What are triangles indexed for?
The problem with terrain is, that my terrain would need to have a resolution of something like 100kx100k vertices, which I haven´t tried for a long time and can may be created per script, but at least MED when I last tried it was not able to handle terrains with a higher resolution than 1024x1024 or something like that.
Also, I don´t need a plane, but just some rivers to be covered. I could of course masked terrain, but that would still cause way too many vertices to be sent and processed by my graphicscard. And I am also not sure if the terrain LOD would be able to reduce the polycount as much as I would like it to.