[2023.3][URP] Fixing an issue with incorrect matrix data when Scene and Game windows are open. (UUM-63267)

Fixes UUM-63267.
In non-RenderGraph, the main and additional light shadow passes didn't have the correct data in the WorldToCamera matrix. This is due to it being set after they've been run. This PR fixes that.

Author: ellioman

Packages/com.unity.render-pipelines.universal/Runtime/Passes/AdditionalLightsShadowCasterPass.cs

@@ -711,6 +711,11 @@ void RenderAdditionalShadowmapAtlas(RasterCommandBuffer cmd, ref PassData data,
 
             using (new ProfilingScope(cmd, ProfilingSampler.Get(URPProfileId.AdditionalLightsShadow)))
             {
+                // For non-RG, need set the worldToCamera Matrix as that is not set for passes executed before normal rendering,
+                // otherwise shadows will behave incorrectly when Scene and Game windows are open at the same time (UUM-63267).
+                if (!useRenderGraph)
+                    ShadowUtils.SetWorldToCameraMatrix(cmd, data.viewMatrix);
+
                 bool anyShadowSliceRenderer = false;
                 int shadowSlicesCount = m_ShadowSliceToAdditionalLightIndex.Count;
                 if (shadowSlicesCount > 0)
@@ -826,6 +831,7 @@ private class PassData
         {
             internal UniversalLightData lightData;
             internal UniversalShadowData shadowData;
+            internal Matrix4x4 viewMatrix;
             internal bool stripShadowsOffVariants;
 
             internal AdditionalLightsShadowCasterPass pass;
@@ -846,6 +852,7 @@ private void InitPassData(ref PassData passData, UniversalCameraData cameraData,
 
             passData.lightData = lightData;
             passData.shadowData = shadowData;
+            passData.viewMatrix = cameraData.GetViewMatrix();
             passData.stripShadowsOffVariants = cameraData.renderer.stripShadowsOffVariants;
 
             passData.emptyShadowmap = m_CreateEmptyShadowmap;

Packages/com.unity.render-pipelines.universal/Runtime/Passes/MainLightShadowCasterPass.cs

@@ -268,8 +268,13 @@ void RenderMainLightCascadeShadowmap(RasterCommandBuffer cmd, ref PassData data,
 
             using (new ProfilingScope(cmd, ProfilingSampler.Get(URPProfileId.MainLightShadow)))
             {
-                // Need to start by setting the Camera position as that is not set for passes executed before normal rendering
-                cmd.SetGlobalVector(ShaderPropertyId.worldSpaceCameraPos, data.cameraData.worldSpaceCameraPos);
+                // Need to start by setting the Camera position and worldToCamera Matrix as that is not set for passes executed before normal rendering
+                ShadowUtils.SetCameraPosition(cmd, data.cameraData.worldSpaceCameraPos);
+
+                // For non-RG, need set the worldToCamera Matrix as that is not set for passes executed before normal rendering,
+                // otherwise shadows will behave incorrectly when Scene and Game windows are open at the same time (UUM-63267).
+                if (!isRenderGraph)
+                    ShadowUtils.SetWorldToCameraMatrix(cmd, data.cameraData.GetViewMatrix());
 
                 for (int cascadeIndex = 0; cascadeIndex < m_ShadowCasterCascadesCount; ++cascadeIndex)
                 {

Packages/com.unity.render-pipelines.universal/Runtime/ShadowUtils.cs

@@ -489,10 +489,6 @@ public static void SetupShadowCasterConstantBuffer(CommandBuffer cmd, ref Visibl
             SetupShadowCasterConstantBuffer(CommandBufferHelpers.GetRasterCommandBuffer(cmd), ref shadowLight, shadowBias);
         }
 
-        private static int _ShadowBias = Shader.PropertyToID("_ShadowBias");
-        private static int _LightDirection = Shader.PropertyToID("_LightDirection");
-        private static int _LightPosition = Shader.PropertyToID("_LightPosition");
-
         internal static void SetupShadowCasterConstantBuffer(RasterCommandBuffer cmd, ref VisibleLight shadowLight, Vector4 shadowBias)
         {
             SetShadowBias(cmd, shadowBias);
@@ -508,17 +504,31 @@ internal static void SetupShadowCasterConstantBuffer(RasterCommandBuffer cmd, re
 
         internal static void SetShadowBias(RasterCommandBuffer cmd, Vector4 shadowBias)
         {
-            cmd.SetGlobalVector(_ShadowBias, shadowBias);
+            cmd.SetGlobalVector(ShaderPropertyId.shadowBias, shadowBias);
         }
 
         internal static void SetLightDirection(RasterCommandBuffer cmd, Vector3 lightDirection)
         {
-            cmd.SetGlobalVector(_LightDirection, new Vector4(lightDirection.x, lightDirection.y, lightDirection.z, 0.0f));
+            cmd.SetGlobalVector(ShaderPropertyId.lightDirection, new Vector4(lightDirection.x, lightDirection.y, lightDirection.z, 0.0f));
         }
 
         internal static void SetLightPosition(RasterCommandBuffer cmd, Vector3 lightPosition)
         {
-            cmd.SetGlobalVector(_LightPosition, new Vector4(lightPosition.x, lightPosition.y, lightPosition.z, 1.0f));
+            cmd.SetGlobalVector(ShaderPropertyId.lightPosition, new Vector4(lightPosition.x, lightPosition.y, lightPosition.z, 1.0f));
+        }
+
+        internal static void SetCameraPosition(RasterCommandBuffer cmd, Vector3 worldSpaceCameraPos)
+        {
+            cmd.SetGlobalVector(ShaderPropertyId.worldSpaceCameraPos, worldSpaceCameraPos);
+        }
+
+        internal static void SetWorldToCameraMatrix(RasterCommandBuffer cmd, Matrix4x4 viewMatrix)
+        {
+            // There's an inconsistency in handedness between unity_matrixV and unity_WorldToCamera
+            // Unity changes the handedness of unity_WorldToCamera (see Camera::CalculateMatrixShaderProps)
+            // we will also change it here to avoid breaking existing shaders. (case 1257518)
+            Matrix4x4 worldToCameraMatrix = Matrix4x4.Scale(new Vector3(1.0f, 1.0f, -1.0f)) * viewMatrix;
+            cmd.SetGlobalMatrix(ShaderPropertyId.worldToCameraMatrix, worldToCameraMatrix);
         }
 
         private static RenderTextureDescriptor GetTemporaryShadowTextureDescriptor(int width, int height, int bits)

Packages/com.unity.render-pipelines.universal/Runtime/UniversalRenderPipelineCore.cs

@@ -849,6 +849,10 @@ internal static class ShaderPropertyId
         public static readonly int worldToCameraMatrix = Shader.PropertyToID("unity_WorldToCamera");
         public static readonly int cameraToWorldMatrix = Shader.PropertyToID("unity_CameraToWorld");
 
+        public static readonly int shadowBias = Shader.PropertyToID("_ShadowBias");
+        public static readonly int lightDirection = Shader.PropertyToID("_LightDirection");
+        public static readonly int lightPosition = Shader.PropertyToID("_LightPosition");
+
         public static readonly int cameraWorldClipPlanes = Shader.PropertyToID("unity_CameraWorldClipPlanes");
 
         public static readonly int billboardNormal = Shader.PropertyToID("unity_BillboardNormal");