamera.actualHeight, 1);

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

@@ -25,7 +25,6 @@ float3   _RaytracingCameraClearColor;
 
 // DoF related parameters
 float4   _PathTracedDoFConstants;     // x: aperture radius, y: focus distance, zw: unused
-float4   _InvViewportScaleBias;
 
 // Output(s)
 RWTexture2D<float4> _RadianceTexture;
@@ -71,39 +70,30 @@ void RayGen()
     jitteredPixelCoord.x += GetSample(currentPixelCoord, _RaytracingSampleIndex, 40);
     jitteredPixelCoord.y += GetSample(currentPixelCoord, _RaytracingSampleIndex, 41);
 
-    float3 directionWS;
-    float3 cameraPosWS;
+    // Compute the ray direction from those coordinates (for zero aperture)
+    float3 directionWS = -normalize(mul(jitteredPixelCoord, (float3x3)_PixelCoordToViewDirWS));
+    float3 cameraPosWS = _WorldSpaceCameraPos;
 
     float apertureRadius = _PathTracedDoFConstants.x;
-    if (apertureRadius == 0.0)
-    {
-        // Compute the ray direction from those coordinates (fast path for zero aperture)
-        directionWS = -normalize(mul(jitteredPixelCoord, (float3x3)_PixelCoordToViewDirWS));
-        cameraPosWS = _WorldSpaceCameraPos;
-    }
-    else
+    if (apertureRadius > 0.0)
     {
         // Compute the ray origin and direction for a lens with non-zero aperture
 
-        // Apply the inverse viewport transform to go from viewport coordinates to NDC
-        jitteredPixelCoord.xy = jitteredPixelCoord.xy * _InvViewportScaleBias.xy + _InvViewportScaleBias.zw;
-
         // Sample the lens apperture using the next available dimensions (we use 40 for path tracing, 2 for sub-pixel jittering, 64 for SSS -> 106, 107)
         float r1 = GetSample(currentPixelCoord, _RaytracingSampleIndex, 106);
         float r2 = GetSample(currentPixelCoord, _RaytracingSampleIndex, 107);
         float2 uv = apertureRadius * SampleDiskUniform(r1, r2);
 
         // Compute the new ray origin ( _ViewMatrix[0] = right, _ViewMatrix[1] = up, _ViewMatrix[2] = forward )
-        float focusDistance = _PathTracedDoFConstants.y;
-        float3 focusPoint = _WorldSpaceCameraPos - _ViewMatrix[2] * focusDistance;
-        cameraPosWS = _WorldSpaceCameraPos + _ViewMatrix[0] * uv.x + _ViewMatrix[1] * uv.y;
+        cameraPosWS += _ViewMatrix[0] * uv.x + _ViewMatrix[1] * uv.y;
 
-        // Create the new view matrix 
-        float3 newForward = normalize(focusPoint - cameraPosWS);
-        float3 newRight = cross(newForward, _ViewMatrix[1]);
-        float3x3 newViewMatrix = GetLocalFrame(newForward, newRight);
+        // Compute the focus point by intersecting the pinhole ray with the focus plane
+        float focusDistance = _PathTracedDoFConstants.y;
+        float t = focusDistance / dot(directionWS, _ViewMatrix[2]);
+        float3 focusPointWS = _WorldSpaceCameraPos - t * directionWS;
 
-        directionWS = normalize(mul(jitteredPixelCoord, newViewMatrix));
+        // The new ray direction should pass through the focus point
+        directionWS = normalize(focusPointWS - cameraPosWS);
     }
 
     // Create the ray descriptor for this pixel

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

@@ -196,23 +196,6 @@ internal static Matrix4x4 ComputePixelCoordToWorldSpaceViewDirectionMatrix(float
             return Matrix4x4.Transpose(worldToViewMatrix.transpose * viewSpaceRasterTransform);
         }
 
-        // Scale and bias to transform unnormalized viewport/pixel coordinates to normalized device coordinates
-        internal static Vector4 ComputeInverseViewportScaleBias(HDCamera hdCamera)
-        {
-            float verticalFoV = hdCamera.camera.GetGateFittedFieldOfView() * Mathf.Deg2Rad;
-            Vector2 lensShift = hdCamera.camera.GetGateFittedLensShift();
-
-            float aspectRatio = hdCamera.camera.aspect < 0 ? hdCamera.screenSize.x * hdCamera.screenSize.w : hdCamera.camera.aspect;
-            float tanHalfVertFoV = Mathf.Tan(0.5f * verticalFoV);
-
-            // See the comment in ComputePixelCoordToWorldSpaceViewDirectionMatrix for the derivation
-            return new Vector4(
-                -2.0f * hdCamera.screenSize.z * tanHalfVertFoV * aspectRatio,
-                -2.0f * hdCamera.screenSize.w * tanHalfVertFoV,
-                (1.0f - 2.0f * lensShift.x) * tanHalfVertFoV * aspectRatio,
-                (1.0f - 2.0f * lensShift.y) * tanHalfVertFoV);
-        }
-
         internal static float ComputZPlaneTexelSpacing(float planeDepth, float verticalFoV, float resolutionY)
         {
             float tanHalfVertFoV = Mathf.Tan(0.5f * verticalFoV);