Maps that use 3D Meshes

Ran across a map today called 'Tournament Dome' by 'Degulum' which is a remake or rather import of 'Tourney Dome' from Supreme Commander 2. Evidently it actually uses a 3d mesh instead of your typical heightmap based Supreme Commander map. In order for it to actually work I had to use a mod called 'Marlo's 3d maps' also made by Degulum. Does anyone know how this works? Screenshots below:
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Could just ask them yourself @Degulum

Hello,
Im glad you stumbled across my map. This is merely a proof of concept map, the biggest issue is that units will lack range circles due to how I made this work:
The mesh is split into entity meshes, I use the map script to spawn the entities and then attach the map meshes in the center.
To get unit collision I just use the normal heightmap, but I use the hide terrain console command, so basically this is still a normal map but the terrain is hidden and visually replaced by a mesh. This is why I need the mod, which contains these meshes.

Now since the game renders thing like decals, unit range rings, building outlines etc. ontop of the heightmap, all these things also get disabled when I hide the terrain.

@degulum thanks! I loaded your map in the map editor and noticed the presence of the normal height map. I think your execution was pretty smart with hiding the actual terrain for collisions. Pretty cool!

Is it possible to make a transparent texture for the map?

@speed2

Yes transparent textures do work, Jip has done a lot of work on the shaders and Its even possible to do terrain culling, but this has the same issues as the console command, ie range rings etc. dont render, it may be possible to create an entity shader that does render range rings and decals on it, I dont know