[HDRP][Compositor] Update the compositor output when not in play mode

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 issue with composition graphs that include virtual textures, cubemaps and other non-2D textures (cases 1263347, 1265638).
 - Fixed issues when selecting a new composition graph or setting it to None (cases 1263350, 1266202)
 - Fixed ArgumentNullException when saving shader graphs after removing the compositor from the scene (case 1268658)
+- Fixed issue with updating the compositor output when not in play mode (case 1266216)
 
 ### Changed
 - Preparation pass for RTSSShadows to be supported by render graph.

com.unity.render-pipelines.high-definition/Editor/Compositor/CompositorWindow.cs

@@ -48,8 +48,30 @@ void Update()
             m_TimeSinceLastRepaint += Time.deltaTime;
 
             // This ensures that layer thumbnails are updated at least 4 times per second (redrawing the UI on every frame is too CPU intensive)
-            if (m_TimeSinceLastRepaint > 0.25f)
+            const float timeThreshold = 0.25f;
+            if (m_TimeSinceLastRepaint > timeThreshold)
+            {
                 Repaint();
+
+                // [case 1266216] Ensure the game view gets repainted a few times per second even when we are not in play mode.
+                // This ensures that we will not always display the first frame, which might have some artifacts for effects that require temporal data 
+                if (!Application.isPlaying)
+                {
+                    CompositionManager compositor = CompositionManager.GetInstance();
+                    if (compositor && compositor.enableOutput)
+                    {
+                        compositor.timeSinceLastRepaint += Time.deltaTime;
+                        // The Editor will repaint the game view if the scene view is also visible (side-by-side) and
+                        // "always refresh" is enabled so we call manually repaint only if enough time has passed
+                        if (compositor.timeSinceLastRepaint > timeThreshold)
+                        {
+                            compositor.Repaint();
+                        }
+                    }
+
+                }
+            }
+
         }
 
         void OnGUI()

com.unity.render-pipelines.high-definition/Runtime/Compositor/CompositionManager.cs

@@ -45,6 +45,8 @@ public enum AlphaChannelSupport
 
         internal AlphaChannelSupport m_AlphaSupport = AlphaChannelSupport.RenderingAndPostProcessing;
 
+        internal float timeSinceLastRepaint;
+
         public bool enableOutput
         {
             get
@@ -722,6 +724,15 @@ public RenderTexture GetRenderTarget(int indx)
             return null;
         }
 
+        public void Repaint()
+        {
+            for (int indx = 0; indx < m_InputLayers.Count; indx++)
+            {
+                if (m_InputLayers[indx].camera)
+                    m_InputLayers[indx].camera.Render();
+            }
+        }
+
         void CustomRender(ScriptableRenderContext context, HDCamera camera)
         {
             if (camera == null || camera.camera == null || m_Material == null || m_Shader == null)
@@ -733,6 +744,8 @@ void CustomRender(ScriptableRenderContext context, HDCamera camera)
             }
 
 
+            timeSinceLastRepaint = 0;
+
             // set shader uniforms
             m_CompositionProfile.CopyPropertiesToMaterial(m_Material);