Re:Multigen only (Score 1)

There IS an alternative! Check out Geo at www.carbongraphics.com. Geo is a real-time modeling & animation system geared to the needs of the vis-sim community (as such, it goes head to head with MPI). It comes with an extensive plugin SDK, data-driven behavior engine, industry-standard file format support (e.g. OpenFlight) and its own extensable real-time file format. Its also very cost effective, compare to MG.