Basic lighting problems

Hello everybody. Here is my scene: http://www.pasteall.org/blend/27415 . I have a sun pointing through a window. The only problem is that the sun doesn’t shine through the window. There is literally no light coming through the window. It has a glass shader and I disabled caustics. What is the problem here? FYI: The window I am having problems with is called Window.002. Thanks!

All objects are treated as opaque by Cycles by default. It’s a bad idea to use glass for thin objects like windows anyway. Mix a glossy shader with a transparent shader using a Fresnel or facing value as the mix factor with a Layer Weight node.

I set a glass shader to the windows. Why would cycles treat them as opaque? And secondly, you can obviously see a little bit of the light coming in from the smaller window next to the large one. Why is that?

All objects are opaque. It’s just the way that shadows are calculated in ray/path tracers. Real glass casts shadows, too. Technically, ANY light that gets through a glass window is a caustic. Cycles is the same way. No light is getting through your windows because you’re telling the renderer not to let any light through when you turn off caustics. You’re disabling any light paths that have been refracted from reaching their target.

I disabled caustics to get rid of fireflies. But that is exactly what Andrew Price did in his How To Create A Lounge Room tutorial. BUT then I remembered that he did something to make the glass completely transparent to the sun lamp but not to the camera. I know how to do that. But it still seems a bit odd that almost no light passes through glass in cycles. Is Luxrender the only renderer that calculates realistic caustics? Anyway, thanks for you help guys!

@lkariShinji: I set the HDR strength to 0 just to see what the sun lamp was actually doing. And I had the clamp set to .98 because of fireflies.

Light path nodes. Those have to be used to get glass to behave right in Cycles. You’d think it’d be really simple and straight-forward to use glass, but once lights are involved it’s not. Seems Cycles glass has crazy absorbtion properties. I ran into the same kind of thing but posted about it in the materials section rather than lighting section because to my thinking it’s the material settings affecting the light rather than the other way around.

http://www.blenderartists.org/forum/showthread.php?330152-Cycles-Street-lamp-glass-problem

Still trying to work out a “best” solution (made some crazy leaps in getting better results after digging into light path nodes and trying some oddball things) and looking to see if anyone can come up with anything better.

Might also have to make a quickie vid, if I can find a solution that is good enough. This is going to be a common problem that breaks expectations. (At least until the glass shader itself gets revised.)