Thank you wolfgangp! 
I’m currently very busy, but I think when I have some more time I can write some documentation about getting heightmaps (and other maps) exported from worldmachine 2 into panda3d, and rendered.
I can’t do a complete “How does worldmachine work” tutorial, that would be an overkill, but I think I can give a rough overview, and upload some sample projects (there are also some included, I think).
To give a basic overview about the workflow:
There are currently two terrain renderers, one which loads all textures at once, and one which streams textures from disk (that’s the one 'm currently working on).
Assuming you do not use terrains >= 8192x8192, you can use the renderer which loads all textures at once. If you need bigger terrains, terrains with a resolution up to 65536*65536 are supported, even if they would probably be too huge on disk, and I would not now any application which needs that amount of terrain.
The terrain requires a heightmap with 16-bit precision, you can export it in WorldMachine 2 with the “Height output”, check PNG there.
As the second map it requires a pre-computed normalmap, use a “Normal-Map Maker” with the default settings, and connect the out-slot to a “Bitmap Output”. If you select PNG there, it will be 16-bit, I used photoshop to convert it to 8-bit.
The third and last map is the texturemap, where each channel represents a texture (currently red=snow, green=gravel, blue=sand, alpha=rock). The parts on the terrain where none of the four textures is present, grass will get filled in. You can use a “Channel Combiner” for the first three materials, and connect the rock factor to the alpha-input of the “Bitmap Output”. Again you would have to convert it to 8-bit.
For the Build Resolution, I reccommend 512 for development/testing features, and 4096/8192 for production.
If you have any further questions, just ask