{
float t0, t1; // solutions for t if the ray intersects
#if 0
// geometric solution
Vec3f L = center - orig;
float tca = L.dotProduct(dir);
// if (tca < 0) return false;
float d2 = L.dotProduct(L) - tca * tca;
if (d2 > radius2) return false;
float thc = sqrt(radius2 - d2);
t0 = tca - thc;
t1 = tca + thc;
#else
// analytic solution
Vec3f L = orig - center;
float a = dir.dotProduct(dir);
float b = 2 * dir.dotProduct(L);
float c = L.dotProduct(L) - radius2;
if (!solveQuadratic(a, b, c, t0, t1)) return false;
#endif
if (t0 > t1) std::swap(t0, t1);
if (t0 < 0) {
t0 = t1; // if t0 is negative, let's use t1 instead
if (t0 < 0) return false; // both t0 and t1 are negative
}
t = t0;
return true;
}
我认为在Three.js中,由于大多数材质都由小三角形组成,每个射线投射计算都依赖于三角形射线投射。