Figure 1: Collision detection in a thin-shell simulation. Given a control mesh of a bent tube, our algorithm identifies interfering regions on the limit surface up to a user-specified precision. Above, we have resolved interference with progressively increasing precision. AbstractSubdivision surfaces are an attractive representation when modeling arbitrary topology free-form surfaces and show great promise for applications in engineering design [5,6] and computer animation [10]. Interference detection is a critical tool in many of these applications. In this paper we derive normal bounds for subdivision surfaces and use these to develop an efficient algorithm for (self-) interference detection.