@granada
Single texture... 2048x2048. One "X" file only.
Using the modeling software I use (ac3d) I am able place the glass (after the building is complete) into the openings provided (as the last things drawn) in the model.
I can then capture just the glass as a "group", and slide it out of the building proper. Then ac3d allows me to merge the building meshes, with out the glass, and covert it into a single object. Then I slide the glass back to it's original location in the building and then save the composite as the final "x" file.
This process means a seperate "x" file containing just the glass for INSERTION into the building when in the gg editor is NOT required.
The window transparency is set using paint.net, the software I use to create the texture file (-color.dds).
I have no idea what modeling software others are using so this explanation maybe of no real value.
Windows 10 creator,64 bit| Intel i7-7700 @3.60GHZ Quad|CPU PASSMARK 10,794|Memory 16GB |NVIDIA GEFORCE GTX 1070|GPU PASSMARK 11,071