Thanks Kacey

Sketchup is very user friendly, but I can imagine it would be fairly trying without a mouse or a pen to control it properly. Especially the push pull tool!

Vue is tricky, until you get used to doing everything by editing the function nodes, and also become familiar with all the different kinds of node and what they do - both for the terrains and the materials. The terrain you like is created by importing a very simple height map into a terrain function and applying plenty of 'river valley' erosion to it - a procedural terrain modified by painting. (Maybe that's why I'm getting artefacts)

I was thinking of using the Vue terrain for the background to a GIMP map, but the shadows would be tricky, since they would be underneath everything, and although you can render the scene without any shadows by modifying the material so that it doesn't allow shadows to fall on it, there doesn't seem to be an easy way to render nothing but the shadows to add as a separate layer in GIMP. That's when I decided that if I was going to use 3D modelling to create the shadows, I'd have to go the whole hog and do everything as a 3D model from scratch - terrain, buildings and the majority of the texturing as well.

Once I've built the model in Sketchup, I'll probably still need to touch it up in GIMP. But at least I will have a complete 3D model I can not only map, but take a range of perspective scenes from as illustrations