Take a simple cube-shaped, flat-roofed office building from the town. Forget the dead version for a minute. When you export the shape to AC3D, and open the file in Notepad, the texture bmp file is in there. Open the texture coordinate editor feature, and you see where the faces of the building are mapped onto the texture bmp.
But what tells the notepad file to apply the bmp texture to the different faces of the model. I can see it in the texture coordinate editor, and I totally get that I can do this in AC3D and blender or GiMP relatively easy. But where does the file get the information to apply the portion of the texture bmp to the face of a building? Where is the line of the file that provides the model this info? The AC3D file (in Notepad) is just a basic text file, but I can't decipher where this step is accomplished.
Reason I ask is that while AC3D is a pretty simple program, their documentation is horrible. So for anything other than a simple building, it's really hard to figure out how to do it. The consensus on the interweb is to make the model in AC3D, but use Blender to apply the textures because it's a lot more robust and documented. Then re-import it back into AC3D. If there was a way to simply manipsulate the AC3D text file to apply a texture, I would love to know how.