基金国家“八六三”高技术研究发展计划基金项目（2004AA84ts03）浙江省科学技术厅基金项目（2004C31018）Interactive design and editing of curve surface is the kernel problem of surface modeling system, Nowadays, the surfaces needed for practice use are more and more complex, If the control point of surface are modified one by one by conventional methods, it is miscellaneous and time consuming and even difficult to obtain expeeted result. Barr introduced the deformation ideology into geometry modeling area in SIGGRAPH＇ 1984. Several deformation types such as tapering, scaling, twisting and bending that are described in mechanics are defined with mathematic denotation, Afterward, many researchers began to engage in exploring how to fuse the deformation modeling method with the traditional CAD/CAM system, and how to achieve free-form deformation, In 1986, Sederberg and Parry put forward a new deformation algorithm named free-form deformation （FFD for short）.
Combining surface deformation with metaball technology, a constrained surface geometry deformation model is presented in this paper. It can not only control the scope of deformation effect but also produce abundant continuous shapes by adjusting few parameters, The method is independent of the expression of surface, and the mathematic calculation is simple. It has a wide application foreground, The work in this paper is supported by the National High-Tech Research and Development Program （863 Program No 2004AA84ts03） of China, and the Science and Technology Committee of Zhejiang Province （No. 2004C31018）.