Mesh Simplification with Global Contour Feature Preservation

In architectural and mechanical engineering, man-made CAD models often have some prominent contours and regular shapes. These features are important to the visual perception. Traditional mesh simplification methods are not very suitable for this kind of models because in the simplified results some important mini structures and shape regularities are always missed. In this paper, we propose a new simplification algorithm that is tailored for man-made CAD models and can maintain the processed modelpsilas most prominent contours and the global shape features. To achieve this purpose, in the simplification process, we avoid as much as possible contracting the vertexes on those contours. At the same time, we simplify the contour curves as a whole. The algorithm proceeds as follows. Firstly, the division contours of all surfaces are detected and all component edges are subsequently classified. Secondly, targeting at minimizing the objective function of contracting vertexes along the contours, all edges are simplified by QEM (quadric error metric). In this way, the missing of important mini structures can be minimized. After this step, the intermediate simplification result is obtained, and one simplified polygon is generated for each surfacepsilas division contour. Thirdly, using those polygons as starting point, an approximation polygon for each surface contour is generated by maximizing the shape similarity between each contour and the corresponding polygon and at the same time minimizing the change of the global features of the contours. Finally, the vertexes of all those simplified polygons in the intermediate result are adjusted based on the approximated polygons to form the final simplified model, in which the polygons will guarantee the maintenance of the global shape features of the original contours. The experiments and comparisons demonstrated that, our method not only can avoid the loss of important mini structures of the original model, but also can maintain - global prominent shape features such as symmetry and edge equality, etc.