My plan of assembling the desert maps is making just 512x512 sized tiles created via gensurf.
To roughen them a bit you can use the fractals. But to make a big hilly landscape you can change the height of the corners to values like 0, 64, 128,...
Making different tiles that way you can connect them correctly via the .ump file and you get a very easy and fast way of creating landscapes. (Of course you should add some models or details, but this is just about creating the landscape)
On the first picture you can see one of those single tiles. On the second one they are connected, how they get connected ingame.
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