Hi Zepeu,
I think that the issue always seems to be Terragen is good at generating terrain and not hugely great at animation work or built-in setups for creating specific types of rivers, roads, shaders etc. A lot of this has been worked on by the community here and there are files to help, but the animation tools are still very basic. Unfortunately, animating is not particularly well integrated at this stage. If you need to animate cameras a certain way, take a patch of terrain out of TG, import it into another package and animate the camera there.
There are a few ways of getting terrain out. My favourite is to make a new camera pointing straight down and use a micro poly exporter to export an obj from a new render node. Keep render detail setting low or you can end up with HUGE filesizes. Bring that into your 3D app of choice, animate your camera, then export it as an FBX. Then you can import that into Terragen. It might come in at a different scale depending on your FBX settings. Ideally work near 0,0,0, in TG, ie the top of the planet. You can work anywhere on a planet of course, but doing it on the top is less of a headache most of the time.
Glow worms may need animating over terrain this way too perhaps.
I agree seeing motion paths would be nice sometimes.
GPU rendering is not possible with TG right now, based on someone else asking the same thing a short while back.
