private float brdf(Vector3 i, Vector3 o, OrthoNormalBasis basis)
{
float fr = 4 * (float)Math.PI * alphaX * alphaY;
float p = basis.untransformZ(i) * basis.untransformZ(o);
if (p > 0)
{
fr *= (float)Math.Sqrt(p);
}
else
{
fr = 0;
}
Vector3 h = Vector3.add(i, o, new Vector3());
basis.untransform(h);
float hx = h.x / alphaX;
hx *= hx;
float hy = h.y / alphaY;
hy *= hy;
float hn = h.z * h.z;
if (fr > 0)
{
fr = (float)Math.Exp(-(hx + hy) / hn) / fr;
}
return(fr);
}
public Color GetRadiance(ShadingState state)
{
// make sure we are on the right side of the material
state.faceforward();
OrthoNormalBasis onb = state.getBasis();
// direct lighting and caustics
state.initLightSamples();
state.initCausticSamples();
Color lr = Color.black();
// compute specular contribution
if (state.includeSpecular)
{
Vector3 inv = state.getRay().getDirection().negate(new Vector3());
foreach (LightSample sample in state)
{
float cosNL = sample.dot(state.getNormal());
float fr = brdf(inv, sample.getShadowRay().getDirection(), onb);
lr.madd(cosNL * fr, sample.getSpecularRadiance());
}
// indirect lighting - specular
if (numRays > 0)
{
int n = state.getDepth() == 0 ? numRays : 1;
for (int i = 0; i < n; i++)
{
// specular indirect lighting
double r1 = state.getRandom(i, 0, n);
double r2 = state.getRandom(i, 1, n);
float alphaRatio = alphaY / alphaX;
float phi = 0;
if (r1 < 0.25)
{
double val = 4 * r1;
phi = (float)Math.Atan(alphaRatio * Math.Tan(Math.PI / 2 * val));
}
else if (r1 < 0.5)
{
double val = 1 - 4 * (0.5 - r1);
phi = (float)Math.Atan(alphaRatio * Math.Tan(Math.PI / 2 * val));
phi = (float)Math.PI - phi;
}
else if (r1 < 0.75)
{
double val = 4 * (r1 - 0.5);
phi = (float)Math.Atan(alphaRatio * Math.Tan(Math.PI / 2 * val));
phi += (float)Math.PI;
}
else
{
double val = 1 - 4 * (1 - r1);
phi = (float)Math.Atan(alphaRatio * Math.Tan(Math.PI / 2 * val));
phi = 2 * (float)Math.PI - phi;
}
float cosPhi = (float)Math.Cos(phi);
float sinPhi = (float)Math.Sin(phi);
float denom = (cosPhi * cosPhi) / (alphaX * alphaX) + (sinPhi * sinPhi) / (alphaY * alphaY);
float theta = (float)Math.Atan(Math.Sqrt(-Math.Log(1 - r2) / denom));
float sinTheta = (float)Math.Sin(theta);
float cosTheta = (float)Math.Cos(theta);
Vector3 h = new Vector3();
h.x = sinTheta * cosPhi;
h.y = sinTheta * sinPhi;
h.z = cosTheta;
onb.transform(h);
Vector3 o = new Vector3();
float ih = Vector3.dot(h, inv);
o.x = 2 * ih * h.x - inv.x;
o.y = 2 * ih * h.y - inv.y;
o.z = 2 * ih * h.z - inv.z;
float no = onb.untransformZ(o);
float ni = onb.untransformZ(inv);
float w = ih * cosTheta * cosTheta * cosTheta * (float)Math.Sqrt(Math.Abs(no / ni));
Ray r = new Ray(state.getPoint(), o);
lr.madd(w / n, state.traceGlossy(r, i));
}
}
lr.mul(rhoS);
}
// add diffuse contribution
lr.add(state.diffuse(getDiffuse(state)));
return(lr);
}