The next step forwards deals solely with graphics. The terrain mesh and railway track are now rendered with procedurally generated textures, and most models with hand-painted textures. At the moment, all their shaders just output a diffuse texture sample as the fragment color.

Aside from unwrapping and painting models by hand, I had to spend a fair bit of time automating model exporting from Blender. The procedure involves unwrapping all objects onto a single UV map, then setting up new materials for each with a shader that takes one source texture for each object, and bakes all of them to a single texture atlas based on the collective UV map.