A simple yet effective user controllable mesh simplification

Mesh simplification has become a key ingredient for real-time graphics applications. However, practitioners have found that automatic simplification methods usually fail to produce satisfactory result when models of very low polygon count are desired. This is due to the fact that existing methods take no semantic or functional metric into account, and moreover, each error metric proposed previously has its own strength and weakness. In this paper, we propose a user-controllable mesh simplification framework that allows users to achieve a predictable resolution improvement in selected regions of a simplified mesh derived by using any error metric. The framework consists of two stages. The first stage employs weighting schemes that allow users to refine unsatisfactory regions to a user-expected resolution. The second stage is a local refinement aiming to provide a user- guided fine-tune to recover local sharp features. Two weighting schemes, namely uniform weighting and nonuniform weighting, are proposed. In uniform weighting scheme, a weight value is applied to all original mesh vertices in a selected region, resulting in a uniform improvement on vertex resolution in the region, while in the nonuniform weighting scheme varying weights are applied to vertices in a selected region and obtain a nonuniform resolution improvement in the region. Different from the previous user-assisted simplification methods that reorder the collapsing sequence indirectly by weighting the collapsing cost of edges, the two proposed weighting schemes directly reorder the edge collapsing sequence, ensuring a predictable resolution improvement in the selected regions. Moreover, the proposed weighting schemes are independent on error metric used for simplification and ensure the same resolution improvement when a weighting value is applied to simplified meshes with different resolutions.