public Vector3 ComputeDirectLightContribution()
{
Vector3 specularColor = MaterialPixelStream.MaterialSpecularVisible;
Vector3 fresnel = Fresnel.Compute(specularColor);
float visibility = Visibility.Compute();
float normalDistribution = NormalDistribution.Compute();
Vector3 reflected = fresnel * visibility * normalDistribution / 4.0f;
return(reflected * LightStream.LightSpecularColorNDotL);
}