I'd love to figure this out as well - and I think it might be manually possible after the fact, if I were to import the heightmap as a layer in Paint.NET, and use that to guide the editing. You'd then need to start a new game with the updated biome.png to make it take.
I haven't paid close enough attention to this thread. This is actually very easy to do. I see that Joe posted a contour map I generate as well, but this is WAY easier than the contour map. All we need to know if the elevation is above a certain threshold, then change the biomes map accordingly.
For example, looking at the seed I'm using I can see that the most common elevations are between 34m and 39m, but it goes all the way up to 226m. The water level is fixed at 29m in alpha 20. So where exactly is the "mountain peaks"? Here's what the elevation looks like in this map (this is upside-down because that's what Unity uses):
Ideally, the mountains would be the white "dots" we see, but to find out what that is takes a bit of trial and error. I tried a few numbers and 100m looked good enough to me:
That was produced with the following command:
Code:
magick convert -size 8192x8192 -depth 16 gray:dtm.raw -flip -threshold 25600 -transparent black m.png
(the image I pasted was further transformed to reduce its size and remove the transparency)
Everything up to "-flip" is just how the elevation image, dtm.raw, must be handled. They don't have metadata so one must specify size and depth, and they are upside-down. Then -threshold splits the image in all colors below 25600 (100 times 256, since 1m = 256): everything above is white, everything below is black. Then I turn black into transparent so I can overlay that on top of the biome image later on.
As it happens, snow is white in the biomes image which is rather convenient. This is what my biomes look like:
And then I overlay the "mountains" on top of it with this command:
Code:
magick convert biomes.png m.png -composite biomes-m.png
And I get the biomes below, which I could then use instead of my current biomes:
And here are some screenshots afterwards: