Graphics Reference
In-Depth Information
return Dot(c1 - c2, c1 - c2);
}
if (a <= EPSILON) {
// First segment degenerates into a point
s = 0.0f;
t=f/e;
//s=0=>t=(b*s+f)/e=f/e
t = Clamp(t, 0.0f, 1.0f);
} else {
float c = Dot(d1, r);
if (e <= EPSILON) {
// Second segment degenerates into a point
t = 0.0f;
s = Clamp(-c / a, 0.0f, 1.0f);
//t=0=>s=(b*t-c)/a=-c/a
} else {
// The general nondegenerate case starts here
float b = Dot(d1, d2);
float denom = a*e-b*b;
// Always nonnegative
// If segments not parallel, compute closest point on L1 to L2 and
// clamp to segment S1. Else pick arbitrary s (here 0)
if (denom != 0.0f) {
s = Clamp((b*f - c*e) / denom, 0.0f, 1.0f);
} else s = 0.0f;
// Compute point on L2 closest to S1(s) using
// t = Dot((P1 + D1*s) - P2,D2) / Dot(D2,D2) = (b*s + f) / e
t=(b*s+f)/e;
// If t in [0,1] done. Else clamp t, recompute s for the new value
// of t using s = Dot((P2 + D2*t) - P1,D1) / Dot(D1,D1)= (t*b - c) / a
// and clamp s to [0, 1]
if (t < 0.0f) {
t = 0.0f;
s = Clamp(-c / a, 0.0f, 1.0f);
} else if (t > 1.0f) {
t = 1.0f;
s = Clamp((b - c) / a, 0.0f, 1.0f);
}
}
}
c1=p1+d1*s;
c2=p2+d2*t;
return Dot(c1 - c2, c1 - c2);
}
