The CollisionWorld object inside MoveIt! is used to find collisions inside a planning scene, which are using the Flexible Collision Library (FCL) package as a backend. MoveIt! supports collision checking for different types of objects, such as meshes; primitive shapes such as boxes, cylinders, cones, spheres, and so on; and Octomap.

Collision checking is one of the most computationally expensive tasks during motion planning. To reduce this computation, MoveIt! provides a matrix called Allowed Collision Matrix (ACM). It contains a binary value corresponding to the need to check for collisions between two pairs of bodies. If the value of the matrix is 1, it means that the collision of the corresponding pair is not needed. We can set the value to 1, where the bodies are always so far away that they will never collide with each other. Optimizing ACM can reduce the total computation needed for collision avoidance. This was done when we were creating the package, as you may remember!