[Backport 7.x.x] Fix NaN cause when a 0-length normal is generated and then normalized (#485)

* Backport changes

* changelog

Co-authored-by: sebastienlagarde <[email protected]>

Author: FrancescoC-unity

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

@@ -85,6 +85,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed transparent motion vectors not working when in MSAA.
 - VFX: Removed irrelevant queues in render queue selection from HDRP outputs
 - VFX: Motion Vector are correctly renderered with MSAA [Case 1240754](https://issuetracker.unity3d.com/product/unity/issues/guid/1240754/)
+- Fixed a cause of NaN when a normal of 0-length is generated (usually via shadergraph).
 
 ### Changed
 - Rejecting history for ray traced reflections based on a threshold evaluated on the neighborhood of the sampled history.

com.unity.render-pipelines.high-definition/Runtime/Material/MaterialUtilities.hlsl

@@ -32,8 +32,8 @@ void GetNormalWS(FragInputs input, float3 normalTS, out float3 normalWS, float3
     normalTS.xy *= flipSign;
 #endif // _DOUBLESIDED_ON
 
-    // We need to normalize as we use mikkt tangent space and this is expected (tangent space is not normalize)
-    normalWS = normalize(TransformTangentToWorld(normalTS, input.tangentToWorld));
+    // We need to normalize as we use mikkt tangent space and this is expected (tangent space is not normalized)
+    normalWS = SafeNormalize(TransformTangentToWorld(normalTS, input.tangentToWorld));
 
 #endif // SURFACE_GRADIENT
 }

com.unity.shadergraph/Editor/Data/Nodes/Artistic/Normal/NormalBlendNode.cs

@@ -58,7 +58,7 @@ static string Unity_NormalBlend(
 
             return @"
 {
-    Out = normalize($precision3(A.rg + B.rg, A.b * B.b));
+    Out = SafeNormalize($precision3(A.rg + B.rg, A.b * B.b));
 }
 ";
         }

com.unity.shadergraph/Editor/Data/Nodes/Artistic/Normal/NormalFromHeightNode.cs

@@ -91,7 +91,7 @@ public void GenerateNodeFunction(FunctionRegistry registry, GenerationMode gener
                         s.AppendLine("$precision3 inToNormal = ((((In + ddx(In)) - In) * crossY) + (((In + ddy(In)) - In) * crossX)) * sign(d);");
                         s.AppendLine("inToNormal.y *= -1.0;");
                         s.AppendNewLine();
-                        s.AppendLine("Out = normalize((d * TangentMatrix[2].xyz) - inToNormal);");
+                        s.AppendLine("Out = SafeNormalize((d * TangentMatrix[2].xyz) - inToNormal);");
 
                         if(outputSpace == OutputSpace.Tangent)
                             s.AppendLine("Out = TransformWorldToTangent(Out, TangentMatrix);");