Edelsbrunner, HerbertMathieu Desbrun and Helmut Pottmann2014-01-292014-01-2920053-905673-24-X1727-8384https://doi.org/10.2312/SGP/SGP05/009-011A challenging problem in computer-aided geometric design is the decomposition of a surface into four-sided regions that are then represented by NURBS patches. There are various approaches published in the literature and implemented as commercially available software, but all fall short in either automation or quality of the result. At Raindrop Geomagic, we have recently taken a fresh approach based on concepts from Morse theory. This by itself is not a new idea, but we have some novel ingredients that make this work, one being a rational notion of hierarchy that guides the construction of a simplified decomposition sensitive to only the major critical points.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Boundary representations, Hierarchy and geometric transformations