计算三角形的包围球

void MinimumBoundingCircle(Circle &circle, Point a, Point b, Point c) { float dotABAB = Dot(b - a, b - a); float dotABAC = Dot(b - a, c - a); float dotACAC = Dot(c - a, c - a); float d = 2.0f*(dotABAB*dotACAC - dotABAC*dotABAC); Point referencePt = a; if (Abs(d) <= EPSILON) { // a, b, and c lie on a line. Circle center is center of AABB of the // points, and radius is distance from circle center to AABB corner AABB bbox = ComputeAABB(a, b, c); circle.c = 0.5f * (bbox.min + bbox.max); referencePt = bbox.min; } else { float s = (dotABAB*dotACAC - dotACAC*dotABAC) / d; float t = (dotACAC*dotABAB - dotABAB*dotABAC) / d; // s controls height over AC, t over AB, (1-s-t) over BC if (s <= 0.0f) { circle.c = 0.5f * (a + c); } else if (t <= 0.0f) { circle.c = 0.5f * (a + b); } else if (s + t >= 1.0f) { circle.c = 0.5f * (b + c); referencePt = b; } else circle.c = a + s*(b - a) + t*(c - a); } circle.r = Sqrt(Dot(circle.c - referencePt, circle.c - referencePt)); }