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Comp with Alpha & 3Ds Max animation

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Mark Williams
Comp with Alpha & 3Ds Max animation
on Mar 21, 2010 at 11:13:57 pm

Hi, I'm working on my first comp which takes live action footage and 3Ds Max character information.

I've encoded the video from Max with Alpha information and brought that into After Effects and I can't get a transparent background, just the black - how do I get rid of that black so I can get on with sorting out the shadows and blending?

thanks.


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Kevin Camp
Re: Comp with Alpha & 3Ds Max animation
on Mar 22, 2010 at 1:02:10 am

ae would normally read the alpha channel if it sees one, but you can select the footage in the project window and choose file>interpret footage>main. at the top are the options for how ae will interpret footage with an alpha channel. it it is set to 'none', set that to the appropriate setting.

if you don't have options for the alpha channel, then ae does not see one. you may have rendered with alpha off, or you may have rendered to a codec/format that does not support alpha.... in either case you will want to either render again with an alpha channel, or render just the alpha and bring that into ae. then you can use the alpha as a track matte, or use the set matte effect to apply the alpha to the fill render.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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Mark Williams
Re: Comp with Alpha & 3Ds Max animation
on Mar 22, 2010 at 1:13:25 am

Thanks Kevin.

I should of said (with this being new I didn't think) - I've tried each of the options for the alpha and still I just get the black background - Straight unmatted, Premultiplied and inverted alpha

The only one that seemed to have an effect was inverting the alpha which as expected made my character invisible. And yes, at the point in which I'm expecting there to be something in the background behind my character I do have another layer turned on.


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Dave LaRonde
Re: Comp with Alpha & 3Ds Max animation
on Mar 22, 2010 at 5:49:23 pm

AE is VERY good at reading alpha channel information as long as the information has been recorded properly. Is there a possibility you overlooked something when you created your files?

I'd recommend that you double-check what you did in 3DSMax.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Mark Williams
Re: Comp with Alpha & 3Ds Max animation
on Mar 22, 2010 at 9:52:22 pm

thanks dave I thought that might be the case because Max renders out two files, the 2nd being _Alpha
I have added that and tried to use the track matte option between the various layers but again all that I seem to be able to do is get the inverted luma to work. Which is giving a kind of black ghost so its almost there, but I don't really understand whats stopping the alpha or inverted alpha options from displaying anything.


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Dave LaRonde
Re: Comp with Alpha & 3Ds Max animation
on Mar 22, 2010 at 10:17:50 pm

The way a Matte/Fill file combination is supposed to work, the fill contains all the picture information you want to see. Its edges can look downright gruesome, it doesn't matter.

The Matte file is high-contrast B&W image. The white parts indicate opacity, and the black parts indicate transparency. You see shades of gray only in areas of partial transparency... like at the edges, where you expect it to look smooth.

Is that what you're seeing? If not, I'd say it's back to the 3DSMax file-creation drawing board. It took our 3D animator a couple of shots before he got the transparency right in Maya. Apparently, these 3D apps aren't really helpful when it actually comes to rendering stuff out.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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