CGTalk - Quicker Renders with GI? What?

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Nerfbat

11-04-2005, 11:24 PM

So I was sort of optimizing part of a project I'm working on, trying to get the render times down to something I can deal with. After a few hours of tweaking, mainly on my lights, I get the render time down to about 1 min 30 sec per frame, from like 8 minutes, with no noticable loss in quality. Just out of curiosity, I turned off all the global illumination in the scene, to see how much that would cut it down...

It didn't. Turning global illumination off actually made the renders slower. It took about twice as long to render the same exact frame with GI off. Nothing else changed. Not that I'm complaining, but.. how is that possible?

Screenshots here if you're interested:
http://portfolio.iu.edu/rbilbrey/temp/idontgetit1.jpg
http://portfolio.iu.edu/rbilbrey/temp/idontgetit2.jpg

Jozvex

11-05-2005, 01:03 AM

Interesting!

Two semi-explanations I can think of are:

1. Are you also using Final Gather? Photons can speed up FG by providing a good starting point. Also because the scene is slightly darker without the GI, the FG might just have more of a hard time.

2. Maybe because the scene is darker and more contrasted without GI, the adaptive sampling chooses to go to a higher sampling level?

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