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Rotobrush matte turn into Vector (pen) Point Mattes?

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Todd Dorenfeld
Rotobrush matte turn into Vector (pen) Point Mattes?
on Mar 14, 2011 at 12:00:27 am

What I want to do is use the Matte information gathered by using the Rotobrush tool, then turn it into a points matte (with keyframes for each frame) that the pen tool creates. That way I can really meticulously refine my mattes by hand. I have the Cintiq but the rotobrush doesn't seem to care how precise that machinery can be. So I would like to use the points to get that much more precise with my mattes, on some selected frames, not all frames. Note* I am doing stop-motion matting here. So my clips are picts sequences shot generally on 2s. (meaning there are two identical frames per each frame. I am doing this 'in-camera' and not using changing my clips frame rate at all.

thank you

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Dave LaRonde
Re: Rotobrush matte turn into Vector (pen) Point Mattes?
on Mar 14, 2011 at 3:47:35 pm

There's a roundabout way of doing this. When your rotobrush work is complete, you can precomp the footage and use Autotrace. Then you can create masks and tweak them to your heart's delight.

However, in my experience, it's just as good and a whole lot faster to pull a chroma key than it is to animate a mask, especially on stop-motion footage. You have more control over exposure, depth of field, etc. from frame to frame as opposed to motion picture footage. The nature of the footage eliminates the problems of color sampling (aka color resolution) that come with motion picture footage, too.

But if the nature of the shot means you can't pull a key, I don't see why animating a mask would be necessary if you use Rotobrush in conjunction with Refine matte. I just don't get it.

Nor do I get the reason for shooting on 2s. You're simply doubling the amount of footage you deal with. It's much easier to conform the image sequence to the desired frame rate. Shooting on 2s may have been the thing to do when stop-motion was done with movie cameras, but that was decades ago. Now you can shoot RAW on a DSLR and make it any frame rate you want.

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

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