Disable TAA sharpening on alpha

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

@@ -150,6 +150,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fix potential NaN on apply distortion pass.
 - Fixed the camera controller in the template with the old input system (case 1326816).
 - Fixed broken Lanczos filter artifacts on ps4, caused by a very aggressive epsilon (case 1328904)
+- Disable TAA sharpening on alpha channel.
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard

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

@@ -11,7 +11,6 @@
     #define CTYPE_SWIZZLE xyz
 #endif
 
-
 #if UNITY_REVERSED_Z
     #define COMPARE_DEPTH(a, b) step(b, a)
 #else
@@ -49,6 +48,8 @@ float4 Fetch4Array(Texture2DArray tex, uint slot, float2 coords, float2 offset,
 // Options
 // ---------------------------------------------------
 
+#define SHARPEN_ALPHA 0 // switch to 1 if you want to enable TAA sharpenning on alpha channel
+
 // History sampling options
 #define BILINEAR 0
 #define BICUBIC_5TAP 1
@@ -717,5 +718,11 @@ CTYPE SharpenColor(NeighbourhoodSamples samples, CTYPE color, float sharpenStren
     linearC = linearC + (linearC - linearAvg) * sharpenStrength * 3;
     linearC = clamp(linearC, 0, CLAMP_MAX);
 #endif
-    return linearC * PerceptualWeight(linearC);
+    CTYPE outputSharpened = linearC * PerceptualWeight(linearC);
+
+#if (SHARPEN_ALPHA == 0 && defined(ENABLE_ALPHA))
+    outputSharpened.a = color.a;
+#endif
+
+    return outputSharpened;
 }