ICU external serface detector

Maybe the only solution is a true VIS precalculation - which is real tricky. I would suggest to make two versions of the mesh, one seen from outside, an other one from inside. You could use an automated process to determine what parts are visible from inside and outside (the original VIS calcualted Visibility of each part for each possible player position), so you would need to cicle te camera around the house and detect all visible Parts (eg. using the ICU Method). From inside the house you would infact need to use some kind of custerbased VIS data, or, this would be easier, simply make the windows non-transparent, so you could simply invert the VIS list...