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);
}
private void initSunSky()
{
// perform all the required initialization of constants
sunDirWorld.normalize();
sunDir = basis.untransform(sunDirWorld, new Vector3());
sunDir.normalize();
sunTheta = (float)Math.Acos(MathUtils.clamp(sunDir.z, -1, 1));
if (sunDir.z > 0)
{
sunSpectralRadiance = computeAttenuatedSunlight(sunTheta, turbidity);
// produce color suitable for rendering
sunColor = RGBSpace.SRGB.convertXYZtoRGB(sunSpectralRadiance.toXYZ().mul(1e-4f)).constrainRGB();
}
else
{
sunSpectralRadiance = new ConstantSpectralCurve(0);
}
// sunSolidAngle = (float) (0.25 * Math.PI * 1.39 * 1.39 / (150 * 150));
float theta2 = sunTheta * sunTheta;
float theta3 = sunTheta * theta2;
float T = turbidity;
float T2 = turbidity * turbidity;
double chi = (4.0 / 9.0 - T / 120.0) * (Math.PI - 2.0 * sunTheta);
zenithY = (4.0453 * T - 4.9710) * Math.Tan(chi) - 0.2155 * T + 2.4192;
zenithY *= 1000; /* conversion from kcd/m^2 to cd/m^2 */
zenithx = (0.00165 * theta3 - 0.00374 * theta2 + 0.00208 * sunTheta + 0) * T2 + (-0.02902 * theta3 + 0.06377 * theta2 - 0.03202 * sunTheta + 0.00394) * T + (0.11693 * theta3 - 0.21196 * theta2 + 0.06052 * sunTheta + 0.25885);
zenithy = (0.00275 * theta3 - 0.00610 * theta2 + 0.00316 * sunTheta + 0) * T2 + (-0.04212 * theta3 + 0.08970 * theta2 - 0.04153 * sunTheta + 0.00515) * T + (0.15346 * theta3 - 0.26756 * theta2 + 0.06669 * sunTheta + 0.26688);
perezY[0] = 0.17872 * T - 1.46303;
perezY[1] = -0.35540 * T + 0.42749;
perezY[2] = -0.02266 * T + 5.32505;
perezY[3] = 0.12064 * T - 2.57705;
perezY[4] = -0.06696 * T + 0.37027;
perezx[0] = -0.01925 * T - 0.25922;
perezx[1] = -0.06651 * T + 0.00081;
perezx[2] = -0.00041 * T + 0.21247;
perezx[3] = -0.06409 * T - 0.89887;
perezx[4] = -0.00325 * T + 0.04517;
perezy[0] = -0.01669 * T - 0.26078;
perezy[1] = -0.09495 * T + 0.00921;
perezy[2] = -0.00792 * T + 0.21023;
perezy[3] = -0.04405 * T - 1.65369;
perezy[4] = -0.01092 * T + 0.05291;
int w = 32, h = 32;
imageHistogram = new float[w][];
for (int i = 0; i < imageHistogram.Length; i++)
{
imageHistogram[i] = new float[h];
}
colHistogram = new float[w];
float du = 1.0f / w;
float dv = 1.0f / h;
for (int x = 0; x < w; x++)
{
for (int y = 0; y < h; y++)
{
float u = (x + 0.5f) * du;
float v = (y + 0.5f) * dv;
Color c = getSkyRGB(getDirection(u, v));
imageHistogram[x][y] = c.getLuminance() * (float)Math.Sin(Math.PI * v);
if (y > 0)
{
imageHistogram[x][y] += imageHistogram[x][y - 1];
}
}
colHistogram[x] = imageHistogram[x][h - 1];
if (x > 0)
{
colHistogram[x] += colHistogram[x - 1];
}
for (int y = 0; y < h; y++)
{
imageHistogram[x][y] /= imageHistogram[x][h - 1];
}
}
for (int x = 0; x < w; x++)
{
colHistogram[x] /= colHistogram[w - 1];
}
jacobian = (float)(2 * Math.PI * Math.PI) / (w * h);
}
public Color GetRadiance(ShadingState state)
{
// lookup texture based on ray direction
return(state.includeLights ? getColor(basis.untransform(state.getRay().getDirection(), new Vector3())) : Color.BLACK);
}