Minor adjustments to TAA anti flicker

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

@@ -647,6 +647,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Added override Ambient Occlusion option on debug windows
 - Added Custom Post Processes with 3 injection points: Before Transparent, Before Post Process and After Post Process
 - Added draft of minimal interactive path tracing (experimental) based on DXR API - Support only 4 area light, lit and unlit shader (non-shadergraph)
+- Small adjustments to TAA anti flicker (more aggressive on high values).
 
 ### Fixed
 - Fixed wizard infinite loop on cancellation

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

@@ -955,7 +955,10 @@ void DoTemporalAntialiasing(CommandBuffer cmd, HDCamera camera, RTHandle source,
             float maxAntiflicker = 3.5f;
             float motionRejectionMultiplier = Mathf.Lerp(0.0f, 250.0f, camera.taaMotionVectorRejection * camera.taaMotionVectorRejection * camera.taaMotionVectorRejection);
 
-            var taaParameters = new Vector4(camera.taaHistorySharpening, Mathf.Lerp(minAntiflicker, maxAntiflicker, camera.taaAntiFlicker), motionRejectionMultiplier, 0.0f);
+            // The anti flicker becomes much more aggressive on higher values
+            float temporalContrastForMaxAntiFlicker = 0.7f - Mathf.Lerp(0.0f, 0.3f, Mathf.SmoothStep(0.5f, 1.0f, camera.taaAntiFlicker));
+
+            var taaParameters = new Vector4(camera.taaHistorySharpening, Mathf.Lerp(minAntiflicker, maxAntiflicker, camera.taaAntiFlicker), motionRejectionMultiplier, temporalContrastForMaxAntiFlicker);
             Vector2 historySize = new Vector2(prevHistory.referenceSize.x * prevHistory.scaleFactor.x,
                                               prevHistory.referenceSize.y * prevHistory.scaleFactor.y);
             var rtScaleForHistory = camera.historyRTHandleProperties.rtHandleScale;

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/TemporalAntiAliasing.shader

@@ -81,6 +81,7 @@ Shader "Hidden/HDRP/TemporalAA"
         #define _HistorySharpening _TaaPostParameters.x
         #define _AntiFlickerIntensity _TaaPostParameters.y
         #define _SpeedRejectionIntensity _TaaPostParameters.z
+        #define _ContrastForMaxAntiFlicker _TaaPostParameters.w
 
 
         TEXTURE2D_X(_InputVelocityMagnitudeHistory);
@@ -162,7 +163,7 @@ Shader "Hidden/HDRP/TemporalAA"
             // --------------- Get neighbourhood information and clamp history --------------- 
             float colorLuma = GetLuma(filteredColor);
             float historyLuma = GetLuma(history);
-            GetNeighbourhoodCorners(samples, historyLuma, colorLuma, _AntiFlickerIntensity);
+            GetNeighbourhoodCorners(samples, historyLuma, colorLuma, float2(_AntiFlickerIntensity, _ContrastForMaxAntiFlicker));
 
             history = GetClippedHistory(filteredColor, history, samples.minNeighbour, samples.maxNeighbour);
             filteredColor = SharpenColor(samples, filteredColor, sharpenStrength);

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/TemporalAntialiasing.hlsl

@@ -526,7 +526,7 @@ void MinMaxNeighbourhood(inout NeighbourhoodSamples samples)
     samples.avgNeighbour *= rcp(NEIGHBOUR_COUNT);
 }
 
-void VarianceNeighbourhood(inout NeighbourhoodSamples samples, float historyLuma, float colorLuma, float antiFlicker)
+void VarianceNeighbourhood(inout NeighbourhoodSamples samples, float historyLuma, float colorLuma, float2 antiFlickerParams)
 {
     CTYPE moment1 = 0;
     CTYPE moment2 = 0;
@@ -554,19 +554,18 @@ void VarianceNeighbourhood(inout NeighbourhoodSamples samples, float historyLuma
 #if ANTI_FLICKER
     stDevMultiplier = 1.4;
     float temporalContrast = saturate(abs(colorLuma - historyLuma) / Max3(0.2, colorLuma, historyLuma));
-    stDevMultiplier += lerp(0.0, antiFlicker, smoothstep(0.1, 0.7, temporalContrast));
+    stDevMultiplier += lerp(0.0, antiFlickerParams.x, smoothstep(0.05, antiFlickerParams.y, temporalContrast));
 #endif
-
-    samples.minNeighbour = moment1 - stDevMultiplier * stdDev;
-    samples.maxNeighbour = moment1 + stDevMultiplier * stdDev;
+    samples.minNeighbour = moment1 - stdDev * stDevMultiplier;
+    samples.maxNeighbour = moment1 + stdDev * stDevMultiplier;
 }
 
-void GetNeighbourhoodCorners(inout NeighbourhoodSamples samples, float historyLuma, float colorLuma, float antiFlicker)
+void GetNeighbourhoodCorners(inout NeighbourhoodSamples samples, float historyLuma, float colorLuma, float2 antiFlickerParams)
 {
 #if NEIGHBOUROOD_CORNER_METHOD == MINMAX
     MinMaxNeighbourhood(samples);
 #else
-    VarianceNeighbourhood(samples, historyLuma, colorLuma, antiFlicker);
+    VarianceNeighbourhood(samples, historyLuma, colorLuma, antiFlickerParams);
 #endif
 }