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rob rhodes
04-16-2007, 11:28 AM
I was wondering if there was some film motion tracking software ('A') out there that can pick up and select moving pixels that encroach on a pre defined selected are on screen. To explain more:

Imagine if I had a video camera fixed on a tripod and was filming and infil site (gap between 2 buildings that is going to have a building (3D model) inserted in the gap). At some point there will be an opportunity to capture a frame where there is nobody walking in front of the site or a car passing by. If I take this still and select and store this area in software 'A' will it be able to cut out an alpha channel or whatever so that anything passing in front of the building area (inserted 3d model) during the course of the video footage, can pass over the top of the model I.E. look like the building is actually there. I know there will be problems with reflections etc. but just working on this general principle, A. Is there software out there that can do this and B, is it affordable (sub £500)?

Hope you can understand my ramble!!

Cheers, Rob

MrBrick
04-17-2007, 03:14 AM
I think I know what you are saying there..

Why not just use After Effects and try tracking the guys and then painting an alpha map over the guys? I'm just entering the fray on after effects and theres a tons of tutorials out there. This seems like something it could do so maybe someone else can cofirm in a bit more detail.

Hugh
04-17-2007, 02:20 PM
It's called a Difference Key, and I'd imagine that most software supports it. This method definately has issues, though, in as much as an object or person moving in front of the background may have similar colours to the background at that point. This will create holes in your key....

MrBrick: You're effectively suggesting rotoing the people/objects. This is, I believe, what the original poster is trying to avoid.

rob rhodes
04-18-2007, 10:37 AM
Yes thanks Hugh, that is what I was hoping to avoid! hmm looks like there needs to be some more investigation into this.....

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