Ah yes - I forgot to add that the glass wall is set to be reflective in rendering q3/q4 (using g sweethome3d_window_mirror in the .obj file - like a mirror - see the rest of the thread).

This example - glass_walls_reflection_and_not.sh3d - shows the same window with reflection (marked with a danger sign) and without reflection.

I posted the two other windows used in the example too in case the lab does not want reflective glass walls. As for the general transparency, you could change the d value in the .mtl file. But I guess it is the rendering you were after...

ok