This is an X Windows based program for the view dependent refinement of progressive meshes. In this program, I implemented the refinement thru edge collapses only. So I start with the original mesh and perform edge collapses so that the detail level is adjusted to the desired level. Detail level is dictated by the view frustum, surface orientation and screen space error. For example, the portions of the mesh outside the viewing frustum or the parts that look away from you are refined to a lower detail level. The refinement step also takes the screen space error into account, i.e.: distant parts are fined more, flat areas refined more whereas silhouettes are refined less. Since I performed edge collapses only, the refinement step is lightning fast. I don’t have to go through all the topology checks. Because I start from the original mesh. this also simplifies the ecol structure. So I don’t need an outrageous disk space requirements. This also enables topology comprising refinement. For example, during the refinement, unconnected parts of the mesh can merge together (of course this depends on the underlying edge decimator. I used Garland’s Simplification by Quadric Error Metrics).