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Tracking Camera point of interest with a track point on a scene
Hello.
I have a BG plate that is one long camera pan. I have a green screen foreground that is on-camera talent. I am trying to make a “faux pan” of the talent to make it seem like they are part of the BG plate. I figured the way to do this is make a camera and adjust the Y Rotation. It looks pretty good, meaning the pan is very believable, right up until the end when the BG pan stops. It is at this point there’s a parallax shift and the BG and FG motion characteristics don’t match very well.
I have tried ease in and all that, but what I really want to do is track the motion of the real pan on the BG layer and somehow apply that to an AE camera’s Y rotation, making the FG layer 3D so that when the real pan of the BG slows down/stops my green screen FG will have the same characteristics. What I can’t figure out is how to get the degrees of the Y rotation to match the x,y tracking of the tracker.
In the AE forum, I was given the advice to animate the camera point of interest to the inverse of the tracking point. The thing is, I don’t know how to reverse it, and I can’t seem to make the math work as the distance of the tracking point isn’t the same distance as the FG needs to travel. I just want to somehow borrow the speed of the BG plate so the FG slows down and stops at the same rate.
Thanks for any suggestions.
Jeremy
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6 Replies
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can you post a screen shot? I work with syntheyes to 3d matchmove greenscreen to cgi stuff. I think you need to head in that direction because not only will you get the full camera 3d solve, you’ll also get the added bonus of lens distortion removal(which is probably half your problem)
https://technicolorsoftware.hostzi.com/
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Thanks so much for the response.
Lens distortion isn’t really a big deal on this one. Here’s a bit of an animatic and please excuse the dark screen grabs.
Here’s the “track point” I’m using:
Here’s a shot of the talent starting to creep in to the scene (rack focus done by me in post):
Here’s where she lands, more or less:
Does that make sense or do you need to see something differently?
Thanks again,
Jeremy
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1. first off, the BG parallax is shifting way different due to being farther away(AND offset) than a 3 ft away actor.
2. 2nd off, the speeds of the pans won’t even be the same.(once again by hand) that’s IF you even did a pan! If not, you’ll have ZERO parallax.
3. you have no easy tracker markers to work with anyway.
Now that you know the hurdles, here’s what you do. You 3D solve the GB panning plate then the FG plate. You now have speed data on the rate of change of the 2 camera pans. You take those Y- camera keyframes and put them into timeremap with an expression to precisely match the pan speeds. Sound easy? I don’t think so.
https://technicolorsoftware.hostzi.com/
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I failed to mention the FG scene is a lock off. I am trying to match the speed of the pan to the BG, hence my use of a camera in AE to do so.
The track works, actually, pretty well. I just can’t get the angles right.
I managed to do some sub pixel keyframing and it turned out OK, I just have to do a bunch of these in different scenes so I was looking for a tracking solution.
Thanks for the response.
Jeremy
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sorry to hear that.
if you’d had a pan, you would have at least had a prayer.let me be the bearer of bad news. no pan=zero parallax=zero changing perspective=cardboard cut out.
https://technicolorsoftware.hostzi.com/
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[Chris Wright] “let me be the bearer of bad news. no pan=zero parallax=zero changing perspective=cardboard cut out.”
OK, thanks for your help.
Everyone here seems pretty pleased.
Jeremy
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