This technique helps to save time spent on modeling
and is suitable for models which do not have too much detail.
1. Create
a multi-subobject material which material ID 1 = wall and material ID
2 = window. You can use an opacity map or blend material for this material.

2. Draw a box following the window size and convert it to editable poly
and assign a material ID on each polygon.

3. UVWmap and assign the material on this box
4.
Create a wall and assign material ID to be 1 which is white wall and
assign the same material to it.
5. Back to the window box again, edit and copy the polygon as element
and it is ready to boolean
6. Boolean and you will see the window material stamp on
the wall with the correct UVW coordinates.
