3D relief with Sketchup and photoshop

[Francissimo]

Hello there. I've tried an alternative way to represent perspective in a map. Instead of drawing elements in photoshop to give an iso feeling (hard if you have poor drawing talents) i start from a 3D modeler, sketchup here, to build the main elements of the map. The hills and mountains were drawn using the sandbox tool of sketchup. The sandbox is really a powerfull tool to create relief, the only weakness is that you have to get a big number of polygons to have natural mountains, on that attempt i was far from pushing the app to its limits, i think it's possible to draw much more realistic mountains if you spend some time on it.
I also add buildings in sketchup, a way to be sure the perspective is ok. After that step i choose a view, export my layers in 3 jpeg in photoshop (1 for the lines, 1 for the shadows and 1 for the terrain) and starts adding effects like textures ect in photoshop.. I also add a few trees with treething, (drawing forest is so quick with that tool!) The problem is that i add all the trees at the same scale wich kills a bit the perspective, but that's more a test than a final map so i was lazy on that point
Feedbacks and critics are welcome and if cartographers have already tried this approach i would enjoy a few tips!