float CookTorrenceGeometricShadowingFunction (float NdotL, float NdotV, 
float VdotH, float NdotH){
	float Gs = min(1.0, min(2*NdotH*NdotV / VdotH, 
2*NdotH*NdotL / VdotH));
	return  (Gs);
}