light pass composition photoshop

[fraggle]

To all Vray user,
Can you please share your knowledge regarding light pass composition.
I've done an interior rendering with different pass for the light (exterior light, sun, ceiling, photometric wall mount...), but I don't understand the physic behind it to recompose the final image in photoshop.
I found some interesting tutorial regarding GI, Shadow, depht of field pass, but nothing regarding composition of diffrent light.
I used the Screen layer function in photoshop, but I don't really know what I'm doing.

Thanks for your help.

[rivoli]

well, if you're after something like what maxwell and fryrende do with lights in post, you should be rendering one image per light (or group of lights), as I guess you did, save to a hdr format, and then add all of them together. as you work linearly, the correct operation/blending mode, is add not screen.

[fraggle]

Yes, that's what I'm looking for, a flexible solution to fine tune the light live.
Do you mean Linear dodge (add)?

Thanks

[rivoli]

yep, that's the one. still can't understand why they can't just call it add, as for any other app..

[instinct]

In nuke it's called plus [/nitpick]
At leat it's an equivalent name

[rivoli]

eh, yes it's the idea that counts
linear dodge sounds more like the opposite, either that or it's totally meaningless..

[fraggle]

Ok, what about Autodesk Composite? You, guys, seems to use Nuke/fusion... and I do not own license but I do have composite. Any idea how to do it in composite?

[MoonDoggie]

Yes, mix them together with a Blend & Comp node set to ADD and you'll get the same result in Composite.

[glorybound]

Holy cow! I didn't know we can do this?

[MoonDoggie]

I'm not composite expert, but I did watch the tutorial videos :P

[glorybound]

and I suppose we can animate lights coming on in After effects? Any good tutorials on that?

[fraggle]

I'm not composite expert, but I did watch the tutorial videos :P

thanks, I will try to see if it's more easy to handle than photoshop when playing with 20 layers.

What tutorial are you refering to?

[MoonDoggie]

It's hard to find tutorial videos online of Autodesk (newly renamed Composite). Search for "Toxik tutorial". Here's one.

http://www.youtube.com/watch?v=PZNFt_GHeIo

Hope this helps. I don't love Composite by any means. Nuke is much better, however, Composite is free, so I've taken to trying it out.

If you have any Composite (Toxik) questions, let me know.

[glorybound]

I have After Effects. Is Nuke better that AE, or is it apples-to-apples.

[MoonDoggie]

Nuke is the best compositing software in the world.

After Effects does _alright_ compositing (it's easy enough to get similar results, and very hard to get exact results).

Nuke costs $5000 USD. AE is considerably cheaper.

If you're doing compositing, use Nuke, or Toxik (renamed Composite, now ships with MAX), if you're doing motion graphics or just color correcting some footage and adding text, use AE.

Just my 0.02