Talk Title: From trimmed NURBS to watertight boundary representations of CAD models
A fundamental problem in Geometric Modeling is the one of converting the representation of a solid from one (representation) form to another. In this talk, I will discuss a particular instance of this problem, namely, the conversion of boundary representations of CAD models from the trimmed Non-Uniform Rational B-Splines (NURBS) form to watertight parametric forms. For historical and for practical reasons, the geometry of CAD models have been represented by trimmed NURBS. While this representation form is often more convenient to control a signature piece of the boundary in isolation, it is in general very difficult or impossible to represent the entire boundary as a watertight surface. In other words, the trimmed NURBS surface patches may not join each other continuously, giving rise to a boundary representation with very small gaps (i.e., fillets) along the boundary curves of the trimmed patches. With the advent and recent progress of Iso-Geometric Analysis (IGA), the need for watertight boundary representations of CAD models prompted several researchers to pay close attention to the conversion problem again. The aim of my talk is two-fold. First, I will focus on the shortcomings of the most recent solutions to the conversion problem from an industry's perspective. Second, I will shed some light on what constitutes a good solution to the problem. The talk is related to an on-going research collaboration with Jörg Peters (UF, United States) and Paulo Pagliosa (UFMS, Brazil).
Marcelo Siqueira received the BSc (computer science), in 1992, from Universidade Federal do Rio Grande do Norte (UFRN). He received the master degree, in 1994, from Universidade de São Paulo (USP), and the PhD degree, in 2006, from the University of Pennsylvania (UPenn). From 1996 to 2008, he was a professor at the College of Computing of Universidade Federal de Mato Grosso do Sul (UFMS). From 2009 to 2017, he was a professor at the Department of Mathematics of UFRN. In 2017, he joined Velo3D, a startup located at Campbell, CA, USA, that developed a disruptive technology for 3d printing of metallic parts. In 2018, he joined Align Technology, the world leader of clear aligners for orthodontic therapy, where is currently a full-time researcher and software developer. His research interests are mesh generation, modeling of curves and surfaces, and digital topology.