Louis Feng Ingrid Hotz Bernd Hamann Kenneth I. Joy Anisotropic Noise Samples. 342-354 2008 14 IEEE Trans. Vis. Comput. Graph. 2 http://dx.doi.org/10.1109/TVCG.2007.70434 db/journals/tvcg/tvcg14.html#FengHHJ08