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Very Difficult track help PLEASE
Im trying to track this shot that was shot with a jib and replace the sky and sun cause its not very nice. I have tried everything to get an accurate track but its always inaccurate. The problem is that I can track the sand on the ground but since the perspective is different from the horizen and sky I cant put a sky or sun on there. I tried 3D tracking with pftrack but I didnt get a good track with that either. Does anyone have any suggestions to track the sky so I can replace it and put a lens flare for the sun.
One more question, how do I track offscreen objects that are moving offscreen or changing, is there an offset like in shake for after effects?
Here is the Movie so you guys can take a look.
https://www.papalico.com/beachtrack.mov
Thanks,
Gev -
5 Replies
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That looks like a tough nut to…track. There’s nothing to latch onto that stays on screen the whole time.
Have you tried doing it frame by frame? Shouldn’t take more than a couple hours. Maybe forget changing the sky and just animate a lens flair over the sun frame by frame. That way would be more forgiving if you’re a few pixels out every now and again.
Bendex.
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You can’t track off-screen objects, not even in Shake or Fusion. What those programs do is some kind of smart extrapolation based on the already tracked frames, nothing more. With a smooth movement this indeed can give the illusion of being a perfect track. As for your problem: The most efficient way would be geometry based manual tracking in a 3D program. Create a few planes/ cubes for the shore and the ocean, add a sphere as the sun and then try to move your camera accordingly and create a few keyframes. With some luck, this could be exported as keyframes for AE (e.g. from Cinema4D). Everything elase quite likely won’t work because there isn’t enough parallax in your shot.
Mylenium
[Pour Myl
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As far as “kill your darlings”:
granted that the sun and sky don’t look good, what’s there left in this shot ?
The sea and sand don’t look that compelling either, nor is the camera-movement grandiose.
Could you do without this shot, or replace it with a fixed shot: that would be of course a piece of cake to do a sky-repl on.
Is this view of the sea important in your continuity or could you just insert any library shot of the sea in there.It’s difficult to tell from the compressed movie, but is there enough information there to do two color-corrections: one for the waves, and one for the sky, it would be fairly easy to mask out the sky and just enhance it a bit. You won’t get any extra clouds though, but the result could be a lot better than a shaky skyreplacement.
Good luck !
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You Could go the really wacky route and stabilze the end part of the jib and slice up the video into 2 chunks (sky and ground). Clean the flare out of the ground layer and duplicate several layers of it, spacing them out and cloning over the edges. Use AE to simulate a similar camera pan using the the precomped ground layer, futzing things around as necessary. Once your camera move is done, you can replace the sky with whatever you want since you now control the camera motion.
It involves quite a bit of elbow grease, but less than it would take to rotoscope that whole mess.
-Rob
Motion Graphics Animation
Professional & Freelance
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in looking at this example I’d stabilize the shot for rotation and position, grow the comp by about a factor of 3, then lay big layers on top for the sky replacement and new sun. If you do that, than all you have to do is to remove the motion from the stabilized layer and put the inverse of that motion in the other layers. If you can get all the relative movement to go away, then put it back you won’t have any parallax problems…
you can also continue to track as points move off screen by holding down the option key(i think) and picking a new reference as points move off screen. You’ll see the attach point move right off screen as the track continues and the shot should stabilize.
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