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How can I reverse and calculate a position of a null object?

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Brian Berneker
How can I reverse and calculate a position of a null object?
on Dec 7, 2009 at 4:15:44 am

I have a motion track with three trackers (objects get obscured or move off the screen, so three trackers are needed)
I've applies the X and Y to three chained nulls respectively, and the third null follows the scene perfectly.

I would like to adjust the anchor position of the original video by the position of the third null, but don't know what value to pick-whip. Even though the object itself follows position via parently, there is only variable position data where the track itself was applied. Otherwise pick-whipping the null position does nothing, since technically it doesn't move.

What I really want is to know how to use my existing multiple track points to stabilize the shot without losing position between trackers. I put a lot of time into manually fine tuning my motion trackers, so I'd like to reuse them if possible rather than re-do all that work. Perhaps there's an expression to read the null's parented position and apply that somehow?

I tried re-using my track points applying a stabilize instead, but wherever the stabilize goes from one tracker to the next, the whole frame jumps to a new position and then remains stable from there.

Any help would be appreciated!!



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alex dinnin
Re: How can I reverse and calculate a position of a null object?
on Dec 7, 2009 at 10:54:55 am

Or you could download a really great script from
http://aescripts.com/trackerviz/

It's a bit fiddly.. but would really help you !!!

make sure you watch the vid as well !!!

Alex



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