The paper does exactly that: download a DEM height map and do shading from that. What they argue is that you can customize the amount of detail of the terrain t

The paper does exactly that: download a DEM height map and do shading from that. What they argue is that you can customize the amount of detail of the terrain to make it look hand-made (since an artist shading by hand wouldn't be able to interpret small variations and flat areas of the contour plot as well).