Along with motion planning and IK solving algorithm, one of the important tasks that is done in parallel in MoveIt! is collision checking and its avoidance. The collision can be self collision or environmental collision. MoveIt! can handle both the environment collision and the self collision. The MoveIt! package is inbuilt with FCL (Flexible Collision Library) (http://gamma.cs.unc.edu/FCL/fcl_docs/webpage/generated/index.html), which is an open source project that implements various collision detection and avoidance algorithms. MoveIt! takes the power of FCL and handles collision inside planning scene using a collision_detection::CollisionWorld class. The MoveIt! collision checking includes objects such as meshes, primitives shapes such as boxes and cylinders, and OctoMap. The OctoMap (http://octomap.github.io/) library implements a 3D occupancy grid called octree that consists of probabilistic information of obstacles in the environment. The MoveIt! package can build an OctoMap using 3D point cloud information and can directly feed the OctoMap to FCL for collision checking.

Similar to motion planning, collision checking is also very computationally intensive. We can fine tune the collision checking between two bodies, say a robot link or with the environment, using a parameter called ACM (Allowed Collision Matrix). If the value of a collision between two links is set to 1 in ACM, there will not be any collision checks. We may set this for links that are far from each other. We can optimize the collision checking process by optimizing this matrix.