A free shape 3d modeling system for creative design based on modified catmull-clark subdivision

How to express the designer’s creative intent in a simple and intuitive way is the main problem in 3d modeling, especially for novice designers. This paper presents a free shape 3d modeling system for creative design based on modified Catmull-Clark subdivision. The system contains a series of easy but novel operations which can be used to change the topology of models, such as creating holes and handles. In order to create sharp features, feature marking operations are provided to specify where the sharp feature is. This system also provides surface conversion function to make the modeling results be compatible with the traditional CAD systems. Firstly, a simple but efficient quad domain division scheme is adopted to generate quad sub-meshes. In order to improve the smoothness at the regular vertices, long boundary curves which across multiple sub-meshes are used to be the boundary constraints while fitting. In this way, the smoothness at regular vertex can be C² continuous. We perform experiments for both skilled and novice designers. Results show that our system is easy to operate and can be used to construct complex models with less time.