Does collision-checking use an approximate or exact algorithm to check collision between two shapes?

[ghost]

I tried your library to check the collision between two ellipsoids. It works well in cases where both ellipsoids have a large overlap but it fails to detect a collision when both barely overlap. I confirmed this by plotting the ellipsoids in 3D and noticing that they overlap a bit. It is small but not negligible.

However, fcl seems to not detect the collision. So, I can only assume that you guys are using an approximate algorithm. Is there a way to force your library to use an exact algorithm? Or maybe I can change some parameters in your collision check algorithm to make it work for my case?