In existing CAD systems

classical NURBS patch method is used to build solids of irregular topology with some drawbacks: difficult patching-up and trimming

expensive computing and hard exact representing. However

in practical engineering application

there are many solids with complex shape

which require smooth ness and are difficult to be combined with basic elements. Subdivision modeling is a new and easily computing method

and can represent arbitrary topology

which has been widely researched in CAD. In this paper

the principles and methods of surface subdivision are described

and the kernel technologies for subdivision including mesh creation

boundary control

normal control

transformation from subdivision mesh to NURBS patch

Boolean calculation

etc.

are studied. A scheme of using subdivision modeling in existing CAD system is presented

and a prototyping system of subdivision modeling is constructed. The experiment proves that by using this scheme

the modeling time is shortened and the efficiency is improved.