4 Replies Latest reply on Feb 29, 2008 5:05 AM by Jonas Hummelstrand

How to use multiple alpha channels

Navarro Parker Feb 27, 2008 1:40 PM

Hi there. I'm using Cinema4D for some 3D animation. I'm using an object buffer compositing tag to isolate certain elements in my scene. (C4D can create an alpha channel for each object). This is then rendered out as a multi-layered PSD sequence. However C4D puts the extra channel info (z-depth, object ID, etc) into alpha channels. But AFAIK, AE only reads the first alpha channel.

Is there a way to read extra alpha channels?

1. Re: How to use multiple alpha channels

Mylenium Feb 28, 2008 2:25 AM (in response to Navarro Parker)

>Is there a way to read extra alpha channels?

Only via Photoshop batch processing. If you can afford it, simply re-render with the multilayer file option unchecked. Other than that there is no way for AE to see additional custom channels in PSD files.

Mylenium
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2. Re: How to use multiple alpha channels

(Steve_Patterson) Feb 28, 2008 10:20 AM (in response to Navarro Parker)

You can render out to a different format. Try RLA/RPF. They can include alpha, z-depth, and objectID, I believe.
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3. Re: How to use multiple alpha channels

bogiesan-gyyClL Feb 28, 2008 1:09 PM (in response to Navarro Parker)

This topic came up about two years ago, you might try searching the forum.
IIRC, the conversation was enlightening for several of us old timers who had never even heard of multiple alphas.

Closest I've ever gotten was using the four separate color channels to hold unrelated grayscale movies. Each was used to drive a different 3d parameter of Card Dance.

bogiesan
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4. Re: How to use multiple alpha channels

Jonas Hummelstrand Feb 29, 2008 5:05 AM (in response to Navarro Parker)

Try the "ID Matte" effect. Works for RLA/RPF rendered from 3ds max.

- Jonas Hummelstrand
http://generalspecialist.com/
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