The leaves of the tree are labelled 'in' or 'out'. These schemata work either by grids or octrees. Grid schemata subdivide space in conformance with a grid system. The elements of the grid are typically hexahedra. Octree schemata recursively divide a cube into eight further cubes.
Grey cubes are sub-divided.
A solid model which deals with an object by describing its physical boundaries. CAD Computer-Aided Design. The use of computers to help in design work, for example by architects. The emphasis is on visual information. CAE Computer-Aided Engineering.