Ah I've just discovered what you mean. If a user creates a glass object then imports it but without ticking the door/window tick box then it appears as glass in the 3D view but light doesn't render through it; if they then take the same glass object and import but this time click the door/windows tick box it still appears the same in the 3D view but is rendered as an invisible object so light passes through the space.
Aww I got all excited again after my above test results!
This also explains why I wasn't able to add a shiny surface to one of my floors. Knowing that imported objects can be coloured or textured with an image map I wanted to make a wooded floor with a slight gloss to it (without having to make a massive imported shiny wood textured obj or lots of the same object repeated)
So within (Sweet Home 3D) I used a box (the building has two floors) for the first floor, applied a repeating wood jpg texture and was then going to overlay a thin, small (made larger in Sweet Home 3D to cover the textured box) semi shiny glass obj over the floor but kept wondering why the floor with overlaid glass obj always appeared black with reflections while the glass in a doors didn't seem to stop the light, because they aren't actually rendering the glass as glass.
Interesting!
db4tech
