I tried volumetric ligting, but it always buggs me, because it is so slow. So i used some different effects to fake that light spreading. Here is a screen from the render setup: prntscr.com/bxtms9 there is 1 sunlamp for the sharp light coming in, 2 area lamps for lighting it smoothly, the ceiling glows purplish for even more smooth light, there are walls, that ware visible to the scene, but invisible to the camera and some lamps over the desks (emittive material). Here is a clayrender of everything: prntscr.com/bxto85 I also went over the window area with a very smooth yellowish brush in gimp, to enhance the glowing effect. All that helped me getting nic, smooth lighting, without the need for real volume scatter.The only thing that uses subdiv are the coats and the plants. everythign elese either uses bevel or just has smoothed vertices and a high polycount.