general adives on 3D rendering

[Redrobes]

Your question is a bit vague. For the 3D model of a forest, what exactly do you mean ? Is that 3D objects of trees with branches or the overall canopy ? Or do you just want to raise up that general area.

My advice is to check out Lidar information. Those are data sets that contain a grid of heights for landscapes. You can import these data sets into some applications that can render the view in 3D but not as a model - just as a height mapped surface. You would need to extract the forested areas of it but I would say that in general forested areas in Lidar are normally just bumpy bits.

If you want to render a drawing in 3D then either you build it as a 3D model or again, create a height mapped surface. What you can do is steal bits of real world height maps from different terrain types and blend them into your map based on matching up the types to give you a height map of your map based on real world height map textures. Quite complicated.

Search this site for Lidar and also NASA has a lot of them for free. The US geological admin NOAA has some too. But I think somewhere around is a list of sources of lidar data. The UK has most of it done now and open for download and I read only yesterday that there will be a new open global map of lidar data based on the atlas satellite. So that will be pretty cool.

My blog here (link on the left) details some other methods based on photogrammetry as well but whether thats applicable I am not sure.