Fix for NaN that can happen on area lights at a certain angle. (#4081)

FrancescoC-unity · sebastienlagarde · web-flow · commit 473ded180def · 2021-04-15T19:04:05.000+02:00
* Fix NaN with V1oV2 == -1

* Changelog

* Use clamping instead

Co-authored-by: sebastienlagarde &lt;sebastien@unity3d.com&gt;
diff --git a/com.unity.render-pipelines.core/ShaderLibrary/AreaLighting.hlsl b/com.unity.render-pipelines.core/ShaderLibrary/AreaLighting.hlsl
@@ -21,7 +21,8 @@ real3 ComputeEdgeFactor(real3 V1, real3 V2)
     if (V1oV2 < 0)
     {
         // Undo range reduction.
-        y = PI * rsqrt(saturate(1 - V1oV2 * V1oV2)) - y;
+        const float epsilon = 1e-5f;
+        y = PI * (max(epsilon, saturate(1 - V1oV2 * V1oV2))) - y;
     }
 
     return V1xV2 * y;
diff --git a/com.unity.render-pipelines.high-definition/CHANGELOG.md b/com.unity.render-pipelines.high-definition/CHANGELOG.md
@@ -146,6 +146,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed issue with the color space of AOVs (case 1324759)
 - Fixed issue with history buffers when using multiple AOVs (case 1323684).
 - Fixed camera preview with multi selection (case 1324126).
+- Fixed a NaN generating in Area light code.
 
 ### Changed
 - Changed Window/Render Pipeline/HD Render Pipeline Wizard to Window/Rendering/HDRP Wizard

Original file line number	Diff line number	Diff line change
`@@ -21,7 +21,8 @@ real3 ComputeEdgeFactor(real3 V1, real3 V2)`
`21`	`21`	`if (V1oV2 < 0)`
`22`	`22`	`{`
`23`	`23`	`// Undo range reduction.`
`24`		`- y = PI * rsqrt(saturate(1 - V1oV2 * V1oV2)) - y;`
	`24`	`+ const float epsilon = 1e-5f;`
	`25`	`+ y = PI * (max(epsilon, saturate(1 - V1oV2 * V1oV2))) - y;`
`25`	`26`	`}`
`26`	`27`
`27`	`28`	`return V1xV2 * y;`