[HDRP] Fix issue with previous frame exposure texture being not null, but containing garbage

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

@@ -7,12 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [11.0.0] - 2020-10-21
 
 ### Changed
-
 - Removed the material pass probe volumes evaluation mode. 
 
 ### Fixed
 - Fixed probe volumes debug views.
-- Fixed picking for materials with depth offset.
 
 ## [10.2.0] - 2020-10-19
 
@@ -97,6 +95,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed an issue causing errors in GenerateMaxZ when opaque objects or decals are disabled. 
 - Fixed an issue with Bake button of Reflection Probe when in custom mode
 - Fixed exceptions related to the debug display settings when changing the default frame settings.
+- Fixed picking for materials with depth offset.
+- Fixed issue with exposure history being uninitialized on second frame.
 
 ### Changed
 - Combined occlusion meshes into one to reduce draw calls and state changes with XR single-pass.

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

@@ -148,12 +148,12 @@ private enum SMAAStage
 
         bool m_IsDoFHisotoryValid = false;
 
-        void FillEmptyExposureTexture()
+        static void SetExposureTextureToEmpty(RTHandle exposureTexture)
         {
             var tex = new Texture2D(1, 1, TextureFormat.RGHalf, false, true);
             tex.SetPixel(0, 0, new Color(1f, ColorUtils.ConvertExposureToEV100(1f), 0f, 0f));
             tex.Apply();
-            Graphics.Blit(tex, m_EmptyExposureTexture);
+            Graphics.Blit(tex, exposureTexture);
             CoreUtils.Destroy(tex);
         }
 
@@ -215,7 +215,7 @@ public PostProcessSystem(HDRenderPipelineAsset hdAsset, RenderPipelineResources
                 enableRandomWrite: true, name: "Debug Exposure Info"
             );
 
-            FillEmptyExposureTexture();
+            SetExposureTextureToEmpty(m_EmptyExposureTexture);
         }
 
         public void Cleanup()
@@ -323,7 +323,7 @@ public void CleanupNonRenderGraphResources()
         void CheckRenderTexturesValidity()
         {
             if (!m_EmptyExposureTexture.rt.IsCreated())
-                FillEmptyExposureTexture();
+                SetExposureTextureToEmpty(m_EmptyExposureTexture);
 
             if (!m_NonRenderGraphResourcesAvailable)
                 return;
@@ -1369,9 +1369,11 @@ static void GrabExposureHistoryTextures(HDCamera camera, out RTHandle previous,
             RTHandle Allocator(string id, int frameIndex, RTHandleSystem rtHandleSystem)
             {
                 // r: multiplier, g: EV100
-                return rtHandleSystem.Alloc(1, 1, colorFormat: k_ExposureFormat,
+                var rt = rtHandleSystem.Alloc(1, 1, colorFormat: k_ExposureFormat,
                     enableRandomWrite: true, name: $"{id} Exposure Texture {frameIndex}"
                 );
+                SetExposureTextureToEmpty(rt);
+                return rt;
             }
 
             // We rely on the RT history system that comes with HDCamera, but because it is swapped