I know WM has a node to make a normal map from a heightmap, so its pretty easy to make one, but is it worth it (or even useful) to make a heightmap for the terrain of every regular battle or settlement scene.
It probably depends upon the type of scene. Lots of mission scenes have rolling terrain and rely on rock meshes for detail. In such cases, a vista normal map would be pointless. If however, the terrain mesh is attempting to reflect complicated or rugged terrain then a normalmap should help if its resolution is high enough.
On a 8x8, 512x512 scene, for example, you would need a 4K heightmap to give one pixel of height data to each vertex. Accordingly, a 4K normalmap would be too low resolution to add extra bump detail to your terrain mesh. To gain any benefit you would need an 8K or 16K version.
I've not tried using a vista normal map without a vista diffuse and vista alebdo, but assume it can be applied without them. Loading a new 16K normal map can make your terrain disappear for a while until the editor recalculates its impact and redraws the scene. Also, unlike the heightmap, which should be a power of two texture plus 1, a normalmap needs to be power of two only. The heightmap isn't compiled as a tpac. Compilation will fail and the normalmap will be held unoptimised, if it's not a power of two (i.e 4096x4096, 8192x8192, 16384x16384 etc).
Obviously, the higher the resolution normalmap the longer the World Machine build time. For 16K textures, I've had to use paged memory as World Machine wants more than my 32Gb of RAM.
EDIT - To get any value from the increased resolution of a normal map you probably need to reset the resolution of your normal map in the terrain property_browser so it is not 'Same as terrain'.
