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surface
hmatte(
float Ka = 0.05,
Kd = 1;
)
{
float Lhw,Nhw; /* w-cord of hyperbolic normal vector to P */
point Nh, Lh; /* first 3 cords of hyperbolic normal vector to P */
point Px;
float b,d,nn;
Nh = faceforward(normalize(N),I);
Px = transform("shader",P);
/* compute plane equation */
Ci = 0;
illuminance(Px)
{
Nhw = Px.Nh;
b = -(L.Px - 0)/(Px.Px - 1);
Lh = L + b*Px; /* hyperbolic light vector is lin comb of L,P */
Lhw = 0 + b;
d = (Lh.Nh - Lhw*Nhw)/sqrt(abs((Lh.Lh - Lhw*Lhw)*(Nh.Nh - Nhw*Nhw)));
if (d < 0.0) d = -d;
if (d > 1.0) {
/*
printf("Light:%f %f %f %f\n",xcomp(Lh),ycomp(Lh),zcomp(Lh),Lhw);
printf("Normal:%f %f %f %f\n",xcomp(Nh),ycomp(Nh),zcomp(Nh),Nhw);
printf("Posi:%f %f %f 1.0\n",xcomp(Px),ycomp(Px),zcomp(Px));
*/
d = 1.0;
}
Ci += Os * Cs * (Ka*ambient() + Cl*Kd*d );
}
Oi = Os;
}
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