void PhongModel(DVector3 normal, DVector3 pos, ref int cr, ref int cg, ref int cb)
{
// ambient
double AmbientComponent = Ka * Ia;
double CameraZPosition = 220.0;
// diffuse
double distance = (new DVector3(0.0, 0.0, CameraZPosition) - pos).GetLength();
DVector3 L = LightPosition - pos;
L /= L.GetLength();
normal /= normal.GetLength();
double LNcos = DVector3.DotProduct(L, normal);
double DiffuseComponent = (Kd * Il) / (K + distance) * Clamp(LNcos, 0.0, 1.0);
// specular
DVector3 R = DVector3.Reflect(-L, normal);
R /= R.GetLength();
DVector3 S = new DVector3(0.0, 0.0, CameraZPosition) - pos;
S /= S.GetLength();
double SRcos = DVector3.DotProduct(R, S);
double SpecularComponent = Il * Ks * Math.Pow(Clamp(SRcos, 0.0, 1.0), Ip) / (K + distance);
double result = AmbientComponent + DiffuseComponent + SpecularComponent;
//if(result >= 1.0)
//{
// R /= R.GetLength();
//}
cr = Clamp((int)(255 * result * LightColor.X * ObjectColor.X), 0, 255);
cg = Clamp((int)(255 * result * LightColor.Y * ObjectColor.Y), 0, 255);
cb = Clamp((int)(255 * result * LightColor.Z * ObjectColor.Z), 0, 255);
}