Multiresolution rendering by sewing trimmed NURBS surfaces

Abstract

Most of the industrial parts are designed as trimmed NURBS. For their efficient rendering multiresolution models are needed. To create such models without artifacts at the trimming curves, one needs to sew parts together along the common boundaries. Due to the problem of determining the geometric places in 3D space along the trimming curves where sewing should be done, current approaches need to have a priori neighbourhood information of the patches and this way they do not provide an automatic solution to create large connected models just from a set of surfaces. In this paper we describe a method, which automatically determines common boundaries of trimmed NURBS surfaces and sews along them. Such a method provides us a non-manifold or manifold structure, which can be handled using standard multi-resolution techniques. Several examples of industrial data demonstrate the efficiency and applicability of our new method. The introduced techniques will also be included into the OpenSG scenegraph API [8] as the basic tool for NURBS rendering.