Both are pretty easy in terms of getting data out of Terragen. There are challenges with each depending on the capabilities of your destination program though. An exported Spherical Camera render can be used immediately by most 3D software as an environment map with Spherical projection, but many game engines want a "skybox", i.e. a 6-sided box with images (or image sections) mapped to each side, and in this case you'd need something that could convert a spherical camera output to skybox format, or to manually render out the 6 faces yourself (6 different camera views at 90 degrees to each other). Some game engines natively support spherically mapped images anyway.
Geometry exports in OBJ or FBX so as long as your destination software supports one of those, it can load the geometry. The main challenge comes into play due to geometry density/object/file size. But this is just a fundamental reality of the level of geometry Terragen generates to create the detail that it does and is one reason why we generally recommend rendering high detail terrain in Terragen rather than trying to export it and render elsewhere. Exported terrain is generally better used as a shadow-receiving object, for occlusion, camera path creation/reference, etc.
- Oshyan