In  view-dependent PMs are applied to the rendering of very large terrain models. Memory usage is minimized through the use of output-sensitive data structures. Moreover, the PM representation is stored in a way that it doesn't need to be kept entirely in main memory.
Geomorphing2 between two static meshes was already possible in [5,6]. Now a scheme is presented for real-time applications. While the mesh connectivity is modified immediately when a vertex split becomes necessary, the associated geometric changes are distributed over several frames. This technique is simple to use for the (very likely) case of forward movement of the viewer. However, it has some drawbacks, especially when the viewer moves backwards. In section 4.2 an alternative approach is presented.
HOPPE also describes a procedure that alleviates memory problemes during preprocessing. The mesh is recursively split into smaller blocks which are then simplified independently up to a certain error threshold. After that the individual blocks are stitched together, and simplification is continued with the new larger blocks. This strategy enables preprocessing of huge models even on workstations with moderate main memory sizes.