attenuate color based on transmissive factor

Author: gkjohnson

src/shader/shaderMaterialSampling.js

@@ -233,7 +233,8 @@ vec3 transmissionDirection( vec3 wo, SurfaceRec surf ) {
 vec3 transmissionColor( vec3 wo, vec3 wi, SurfaceRec surf ) {
 
 	// only attenuate the color if it's on the way in
-	return surf.thinFilm || surf.frontFace ? surf.color : vec3( 1.0 );
+	vec3 col = surf.thinFilm || surf.frontFace ? surf.color : vec3( 1.0 );
+	return surf.transmission * col;
 
 }