private double lambert2(Vector light, Vector normal, double brilliance)
{
return Math.Pow(Math.Abs(light.Dot(normal) / light.Length), brilliance);
}
private void CalculateLightContrib(Vector normal, ColorIntensity lightColor, Material surf, ColorIntensity pigment, ref double rI, ref double gI, ref double bI, Vector lightdir, Vector eye)
{
double diffusivity = 1.0-surf.Specularity;
if (surf.Phong > 0.0)
{
Vector reflection = eye;
reflection.Add(normal.Scale(-2.0 * eye.Dot(normal)));
double phong = -lightdir.Scale(1.0 / lightdir.Length).Dot(reflection);
if (phong > 0.0)
{
double phongpowd = Math.Pow(phong, surf.Exponent);
rI += surf.Phong * phongpowd * lightColor.R*diffusivity;
gI += surf.Phong * phongpowd * lightColor.G * diffusivity;
bI += surf.Phong * phongpowd * lightColor.B * diffusivity;
}
}
if (surf.Specular > 0.0)
{
Vector half = lightdir.Scale(1.0 / lightdir.Length);
half.Add(eye);
half.ScaleSelf(0.5);
double spec = half.Dot(normal) / half.Length;
if (spec > 0.0)
{
double specpowd = Math.Pow(spec, 1.0 / surf.Roughness);
rI += surf.Specular * specpowd * lightColor.R * diffusivity;
gI += surf.Specular * specpowd * lightColor.G * diffusivity;
bI += surf.Specular * specpowd * lightColor.B * diffusivity;
}
}
if (surf.Iridescence > 0.0)
{
double cosaoi = lightdir.Dot(normal)/lightdir.Length;
double interference = 4.0 * Math.PI * surf.FilmThickness * cosaoi;
double intensity = cosaoi * surf.Iridescence;
double rwl = 0.25;
double gwl = 0.18;
double bwl = 0.14;
/* Modify color by phase offset for each wavelength. */
rI += surf.Iridescence * (intensity * (1.0 - 0.5 * Math.Cos(interference / rwl))) * diffusivity;
gI += surf.Iridescence * (intensity * (1.0 - 0.5 * Math.Cos(interference / gwl))) * diffusivity;
bI += surf.Iridescence * (intensity * (1.0 - 0.5 * Math.Cos(interference / bwl))) * diffusivity;
}
double lam = lambert2(lightdir, normal, surf.Brilliance);
rI += surf.Diffuse * pigment.R * lam * lightColor.R * diffusivity;
gI += surf.Diffuse * pigment.G * lam * lightColor.G * diffusivity;
bI += surf.Diffuse * pigment.B * lam * lightColor.B * diffusivity;
}