Multimedia Systems (2006) 11(5): 480–494 DOI 10.1007/s00530-006-0017-1 REGULAR PAPER Hung-Kuang Chen · Chin-Shyurng Fahn · Jeffrey J. P. Tsai · Rong-Ming Chen · Ming-Bo Lin Generating high-quality discrete LOD meshes for 3D computer games in linear time Published online: 24 March 2006 c  Springer-Verlag 2006 Abstract The real-time interactive 3D multimedia applica- tions such as 3D computer games and virtual reality (VR) have become prominent multimedia applications in recent years. In these applications, both visual fidelity and degree of interactivity are usually crucial to the success or fail- ure of employment. Although the visual fidelity can be in- creased using more polygons for representing an object, it takes a higher rendering cost and adversely affects the rendering efficiency. To balance between the visual quality and the rendering efficiency, a set of level-of-detail (LOD) meshes has to be generated in advance. In this paper, we propose a highly efficient polygonal mesh simplification al- gorithm that is capable of generating a set of high-quality discrete LOD meshes in linear run time. The new algorithm adopts memoryless vertex quadric computation, and sug- gests the use of constant size replacement selection min- heap, pipelined simplification, two-stage optimization, and a new hole-filling scheme, which enable it to generate very high-quality LOD meshes using relatively small amount of main memory space in linear runtime. Keywords Interactive 3D multimedia · Computer game · Virtual reality · Mesh simplification · Level-of-detail mesh · Iterative full-edge collapse H.-K. Chen (B ) · M.-B. Lin Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, R.O.C. E-mail: hank@asia.edu.tw, mblin@et.ntust.edu.tw H.-K. Chen · R.-M. Chen Department of Information and Design, Asia University, Taichung, Taiwan, R.O.C. E-mail: rmchen@asia.edu.tw C.-S. Fahn Department of Computer Science and Information Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, R.O.C. J. J. P. Tsai Department of Computer Science, University of Illinois at Chicago, U.S.A. E-mail: tsai@cs.uic.edu 1 Introduction The polygonal mesh has been the major representation scheme of the 3D objects in interactive 3D multimedia appli- cations such as 3D computer games and virtual reality (VR) that has become one of the most popular multimedia applica- tions in recent years [1]. Essentially, both the visual fidelity and degree of interactivity play important roles in such ap- plications. Since the objects are represented by a polygonal mesh, the increase of visual fidelity usually raises the render- ing cost by using more polygons, which adversely influences the rendering efficiency. To trade off between the visual fi- delity and interactivity, the level-of-detail (LOD) technique is commonly employed to adaptively adjust the resolution of the objects by selecting from a set of pre-built LOD meshes according to their importance [2]. To fill such need, the 3D objects are usually pre- converted into a set of different resolution meshes by a polygonal mesh simplification algorithm before their use. Figure 1 shows an example of the LOD meshes in which the resolution of the Dragon meshes are decreased in propor- tion to the distance from the viewer. In the figure, four LOD meshes comprising 27 K, 8.8 K, 3 K, and 1 K triangles are placed from near to far to the viewer where one can hardly tell the differences between these rendered images. Besides the contributions to interactivity, the quality of the resulting LOD meshes has great importance to the visual fidelity. Significant shape features such as horns, claws, and tails may be lost if a low-quality simplification algorithm Fig. 1 The LOD control of the Dragon mesh according to the distance from the viewer