Avoid NaN issues in rare cases in the Cook-Torrance shader

The dot product may sometimes be very slightly over 1.0, making the
first argument to pow negative and giving undefined results.

diff --git a/shaderlib/cooktorrance.glsl b/shaderlib/cooktorrance.glsl
index d834cee462d429ca2d439107caca5ad3e1c55c8d..02d697b087c640572a2ed0ebad15fe655ff4f1d2 100644 (file)
--- a/shaderlib/cooktorrance.glsl
+++ b/shaderlib/cooktorrance.glsl
@@ -114,7 +114,7 @@ vec3 fresnel_schlick(vec3 halfway, vec3 look, vec3 base_color, float metalness)
 {
        // 0.04 is a decent approximation for dielectric base reflectivity
        vec3 f0 = mix(vec3(0.04), base_color, metalness);
-       return mix(f0, vec3(1.0), pow(1.0-dot(halfway, look), 5.0));
+       return mix(f0, vec3(1.0), pow(max(1.0-dot(halfway, look), 0.0), 5.0));
 }
 
 /* Computes the full contribution of a single light */