仁gma5tmar HALSTEAD, M., KASS, M., AND DEROSE, T. 1993. Efficient, fair interpolation using Catmull-Clark surfaces. In Proceedings of SIGGRAPH 93, ACM, 35–44. HOPPE, H., DEROSE, T., DUCHAMP, T., HALSTEAD, M., JIN, H., MCDONALD, J., SCHWEITZER, J., AND STUETZLE, W. 1994. Piecewise smooth surface reconsruction. In Proceedings of SIGGRAPH 94, ACM, 295–302. HUANG, Z., WANG, G., AND YUE, W. 2006. Optimization based subdivision depth computation for extra-ordinary Catmull￾Clark subdivision surface patches. Submitted, available at http://graphics.pku.edu.cn/hzj. LOOP, C. T. 1987. Smooth subdivision surfaces based on triangles. Master’s thesis, Department of Mathematics, University of Utah. STAM, J. 1998. Exact evaluation of Catmull-Clark subdivision surfaces at arbitrary parameter values. In Proceedings of SIG￾GRAPH 98, Annual Conference Series, ACM, 395–404