Invisible light source through glass

Hey guys,

I want to animate an indoor scene with light mainly coming from outside (the window). I already figured out that the best way to get fast and clean renders is to make the window itself the light source. With the window closed at all times this wouldn’t be a problem, but I want to open it at some point in my animation.

I created another light source right behind the window glass and made the camera rays transparent. This works perfectly fine for the lightsource itself, but the window’s glass still reflects as well as refracts the emission shading of the light source.

How can I get the glass to ignore the light source? I already tried various light path combinations for both the emitter and the window glass.

Some renders/screens to visualize my problem:

Window closed (emitter visible through glass)

Window opened (emitter not visible to camera, but reflections in glass still visible)

(Very simple) nodes of my materials

Thanks in advance!

I still have no solution for this… :frowning: Is there anyone with an idea?
I tried to work-around with a transparent/glossy mix instead of glass for the window and made the emitter transparent for Glossy Rays.
This way, the light source is not visible - but the glass looks kinda weird and (because of the missing glossy reflections) the amount of light entering when the window is open in comparison to when it’s closed seems very unnatrual.

Here’s the difference:

I really would love to keep the glass shader.

Hey, if you share your .blend, I’ll take a quick look :slight_smile:

you will have to make the light transparent to singular light rays and use a sharp glossy shader on the window. You might have to use two area lights - one visible but of very low intensity to provide the reflections, and one invisible for th lighting. Meshlights won’t work because they will cover each other up.

Thanks, singular rays kinda did the trick (there’s not much difference to my second attempt, but it looks believable). I think the whole setup interfered with my material for the ceiling, which is transparent for every ray other than camera, to let environmental light in and reduce unnecessary bounces. The window in my last picture should reflect a peace of the ceiling, instead it shows a gray bar - the rays disappear into nothing. I fixed that and now it looks pretty nice.

Here’s the (old) .blend with the glass. Maybe there’s an easier way, which lets me keep the glass. :smiley: