Fix NaN cause when a 0-length normal is generated and then normalized (#437)

* Avoid to normalize 0-length normals

* changelog

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

Author: FrancescoC-unity

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

@@ -573,6 +573,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed SceneView Draw Modes not being properly updated after opening new scene view panels or changing the editor layout.
 - 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
 - Improve MIP selection for decals on Transparents

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

@@ -99,7 +99,7 @@ public void GenerateNodeFunction(FunctionRegistry registry, GenerationMode gener
                         s.AppendLine("$precision dHdx = ddx(In);");
                         s.AppendLine("$precision dHdy = ddy(In);");
                         s.AppendLine("$precision3 surfGrad = surface * (dHdx*crossY + dHdy*crossX);");
-                        s.AppendLine("Out = normalize(TangentMatrix[2].xyz - (Strength * surfGrad));");
+                        s.AppendLine("Out = SafeNormalize(TangentMatrix[2].xyz - (Strength * surfGrad));");
 
                         if(outputSpace == OutputSpace.Tangent)
                             s.AppendLine("Out = TransformWorldToTangent(Out, TangentMatrix);");