Fix a Divide-by-Zero Warning for some Anisotropic Models (Fabric, Lit) (

#4636)

* Initialize the shading normal to a non-zero value for anisotropy

* Changelog

Co-authored-by: sebastienlagarde <sebastien@unity3d.com>

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

@@ -217,6 +217,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed a compilation issue for AxF carpaints on Vulkan (case 1314040).
 - Fixed the ray traced sub subsurface scattering debug mode not displaying only the RTSSS Data (case 1332904).
 - Fixed for discrepancies in intensity and saturation between screen space refraction and probe refraction.
+- Fixed a divide-by-zero warning for anisotropic shaders (Fabric, Lit).
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard

com.unity.render-pipelines.high-definition/Editor/Material/Fabric/ShaderGraph/ShaderPass.template.hlsl

@@ -44,6 +44,9 @@ void BuildSurfaceData(FragInputs fragInputs, inout SurfaceDescription surfaceDes
     #ifdef _MATERIAL_FEATURE_COTTON_WOOL
         surfaceData.materialFeatures |= MATERIALFEATUREFLAGS_FABRIC_COTTON_WOOL;
         $SurfaceDescription.Smoothness:                 surfaceData.perceptualSmoothness =      lerp(0.0, 0.6, surfaceDescription.Smoothness);
+    #else
+        // Initialize the normal to something non-zero to avoid div-zero warnings for anisotropy.
+        surfaceData.normalWS = float3(0, 1, 0);
     #endif
 
     #ifdef _MATERIAL_FEATURE_SUBSURFACE_SCATTERING

com.unity.render-pipelines.high-definition/Editor/Material/Lit/ShaderGraph/ShaderPass.template.hlsl

@@ -57,6 +57,9 @@ void BuildSurfaceData(FragInputs fragInputs, inout SurfaceDescription surfaceDes
 
     #ifdef _MATERIAL_FEATURE_ANISOTROPY
         surfaceData.materialFeatures |= MATERIALFEATUREFLAGS_LIT_ANISOTROPY;
+
+        // Initialize the normal to something non-zero to avoid a div-zero warning for anisotropy.
+        surfaceData.normalWS = float3(0, 1, 0);
     #endif
 
     #ifdef _MATERIAL_FEATURE_IRIDESCENCE