I had a bit more time to experiment, and it's absolutely related to the detail levels, and not the size of the planet. The planet I want to make (and shown above) is 475,000 units in radius. My detail distances array is size 8-9, I didn't experiment with much variations there yet. Detail distances calculator starts at 2,500,000. For a test, I just tried a 100,000 radius planet, with the detail levels set to size 6, same heightmap, detail distances calculator starts at 500000, and it looks ok. I expand the size of the details array to 7, and the artifacts appear again, just not as clearly. Settting the detail levels to 8 and the artifacts become very clear again. I then made a planet 5000 unit radius, distance calculator 25,000, with 8 detail levels, same heightmap, and I can see the artifacts. It seems that the size of the planet doesnt matter, but for detail levels 7 and higher the artifacts appear, the higher the detail level, the clearer the patterns become. I am just experimenting with with various parameters so far to get a nice result. I can't really say what I need yet, but I notice that my planet looks all smoothed and blurred out if I have lower detail levels. I want crisp , sharp geometry as much as possible. I've been adding in extremely high frequency noise along with the hieightmap in Hybrid mode (this extras noise is not included in the screenshot above) but I find that I need these high detail levels, maybe even higher, otherwise everything looks like soft, gently rolling hills when flying near the surface. If there's a better way to get rougher, more detailed terrain I'd be grateful to hear about it.