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render passes with straight alpha?

Posted: Fri Jan 30, 2015 9:27 pm
by the singin' ass
hello,

somehow i can't figure out how to render with straight alpha channels. the beauty pass looks fine. but the other passes (refl, dif...) don't have straight alpha.
interesting fact: they look fine during rendering in c4ds picture viewer; but the saved exr-files don't have a straight alpha anymore..?

or, other question/solution:
does anybody have an idea how to unpremultiply the renderpasses in after effects to get nice smooth looking borders on alpha channel?

thank you so much for your help!
best, julez!

Re: render passes with straight alpha?

Posted: Fri Jan 30, 2015 11:36 pm
by aoktar
2.20 CS2? You should check saved images not picture viewer. There is problem which is related with presentation. If you change it use "alpha premultiply" in camera imager. But be aware it's not good for opacity. Please post some samples if does not help.

Re: render passes with straight alpha?

Posted: Sat Jan 31, 2015 2:50 pm
by the singin' ass
Thanks for your response!
Unfortunately, I still can't find a solution.
I guess it's easier to say what I want than what I did ;).

I have a basic scene with a HDRI-Environment, an Octane-camera and simple geometry. I want to render it using the different Renderpasses and comp them in After Effects on a new background. But I always get the dark border from the alpha-channel. My solution would be to render the passes with straight alpha (and add the alpha from an object-channel in the end). But I can't figure out, how to get the straight alpha...

Thank you for your help!

Best, Julez

Edit: I'm using latest Octane with latest C4D Plugin

Re: render passes with straight alpha?

Posted: Sat Jan 31, 2015 9:03 pm
by aoktar
can't see same error on my trys with psd's. you should post your bad scene here to test it.

Re: render passes with straight alpha?

Posted: Mon Feb 02, 2015 2:30 pm
by the singin' ass
Hm, strange. I guess I misunderstand something totally. Would be really nice if you could have a look at this scene:
It renders 4 passes. If I add them together in AE I get this black border...

Thank you!
Best, Julez