I’ve been wanting to create a scene in Unity based on real Martian terrain and recently chose Victoria Crater as my target. I’ve taken two NASA images, a false color image and a black and white image as my starting point. These two images below:
The B+W image is an ideal starting point for a greyscale heightmap, but it has some critical flaws. Since a heightmap uses the greyscale level for determining height on a body, the shadows in the upper left make that section of the crater significantly deeper, the lighter areas on the bottom right roughly the same height as the surrounding plane, and the white shining bits along the edge significantly higher than anything else. That makes for a very poor topographical map.
So, cutting sections into various layers allowed for some gross manipulation of the overall scaling of colors using histograms. The first heightmap looks like this:
This is a more accurate representation by far, though still not as good as it could be. The feathered texture on the lower right quadrant of the crater doesn’t appear in the rest of the crater, despite very definitely being there in the source images. There’s also a bit of noise around the rim that really should be resolved, though it was worth importing into Unity as a trial. The result is:
I’m pretty happy with it for an initial attempt. It’ll need some fleshing out on the heightmap side. GIMP is a great tool, but it’s no Photoshop and some of the finer features in PS would definitely make this easier. That said, it’s almost certainly a workable option. Maybe a future project will be training an ML brain to take astronomic images and creating topographic heightmaps from them. I’d need better sources to start with, though. For now, I’ll need another few rounds of handmade maps.