/// <summary>
/// Discrete Circle vs Circle test. Very fast. Generates contact info.
/// NOTE: check distance for collisions. If negative then a collision has occurred.
/// This is done to remove all branches from this test and leave it to the user to decide when to branch.
/// </summary>
public static void CircleCircleTest(JVector centerA, float radiusA, JVector centerB, float radiusB, out JVector pointA, out JVector pointB, out JVector normal, out float distance)
{
// ||A-B|| - (r1+r2) < 0
float d = JVector.DistanceSquared(centerA, centerB);
float r = (radiusA + radiusB);
r *= r;
distance = d - r;
normal = (centerA - centerB) / d;
normal.Normalize();
// calculate closest 2 points
pointA = JVector.Negate(normal) * radiusA + centerA;
pointB = normal * radiusB + centerB;
}