Model Requirements
-Scale using satellite imagery as a reference (screenshots can be obtained from Google earth)
-Clean non overlapping geometry, with holes for windows, doors and other accessories
-Create materials and optionally textures for various building parts, make UVs as necessary
-Create a clean UV map that doesn’t tile (is all contained within the UV space)
-Bake all materials, solid colors, and lightmaps (with flat ambient lighting) into one single Diffuse texture with the clean UV map that you’ve created, if you made other materials using tileable textures and UVs that extend past UV space, make sure to make another clean UV map within UV space.
-Bake specular and illumination maps for windows (a map with black color for walls and white color for windows and parts that are supposed to illuminate at night).
In this case, the specular and illumination maps are the same:
-Make sure the origin of the model is at the bottom center of the model.
-Export OBJ model at 100x scale of what you already scaled it as in your 3D program (.mtl file isn’t needed), and include the textures with it separately.