Mesh refinement with color attributes

Although many sophisticated solutions have been proposed to reduce the geom etry complexity of a 3D mesh, few of these take into account color and text ure fields, which are fundamental for a visual appearance of high duality. We propose here an innovative solution which combines the concept of hierar chy in refining a mesh with color attributes with mesh regularization. It o perates subdividing recursively the faces of a 3D mesh, which was previousl y simplified according to geometrical criteria only. New vertices are intro duced by splitting a face until a maximum color error is achieved. The erro r is evaluated in CIE-L*u*v* iso-perceptual metric. Splitting is carried ou t using a new strategy, which chooses between either binary or quaternary s ubdivision schema, in order to achieve 3D mesh regularization. In this resp ect our method improves other hierarchical subdivision techniques (applied for example to radiosity and height fields). If the unsimplified version of the mesh is available, the procedure positions the new vertices on this me sh, decreasing, the topological error besides the color one. The method pre sented here is quite general and allows to create models of high pictorial quality ( approximate to 20,000 faces), which can be manipulated in real-ti me on machines with no hardware accelerator for texture mapping. Main stren gth of the method is locality, which allows very fast operations as well as the possibility of local refinements. Results show how, at the expense of few more polygons, the final appearance of the model can be greatly improve d in a very short time. The produced models are suitable to progressive tra nsmission: first a light mesh can be transmitted with its per-vertex colors , then, in a second stage, the position and color value of the vertices add ed in the refinement stage can be sent to improve the pictorial appearance. (C) 2001 Elsevier Science Ltd. All rights reserved.