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Activity › Forums › Adobe After Effects Expressions › 3D camera position to influence footage speed

  • 3D camera position to influence footage speed

    Posted by Samuel Gilmore on November 11, 2015 at 6:24 pm

    Hey there, I’m really stuck on how to achieve a perfect forward track in After Effects.

    I’ve encountered this a few times, I’ve got some footage thats been filmed with a dolly and it’s come out fine but it’s not moving forwards at a perfectly consistent speed because its been pushed by hand.

    How would one use the camera’s 3D position to distort the time of the clip so it brings up the slowest points in the track to the fastest moments thusly keeping the forward movement equal throughout? I’m guessing I need to plug in the Z position to Twixtor’s percentage speed or frame number but I’m really lost.

    Any ideas? Thanks so much!

    Kalleheikki Kannisto replied 10 years, 10 months ago 2 Members · 3 Replies
  • 3 Replies
  • Kalleheikki Kannisto

    November 12, 2015 at 7:10 am

    I would think you’d have to go about it a bit differently. You’d want to compare the 3D position of the camera to an ideal (linear) interpolation between its beginning and end positions (at beginning and end keyframes) and use this value for time remapping to remove the difference. Pixel Motion frame blending could work for creating the in-between frames.

    That’s my first theory.

  • Samuel Gilmore

    November 16, 2015 at 10:11 am

    Thanks Kalle. That line of logic surprisingly makes a lot of sense to me but as a man with a pitiful knowledge for expressions I’m stumped at where to start implementing this. Could there any recommendations of anyhow to get around this problem I’m not thinking at? Looks like there was a similar question raised on these forums that didn’t get anywhere.

    I’ve seen it fixed enough times I assumed there’s some plugin for it but maybe this is one for the graph editor.

  • Kalleheikki Kannisto

    November 16, 2015 at 1:43 pm

    Without test footage I wouldn’t know if it the solution works.

    Maybe it is too complicated a solution for the problem. If the slowing down is relatively steady, it should be pretty easy to time remap the end of the footage to look about the same speed as the rest. I’d give that a try first.

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