Visualization of CAD Models

3D models today are used in many areas, e.g. computer-aided geometric design, animation, and computer games. The areas have different demands; computer-aided geometric design must have exact models, cartoons must look good and games must have real-time feedback. Computer-aided design software commonly uses trimmed NURBS as primitives, which have some support in low level graphic visualization libraries such as OpenGL. Animators prefer subdivision surfaces because of their greater flexibility and ability to avoid gaps. However, subdivision surfaces have today limited API support. Mathematically, NURBS is the standard way to represent smooth surfaces. However, NURBS has problems with gaps along borders and they cannot represent surfaces of arbitrary topology. On the other hand, subdivision surfaces have problems with standardization, since there are multiple choices of schemes to use. This report shows that subdivision surfaces are superior to trimmed NURBS for modeling and visualization of composite surfaces.