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render lights only with alpha channel and post processing

Posted: Sun Mar 29, 2015 11:53 am
by Philipp1980
Hey everyone,

I have the following problem:

I made a rendering, where some of my ceiling light spots weren't strong enough to be affected by the post processing glare effect. So I tried to render the spots only (with alpha channel) and applied the post processing effect to combine the image with my original rendering in photoshop. But when saving the image as png the post processing effects are lost (you can see them in the attached jpg image).

Is there a way to render and save the lights only with alpha channel while keeping the post processing effect?

And if there is no such way, does anyone know a way to create a similar effect in photoshop (good plugin maybe)? The standard filters aren't that good I think.

Best regards to everyone :)

Re: render lights only with alpha channel and post processing

Posted: Sun Mar 29, 2015 7:39 pm
by stratified
Hi,

You can render the post effect separately with the render passes. The only thing you have to do is enable the post processing render pass. I created my example in the standalone but you can do the same thing with the Max plugin. You can combine both passes with the add operation in ps.
Beauty pass without post-effects (this pass has alpha enabled).
Beauty pass without post-effects (this pass has alpha enabled).
Post-effects only.
Post-effects only.
I hope this helps.

cheers,
Thomas

Re: render lights only with alpha channel and post processing

Posted: Mon Mar 30, 2015 2:32 am
by caffe3
A photoshop plugin that can do all that (not sure how well compared to Octane, but it should be more than decent) plus way more:
http://software.tiffen.com/products/dfx ... to-plug-in

Re: render lights only with alpha channel and post processing

Posted: Sun Apr 05, 2015 2:19 pm
by Philipp1980
Hey guys,

thank you both for your answers! Sorry for the delay of my answer, I had a lot of trouble to do here with that order :roll:

I will try your solution right away :)

Re: render lights only with alpha channel and post processing

Posted: Mon Apr 06, 2015 12:49 am
by huey_yeng
IF you need a precise selection of the light sources as a separate pass, the Emitters pass from the Render Elements is handy too as it only render any object that cast light in the scene.

I use it a lot when I composite in Nuke as it allows me to track in a lens flare with the Emitters pass and comp it over the beauty pass.