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View Full Version : Q's about a lighting technique I read about...

raimZ
01-05-2009, 08:25 PM
Hi guys,

I'm pretty new to lighting and have been the primary lighter at work for the past 4 months or so. I never paid much attention to it while studying, but after learning some techniques and ideas and getting good results in practice...I really enjoy the whole process of it. I have to give props to Jeremy Birn and his amazing book for demystifying and removing the fear I had about lighting.

http://mag.awn.com/index.php?article_no=3038

Ok so I JUST found this article. I'm sure alot of you have read it. They talk about having separate beauty passes for each light. Has anybody used this method? I can sort of understand how helpful this can be and the control it allows the lighter because of the quick feedback loop. Can anybody shed some light on this technique? Like, maybe, how intense the lights should be? or do they used the separate light passes on top of the original beauty pass? or...i'm not even sure what else to ask. I've got too many questions but alot of it i've got some leads to answer from other threads, I haven't found anything about this yet though.

I would love hear everybody's thoughts and ideas on possibly how you'd use this technique.
Rens
01-05-2009, 10:57 PM
Like, maybe, how intense the lights should be? or do they used the separate light passes on top of the original beauty pass?
Well from what I can tell from the article the renderer stores the lighting information for each light separately as well so in compositing you have the complete beauty pass plus all the separate light passes. Which doesn't seem so different from rendering out each light separately, but with the added bonus that it's all in one neat package and that it will likely render much faster.

As for how intense they should be... depends on what format you're rendering to. Guideline would be to render very close to how the final will (might) look, without letting areas burn out (overbright larger than 1 values which you can't scale down in compositing). Of course with formats such as HDR or EXR you won't have to worry about burned out highlights as much as you can usually scale those areas down later on.

Still, I didn't work on the movie so I can't be sure as to what they used there.
Seraph135
01-06-2009, 05:29 PM
...or do they used the separate light passes on top of the original beauty pass?

That depends on what information is in each of those separate light passes. If its lighting & textures in each pass then you could only add lighting on top of the beauty pass. If its just the lighting alone without textures then you could add or subtract from the beauty pass (if your working in float). I would probably just re-build the beauty from all the separate lighting passes and not try to add or subtract from the beauty.

When you go to composite these you'll want to use "add" for the blend mode.

Tim J
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