Fix normal map filtering for both base roughnesses and coat normal map.

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/StackLit/StackLit.cs

             [SurfaceDataAttributes(new string[]{"Coat Normal", "Coat Normal View Space"}, true)]
             public Vector3 coatNormalWS;
 
-            [SurfaceDataAttributes("Average Normal Length A")]
-            public float averageNormalLengthA;
+            [SurfaceDataAttributes("Average Normal Length")]
+            public float averageNormalLength;
-            [SurfaceDataAttributes("Average Normal Length B")]
-            public float averageNormalLengthB;
+            [SurfaceDataAttributes("Average Coat Normal Length")]
+            public float averageCoatNormalLength;
 
             [SurfaceDataAttributes("Smoothness A")]
             public float perceptualSmoothnessA;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/StackLit/StackLit.cs.hlsl

 #define DEBUGVIEW_STACKLIT_SURFACEDATA_GEOMETRIC_NORMAL_VIEW_SPACE (1308)
 #define DEBUGVIEW_STACKLIT_SURFACEDATA_COAT_NORMAL (1309)
 #define DEBUGVIEW_STACKLIT_SURFACEDATA_COAT_NORMAL_VIEW_SPACE (1310)
-#define DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH_A (1311)
-#define DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH_B (1312)
+#define DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH (1311)
+#define DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_COAT_NORMAL_LENGTH (1312)
 #define DEBUGVIEW_STACKLIT_SURFACEDATA_SMOOTHNESS_A (1313)
 #define DEBUGVIEW_STACKLIT_SURFACEDATA_SMOOTHNESS_B (1314)
 #define DEBUGVIEW_STACKLIT_SURFACEDATA_LOBE_MIXING (1315)
     float3 normalWS;
     float3 geomNormalWS;
     float3 coatNormalWS;
-    float averageNormalLengthA;
-    float averageNormalLengthB;
+    float averageNormalLength;
+    float averageCoatNormalLength;
     float perceptualSmoothnessA;
     float perceptualSmoothnessB;
     float lobeMix;
         case DEBUGVIEW_STACKLIT_SURFACEDATA_COAT_NORMAL_VIEW_SPACE:
             result = surfacedata.coatNormalWS * 0.5 + 0.5;
             break;
-        case DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH_A:
-            result = surfacedata.averageNormalLengthA.xxx;
+        case DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH:
+            result = surfacedata.averageNormalLength.xxx;
-        case DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_NORMAL_LENGTH_B:
-            result = surfacedata.averageNormalLengthB.xxx;
+        case DEBUGVIEW_STACKLIT_SURFACEDATA_AVERAGE_COAT_NORMAL_LENGTH:
+            result = surfacedata.averageCoatNormalLength.xxx;
             break;
         case DEBUGVIEW_STACKLIT_SURFACEDATA_SMOOTHNESS_A:
             result = surfacedata.perceptualSmoothnessA.xxx;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/StackLit/StackLit.hlsl

     bsdfData.perceptualRoughnessB = PerceptualSmoothnessToPerceptualRoughness(surfaceData.perceptualSmoothnessB);
 
     // Specular AA / Filtering.
-    bsdfData.perceptualRoughnessA = FilterRoughness(bsdfData.perceptualRoughnessA, bsdfData.geomNormalWS, surfaceData.averageNormalLengthA);
-    bsdfData.perceptualRoughnessB = FilterRoughness(bsdfData.perceptualRoughnessB, bsdfData.geomNormalWS, surfaceData.averageNormalLengthB);
+    bsdfData.perceptualRoughnessA = FilterRoughness(bsdfData.perceptualRoughnessA, bsdfData.geomNormalWS, surfaceData.averageNormalLength);
+    bsdfData.perceptualRoughnessB = FilterRoughness(bsdfData.perceptualRoughnessB, bsdfData.geomNormalWS, surfaceData.averageNormalLength);
     
     bsdfData.lobeMix = surfaceData.lobeMix;
 
 
     if (HasFeatureFlag(surfaceData.materialFeatures, MATERIALFEATUREFLAGS_STACK_LIT_COAT))
     {
+        FillMaterialCoatData(PerceptualSmoothnessToPerceptualRoughness(surfaceData.coatPerceptualSmoothness),
+                             surfaceData.coatIor, surfaceData.coatThickness, surfaceData.coatExtinction, bsdfData);
+
+            // Specular AA / Filtering.
+            bsdfData.coatPerceptualRoughness = FilterRoughness(bsdfData.coatPerceptualRoughness, bsdfData.geomNormalWS, surfaceData.averageCoatNormalLength);
-        FillMaterialCoatData(PerceptualSmoothnessToPerceptualRoughness(surfaceData.coatPerceptualSmoothness),
-                             surfaceData.coatIor, surfaceData.coatThickness, surfaceData.coatExtinction, bsdfData);
 
         // vlayering:
         // We can't calculate final roughnesses including anisotropy right away in this case: we will either do it

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/StackLit/StackLitData.hlsl

     surfaceData.normalWS = SurfaceGradientResolveNormal(input.worldToTangent[2], gradient.xyz);
     surfaceData.coatNormalWS = SurfaceGradientResolveNormal(input.worldToTangent[2], coatGradient.xyz);
 
-    surfaceData.averageNormalLengthA = gradient.w;
-    surfaceData.averageNormalLengthB = coatGradient.w;
+    surfaceData.averageNormalLength = gradient.w;
+    surfaceData.averageCoatNormalLength = coatGradient.w;
 
     // TODO: decal etc.