Luiz Velho Ken Perlin Lexing Ying Henning Biermann Procedural Shape Synthesis on Subdivision Surfaces. 146-153 2001 conf/sibgrapi/2001 SIBGRAPI http://dlib2.computer.org/conferen/sibgrapi/1330/pdf/13300146.pdf db/conf/sibgrapi/sibgrapi2001.html#VelhoPYB01