Recompute FOV when generating PixelCoord To WorldSpace View Direction…

… Matrix #865

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

@@ -61,6 +61,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed light layers not correctly disabled when the lightlayers is set to Nothing and Lightlayers isn't enabled in HDRP Asset
 - Fixed AxF handling of roughness for Blinn-Phong type materials
 - Fixed AxF UI errors when surface type is switched to transparent
+- Fix issue that caused sky to incorrectly render when using a custom projection matrix.
 
 ### Changed
 - Shadowmask and realtime reflection probe property are hide in Quality settings

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

@@ -1221,6 +1221,10 @@ Matrix4x4 ComputePixelCoordToWorldSpaceViewDirectionMatrix(ViewConstants viewCon
             }
 
             float verticalFoV = camera.GetGateFittedFieldOfView() * Mathf.Deg2Rad;
+            if (!camera.usePhysicalProperties)
+            {
+                verticalFoV = Mathf.Atan(-1.0f / viewConstants.projMatrix[1, 1]) * 2;
+            }
             Vector2 lensShift = camera.GetGateFittedLensShift();
 
             return HDUtils.ComputePixelCoordToWorldSpaceViewDirectionMatrix(verticalFoV, lensShift, resolution, viewConstants.viewMatrix, false, aspect);