Had forgotten to assign value when computed fresnel on several channels

mrf/materials/fresnel_functions.hpp

@@ -186,7 +186,7 @@ fresnel( RADIANCE_TYPE n1, RADIANCE_TYPE k1, RADIANCE_TYPE n2, RADIANCE_TYPE k2,
 
   for( unsigned int channel=0; channel < fresnel_value.size(); channel++)
   {
-    fresnel(std::complex<float>(n1[channel], k1[channel]), std::complex<float>(n2[channel], k2[channel]), cos_theta_d);
+    fresnel_value[channel] = fresnel(std::complex<float>(n1[channel], k1[channel]), std::complex<float>(n2[channel], k2[channel]), cos_theta_d);
   }
   return fresnel_value;
 }