// Check if two bounding spheres intersect
public static bool IntersectTest(BoundingSphere a, BoundingSphere b)
{
Vec3 dist = b.center - a.center;
double radius = a.radius + b.radius;
return (dist.ComputeMagnitudeSquared() < radius * radius);
}
// Return a BoudingSphere which fully contains the specified bounding sphere and vertex
// Like Combine, but simpler because the added point hasn't got a radius
public static BoundingSphere Expand(BoundingSphere a, Vec3 b)
{
Vec3 dif = b - a.center;
double distance = dif.ComputeMagnitude();
// degenerate cases... one sphere completely inside the other
if (a.radius > distance)
return new BoundingSphere { center = a.center, radius = a.radius };
// otherwise some actual work must be done... not too bad though
double radius = (distance + a.radius) * 0.5;
Vec3 center = a.center + Vec3.Normalize(dif, radius - a.radius);
return new BoundingSphere { center = center, radius = radius };
}