Hey QED42, sorry I didn't see your post here until now. The process isn't really any special and is kind of an amalgamation of techniques I've seen on here. Basically I start in Gimp by making a few layers of high frequency grayscale noise; for each layer, I set the color levels to be between certain elevations (e.g. 0 - 150 m, 800 - 1000 m, 3700 - 4000 m, etc) and then give each one a layer mask. From there I can paint on the topography I want at each elevation by erasing the mask (using a variety of brushes I've collected), so it's basically a lot of time spent zoomed way in trying to paint features that make some amount of sense. Once I'm happy with how the large and medium scale things look, I read the heighmap into Wilbur for a little erosion and incise flow before sending it back to Gimp for the final color gradient.

Here's the latest piece I'm ~ done with for now.

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