bool CircleSegmentIntersect(CL_Vec2f C, float r, CL_Vec2f A, CL_Vec2f B, CL_Vec2f& P)
{
CL_Vec2f AC = C - A;
CL_Vec2f AB = B - A;
float ab2 = AB.dot(AB);
float acab = AC.dot(AB);
float t = acab / ab2;
if (t < 0.0f)
t = 0.0f;
else if (t > 1.0f)
t = 1.0f;
P = A + AB * t;
CL_Vec2f H = P - C;
float h2 = H.dot(H);
float r2 = r * r;
if(h2 > r2)
return false;
else
return true;
}
bool IntersectRaySphere(CL_Vec2f p, CL_Vec2f d, rtCircle s, float &t, CL_Vec2f &q)
{
CL_Vec2f m = p - s.c;
float b = m.dot(d);
float c = m.dot(m) - s.r * s.r;
// Exit if r’s origin outside s (c > 0) and r pointing away from s (b > 0)
if (c > 0.0f && b > 0.0f) return false;
float discr = b*b - c;
// A negative discriminant corresponds to ray missing sphere
if (discr < 0.0f) return false;
// Ray now found to intersect sphere, compute smallest t value of intersection
t = -b - sqrt(discr);
// If t is negative, ray started inside sphere so clamp t to zero
if (t < 0.0f) t = 0.0f;
q=p+(d*t);
return true;
}