Origin brush

An origin brush is just a brush (usually a simple box shape) with the texture "origin". Such a brush is used to define the anchor point of entities like e.g. a train or a rotating door.

The origin brush must be part of the entity to fulfill its function.

The software determines the origin defined by that brush by calculating its three-dimensional center. So, the center of the origin brush is the anchor point of the entity that uses the origin brush.