NSA simplification algorithm: geometrical vs. visual quality

The model simplification algorithms have a great interest in a variety of areas, since it allow the replacement of large models by approximations with far fewer cells for manipulation and visualization purposes. The quality of the simplified models and the execution times are the main aspects to distinguish the algorithms. Normally the quality evaluation is based on the analysis of geometrical errors of the simplified models but it is not enough to evaluate the visual quality of simplified models. This paper presents a edge collapsing-based simplification algorithm, called NSA, for polygonal models that is faster than the other algorithms found in the literature that use the edge collapse operation. However it makes a good trade-off between time performance and mesh quality. Besides, in some cases, the visual quality of simplified models created by NSA algorithm is superior to the visual quality of simplified models created by other algorithms, particularly for models that have planar zones (CAD models). Some results are compared between NSA and QSlim algorithms to illustrate the geometrical and visual quality of simplified models.