A large part of TG2's fundamental value lies in its renderer. The Terragen rendering system has been explicitly designed to do things that few - if any - other rendering systems can do. Replacing it with another system simply doesn't make any sense. You would not get the same level of results from a Terragen 2 scene rendered in Mental Ray or indeed any other renderer, even assuming such integration would be possible.
It would make more sense instead to allow TG2 to render elements of the scene that other programs struggle with and at which TG2 excels (terrain, atmospherics, lighting, instancing) and then integrate that tightly with the rendering capabilities of another system such as Mental Ray with stronger general-purpose capabilities. This is how most other such special-use rendering systems like Terragen work, either through advanced automated compositing systems or direct rendering data exchange. This is a possibility we will be investigating in the future.
- Oshyan