We present an algorithm for end-to-end out-of-core simplification and view-dependent visualization of large surfaces. The method consists of three phases: (1) memory insensitive simplification; (2) memory insensitive construction of a level-of-detail hierarchy; and (3) run-time, output sensitive, view-dependent rendering and navigation of the mesh. The first two off-line phases are performed entirely on disk, and use only a small, constant amount of memory, whereas the run-time component relies on memory mapping to page in only the rendered parts of the mesh in a cache coherent manner. As a result, we are able to process and visualize arbitrarily large meshes given a sufficient amount of disk space--a constant multiple of the size of the input mesh. Similar to recent work on out-of-core simplification, our memory insensitive method uses vertex clustering on a uniform octree grid to coarsen a mesh and create a hierarchy, and a quadric error metric to choose vertex positions at all levels of resolution. We show how the quadric information can be used to concisely represent vertex position, surface normal, error, and curvature information for anisotropic view-dependent coarsening and silhouette preservation. The focus of this paper is on the out-of-core construction of a level-of-detail hierarchy---our framework is general enough to incorporate many different aspects of view-dependent rendering. We therefore emphasize the off-line phases of our method, and report on their theoretical and experimental memory and disk usage and execution time. Our results indicate on average one to two orders of magnitude improvement in processing speed over previous out-of core methods. Meanwhile, all phases of the method are both disk and memory efficient, and are fairly straightforward to implement.
展开▼
