View Full Version : portal lights and GI in maya 2009

10 October 2009, 05:49 AM
I have a test scene with mr sun/sky and area light used as portal at the window. Pretty standard setup. From what i understand there are 2 approaches to using portals - one is using FG only and bounces and the other using GI with FG and photons. I wanted to compare these 2 methods. With all things equal, the GI was much darker than the FG with mult bounces, which is contrary to what I thought and the examples I have seen in maya/mr examples in maya help. Below is the FG shot with 3 bounces...

Here is the both GI and FG on

Just to note
- i have portal light node in both light and photon shader slots under MR tab of area light.
- emit photons is turned on in area light with 100K total photons, intensity left to default which I think is supposed to be now controlled by sun/sky
- physical sky node is in the custom env slot of portal light
- use light shape and visible are on.
- GI is on in MR and using defaults.

I had read on post by Mr Zap that u dont need to mess around with photons at all in this setup, just enable them and copy the portal node in the photon shader of light and thats it.

Why is the GI so much darker?

10 October 2009, 06:20 AM
I would definitely play with the photon exponent and intensity settings. Most of the time the dafault intensity of the photon is too low for me.

10 October 2009, 08:53 AM
Did you turn on/off "Precompute Photon lookup" in your Final Gather options? I think this would make a difference for your second, GI scene.

10 October 2009, 09:02 AM
I will have to check - if its on by default then its on since i didnt touch that setting.
Someone pointed out that scene scale starts to be a factor once photons come in to play....My scene is a bit off in that regard and might have something to do with it : /

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10 October 2009, 09:02 AM
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