Fixed ray-tracing variant of the checkerboard shader graph node #6301 (#6539)

Author: sebastienlagarde

com.unity.shadergraph/CHANGELOG.md

@@ -6,14 +6,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [12.1.3] - 2021-11-17
 
-Version Updated
-The version number for this package has increased due to a version update of a related graphics package.
+### Fixed
+
+ - Fixed the behavior of checkerboard node with raytracing
 
 ## [12.1.2] - 2021-10-22
 
 ### Fixed
-  - Fixed a ShaderGraph warning when connecting a node using Object Space BiTangent to the vertex stage [1361512] (https://issuetracker.unity3d.com/issues/shader-graph-cross-implicit-truncation-of-vector-type-errors-are-thrown-when-connecting-transform-node-to-vertex-block)
-
+ - Fixed a ShaderGraph warning when connecting a node using Object Space BiTangent to the vertex stage [1361512] (https://issuetracker.unity3d.com/issues/shader-graph-cross-implicit-truncation-of-vector-type-errors-are-thrown-when-connecting-transform-node-to-vertex-block)
+ 
 ## [12.1.1] - 2021-10-04
 
 ### Fixed

com.unity.shadergraph/Editor/Data/Nodes/Procedural/CheckerboardNode.cs

@@ -27,12 +27,12 @@ static string Unity_Checkerboard(
             return
 @"
 {
-    UV = (UV.xy + 0.5) * Frequency;
-    $precision2 distance3 = 4.0 * abs(frac(UV + 0.25) - 0.5) - 1.0;
 #if defined(SHADER_STAGE_RAY_TRACING)
-    int2 alpha = saturate(distance3 * FLT_MAX);
-    Out = lerp(ColorB, ColorA, alpha.x ^ alpha.y);
+    int2 checker = frac(Frequency * UV) > 0.5;
+    Out = checker.x ^ checker.y ? ColorA : ColorB;
 #else
+    UV = (UV.xy + 0.5) * Frequency;
+    $precision2 distance3 = 4.0 * abs(frac(UV + 0.25) - 0.5) - 1.0;
     $precision4 derivatives = $precision4(ddx(UV), ddy(UV));
     $precision2 duv_length = sqrt($precision2(dot(derivatives.xz, derivatives.xz), dot(derivatives.yw, derivatives.yw)));
     $precision2 scale = 0.35 / duv_length.xy;