Merge remote-tracking branch 'refs/remotes/origin/master' into Update-material-framework

Assets/ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/VaryingMesh.hlsl

     // For now do some test by keeping code consistent with previous visual.
 #ifdef SURFACE_GRADIENT
     // Normalize normalWS vector but keep the renormFactor to apply it to bitangent and tangent
-    float renormFactor = 1.0 / length(input.interpolators1);
-    float3 normalWS = renormFactor * input.interpolators1;
+	float3 unnormalizedNormalWS = input.interpolators1.xyz;
+    float renormFactor = 1.0 / length(unnormalizedNormalWS);
-    float3x3 worldToTangent = CreateWorldToTangent(normalWS, tangentWS.xyz, tangentWS.w);
-    output.worldToTangent[0] = worldToTangent[0];
-    // prepare for surfgrad formulation without breaking compliance (use exact same scale as applied to interpolated vertex normal to avoid breaking compliance).
+    float3x3 worldToTangent = CreateWorldToTangent(unnormalizedNormalWS, tangentWS.xyz, tangentWS.w);		// this is the mikktspace transformation (must use unnormalized attributes)
+
+	// surface gradient based formulation requires a unit length initial normal. We can maintain compliance with mikkts
+	// by uniformly scaling all 3 vectors since normalization of the perturbed normal will cancel it.
+    output.worldToTangent[0] = worldToTangent[0] * renormFactor;
+
+	float3 normalWS = output.worldToTangent[2];
 #else
     // TODO: Check if we must do like for surface gradient (i.e not normalize ?) For now, for consistency with previous code we normalize
     // Normalize after the interpolation