Author Topic: about alpha masks for compositing  (Read 10617 times)

2017-03-27, 12:56:57

magmatik

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Hi everyone,
first of all I'd like to say that I love Corona and thanks to it I've totally let AR down in C4D (until then I didn't really try another render engine).
It's just madness with new Ryzen 1800X+ GTX1070 config !

That said, I'm facing a problem : I can't get an alpha mask on specific item whatever the tag I assign or not to it.
I always get a mask on all the items of my scene (wich is quite a problem with full frame L-shape background > the mask is fully white).
I assume that I'm probably missing something.
Please see the attached picture.

Could you please give a link that explain how it works or tell me here where is the trick?

Thank you so much in advance.

2017-03-27, 13:41:31
Reply #1

CBAS VISUAL

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Same, i dont know how to exlude an object from alpha.
The corona tag should do this but it doesnt work.

R18, a6.3, win10

2017-03-27, 14:11:22
Reply #2

magmatik

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R18, a6.3, win10 64 too

2017-03-27, 14:57:40
Reply #3

synolog

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Hi, in corona multipass, under mask, under "multiple condition mixing" select "Intersection AND". Remember to select Object GBuff ID

2017-03-27, 15:35:38
Reply #4

magmatik

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Hi thank you for the answer.
I did what you told. Still not working...
I really don't understand what's wrong.

2017-03-27, 15:53:36
Reply #5

synolog

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You need only to select object Gbuff ID

2017-03-27, 16:09:05
Reply #6

magmatik

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You're right I had forgotten this point but even by enabling this option, it doesn't work...
Really sorry for the trouble.

2017-03-27, 16:15:06
Reply #7

synolog

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Could you send me your file?

2017-03-27, 17:42:50
Reply #8

CBAS VISUAL

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Create a Corona tag on the object u dont want the alpha, uncheck visible in mask
Multipass, add a mask pass, Multiple conditions mixing -> Instersection(AND)

That's all.

2017-03-28, 12:16:12
Reply #9

magmatik

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It still doesn't work as it should, even with your last advice... :S
Why isn't it as simple as in the basic C4D ?

synolog, have you had an eye on the file I sent you ?

2017-03-28, 13:06:13
Reply #10

synolog

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Yes, i've sent you a reply in pm. You forgot to activate the multipass.

2017-03-28, 19:17:40
Reply #11

magmatik

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@synolog: thank you for your answer

I'm quite sure multi-pass was activated during my tests.
I'm keeping trying to get proper alpha masks and I still can't get them.
I won't bother everyone more with my problem.

Could just someone (synolog ?) share a file with a proper multipass setup (with a basic scene like cube + sphere -> alpha only on cube or sphere) ?

Thanks in advance.

2017-03-28, 21:55:58
Reply #12

synolog

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3 cubes, 3 masks

2017-03-29, 10:26:47
Reply #13

magmatik

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Hi synolog, thank you very much.
I get alpha masks as they should be with your file.
Will keep it preciously as an example of what to do.

2017-04-03, 11:52:56
Reply #14

basor

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Sorry for bringing up this topic again, but is it somehow possible to get the material IDs as direct alpha channels for post production in photoshop or do I have to save the masks individually and add the selection as a new alpha?
Also, when I select to save all the render channels at once it never saves all the masks, just one single one. Am I doing something wrong here or is this already known?

Thank you guys!