[Fix] Fix to area lights (disk, sphere) occasionally generating -Inf …

…pixels (#7015)

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

src/scene/shader-lib/chunks/lit/frag/ltc.js

@@ -322,7 +322,7 @@ float LTC_EvaluateDisk(vec3 N, vec3 V, vec3 P, mat3 Minv, Coords points)
         V2 *= sqrt(b);
     }
 
-    vec3 V3 = cross(V1, V2);
+    vec3 V3 = normalize(cross(V1, V2));
     if (dot(C, V3) < 0.0)
         V3 *= -1.0;
 
@@ -356,7 +356,7 @@ float LTC_EvaluateDisk(vec3 N, vec3 V, vec3 P, mat3 Minv, Coords points)
     float L1 = sqrt(-e2 / e3);
     float L2 = sqrt(-e2 / e1);
 
-    float formFactor = L1 * L2 * inversesqrt((1.0 + L1 * L1) * (1.0 + L2 * L2));
+    float formFactor = max(0.0, L1 * L2 * inversesqrt((1.0 + L1 * L1) * (1.0 + L2 * L2)));
     
     const float LUT_SIZE = 64.0;
     const float LUT_SCALE = ( LUT_SIZE - 1.0 ) / LUT_SIZE;