Procedural mesh features applied to subdivision surfaces using graph grammars

A typical industrial design modelling scenario involves defining the overall shape of a product followed by adding detail features. Procedural features are well-established in computer aided design (CAD) involving regular forms, but are less applicable to free-form modelling involving subdivision surfaces. Current approaches do not generate sparse subdivision control meshes as output, which is why free-form features are manually modelled into subdivision control meshes by domain experts. Domain experts change the local topology of the subdivision control mesh to incorporate features into the surface, without increasing the mesh density unnecessarily and carefully avoiding the appearance of artefacts. In this paper we show how to translate this expert knowledge to grammar rules. The rules may then be invoked in an interactive system to automatically apply features to subdivision surfaces.