public override int GetHashCode()
 {
     unchecked
     {
         int hashCode = (Fresnel != null ? Fresnel.GetHashCode() : 0);
         hashCode = (hashCode * 397) ^ (Visibility != null ? Visibility.GetHashCode() : 0);
         hashCode = (hashCode * 397) ^ (NormalDistribution != null ? NormalDistribution.GetHashCode() : 0);
         return(hashCode);
     }
 }