The patch system supports any combination of quadrilateral and triangular patches, as long as they are set up so that a single edge is only shared by at most two patches.

Adjacent patches share control points and vectors on their common edges. This minimizes the amount of data and makes book keeping easier. It also guarantees matching patch edges.

The only problem with this system is that the 3ds Max quad patches are bicubic (degree 3), and if they are connected to degree 3 triangular patches, discontinuities will result at the boundaries. The solution used in 3ds Max is to store the patch information and allow users to manipulate it in a degree-3 manner (4 points on the side of a patch). When we go to interpolate it, however, we convert all the triangular patches' control points to degree 4, where they can be completely compatible with their quad neighbors.