A framework for memory-efficient levels of detail

We introduce a representation, called a Multi-Level Progressive Mesh, for managing Levels of Detail (LODs) of a triangular mesh, allowing to store in memory an arbitrary number of LODs, with only about a 10 % increase in memory usage with respect to the highest resolution mesh. We assume that LODs were generated by a previous process, and concentrate on representing them efficiently, allowing progressive display and transmission. Our format is particularly adapted for changing LODs interactively (including smooth transitions, or “geomorphs”). We show snapshots of our implementation on a Pentium (TM) 133 Mhz PC, using VRML and Java. One aspect of this approach is to encode the LOD hierarchy using an array of representatives, one for each vertex except a few. The same array provides information to access all the LODs. Another aspect is to partition the vertices and triangles of the mesh in several levels of details (by assigning an integer level to each vertex and triangle), and to re-enumerate the vertices and triangles according to the levels. Key-words : Triangular Mesh, Levels of Detail (LODs), Progressive Transmission.