This is kind of the inversion of the mesh decimation project. Sometimes, there is a need for adding more details. For instance, adding details around a certain part of a human body such as the face for facial expressions. This subdivision scheme makes use of the curvature of a certain vertex. Simply adding a vertex between two vertices really does nothing except add extra complexity to the mesh. Sometimes you want some features to stay sharp. Therefore I added a way to flag some polygons as “important” so that the region in which they are present would not be subdivided.