In USGS you can select PNG formats for export…
World Machine
There must be more recent options. But since Udk’s time I use the “UDK Layers Macro” as output to define the terrain layers material, and the basic output in Raw16 for my heightfield terrain.
The terrain generated by the previous function (*Height output)
Blender currently, but the Perlin Noise algorithm is looking pretty sexy.
Worldmachine for me too. But I have in the past converted some actual scans of mars and the moon in the past with good results.
and like I have used that macro before with good results.