View Full Version : Lighting through a window!!

03 March 2011, 01:35 PM
I have been looking allll day for a tutorial on how to get light to pass through a window and there are millions on how to set up the lighting but none of them tell me how to get the light to actually go through the window?

What material do I use? How do I set it up? Does the entire scene have to be enclosed?

I want to animate a sunset so is there anyway of setting up MR physical sun/sky to pass through the windows??

I'm new to lighting but I really want this to look good for my uni projects if anyway can point me towards a tutorial or give me some step by step instruction I would be very grateful!


03 March 2011, 05:41 PM
yes light can go through windows. in Mental Ray you simply make the object transparent (removing the diffuse and giving you refraction+reflection). to create realistic glass simply turn on fresnel reflection and set the index of refraction to 1.33 (also the same as skin). you can then have the window cast a transparent shadow, or use caustics (there are check boxes - i'd advise sticking with the transparent shadow, caustics are a whole other can of rendertime). btdubs i'm assuming your using mia material.

one thing to think about though is a tradeoff of speed vs quality. messing with render stats to make the renderer ignore the pane of glass will speed up your rendertimes. If your going for an effect like stained glass or dust on the window and you want the light interacting, then by all means, use some glass.

-hope that helps

03 March 2011, 09:02 PM
If you're using mental ray, simply use Portal Lights.

So you create an area light, fit it to your window (outside the window glass), then link the Portal Light into the Custom Light slot, then link your physicalsky into your Portal Light. It's that simple. The Portal Light also acts as an FG concentrator, which will make your scene render MUCH faster and also look far more accurate.

If you're doing interior rendering in mental ray, you should be using Portal Lights for every window or door that would have sunlight coming through. For glass objects, make sure your normals are proper, and also that your ray-depth is up high enough to accomodate the two or four bounces you're going to need.

03 March 2011, 02:19 AM
Do you plug your physical sky to the portal lights environment?

03 March 2011, 03:04 AM
Yep, you plug it into the sky if you want it to concentrate sky FG rays. Also, this is how it gets its directional light intensity automatically from the physicalsun's directional node. This is best for indoor shots.

If you don't plug in the sky, you can use the Portal Light as a "light card". You can plug in another node or, say, an image file if you need cool lighting for product showcasing, etc. I used this technique recently in my latest personal project, posted here ( if you want to see how it worked.

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03 March 2011, 03:04 AM
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