FCL is a library for performing three types of proximity queries on a pair of geometric models composed of triangles.

Collision detection: detecting whether the two models overlap, and optionally, all of the triangles that overlap.
Distance computation: computing the minimum distance between a pair of models, i.e., the distance between the closest pair of points.
Tolerance verification: determining whether two models are closer or farther than a tolerance distance.
Continuous collision detection: detecting whether the two moving models overlap during the movement, and optionally, the time of contact.
Contact information: for collision detection and continuous collision detection, the contact information (including contact normals and contact points) can be returned optionally.