［1］Blinn J F. A generalization ofalgebraic surface drawing. ACM Transac tions on Graphics, 1982, 1(3):235～256.
[2]
［3］Wyvill G, McPheeters C, Wyvill B. Data structure for softobjects. The VisualComputer, 1986,2(4):227～ 234.
[3]
［5］Bloomenthal J, Wyvill B. Interactive techni ques for implicitmodeling. ComputerGraphics, 1990,24(2):109～1 16.
[4]
［7］Jin Xiaogang, Li Y F, Peng Qunsheng. Ge neral constraineddeformation based ongeneralized metaballs. Computers & Graphics, 2000,24(2):219～231.
[5]
［9］Bloomenthal J, Shoemake K. Convolution su rface. ComputerGraphics, 1991,25(4): 251～256.
[6]
［11］McCormack J, Sherstyuk A. Creating and rendering convolution surfaces. C omputerGraphics Forum, 1998,17(2):113～120.
[7]
［13］Bloomenthal J. Polygonization of implicit surfaces. Computer Aided Geome tricDesign, 1988,5(4):341～355.
[8]
［14］Bolton K M. Biarc curves. Computer Aided Design, 1975,7:89～92.
[9]
［16］Su B Q, Liu D Y. Computational Geometry, Academic Press, New York, USA, 1989.
[10]
［2］Nishimura H, Hirai M, Kawai T. Object m odeling bydistribution function a nd amethod of image generation. Transactions on IECE, 1985, 68-D(4):718～725.
[11]
［4］Wyvill B, Wyvill G. Field functions for implicit surfaces. The Visual Compute r,1989,5(1/2):75～82.
[12]
［6］Bao Hujun, Jin Xiaogang, Peng Qunsheng. Constraineddeformations based on metaballs.Chinese Journal o f Advanced Software Research, 1999,6(3):211～217.
[13]
［8］Frisken S F, Perry R N, Rockwood A P et al. Adaptivelysampled distance f ields: ageneral representation of shape for computer graphics. In: Proceedings of Siggraph\'2000,edited by Akeley K, New Orleans, LA, USA, 2000:249～254.
[14]
［10］Bloomenthal J. Skeletal design of natural forms [Ph.D Dissertation]. D epartmentof Computer Science, University of Calgary, Canada, 1995.
[15]
［12］Nishita T, Nakamae E. A method for displaying metaballs by using Bezier clipping.Computer Graphics Forum, 1994, 13(3):71～80.
[16]
［15］Yang X N. Approximating NURBS curves by arc splines. In: Proceedings of GeometricModeling and Processing, edited by Martin R and Wang W, Hongkong, IEEE Computer Society,2000:10～12.
