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Mocha Adjust Track Module problems
I’ve run into this problem before and always just dealt with it, but I really want to know what’s happening.
I’m tracking a card that someone is holding (3′ square) to insert video onto it using a corner pin. The initial track is ok with a little bit of drift, so I jump into the Adjust Track module. After setting the Master All, I go through and adjust points as usual. However the problem is that sometimes, after adjusting a point that has drifted back to where it should be, the point then immediately jumps back to where it had drifted to on the next/previous frame.
I’m setting keyframes as I normally would – adjust point to the correct location, move through the clip until the point is at it’s “worst” drifted place, then adjusting again, and so on. But then in between the two set keyframes, there is still a bit of drift. So I go to the worst place in between, set another, etc. Sometimes I’ll have to set many keyframes, because even if I’ve adjusted correctly, the point just jumps right back out of place on the very next frame.
It seems to me like Mocha isn’t interpolating keyframes properly, but in reality I’m assuming that it’s just not interpolating them as I’m traditionally used to keyframes being interpolated in AE, etc. I’ve heard it said that if this happens, then you probably just have bad initial track data, but I really don’t think that’s the case. The track is good enough that if I used just the translation data to roto in AE, I’d only have to adjust a few mask keyframes on my matte layer, but this Adjust Track for a corner pin is driving me b-a-n-a-n-a-s.
Does any of this make sense to anyone? Would it help if I posted a video screen cap of this actually happening?
Thanks in advance! Cheers!! -
8 Replies
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Hi Gardner, based on your post, I don’t see where you’ve followed my instructions in this thread – https://forums.creativecow.net/thread/2/1046602#1048423.
You seem to have missed the part in step (2) where you create the second keyframe in the Adjust Track module.
The Adjust Track module does what it says – it adjusts the ‘original’ tracking data. Once you’ve anchored the timespan where drifting occurs, with the TWO keyframes, you will not experience the issue you’ve described. Without this anchoring keyframing strategy, you will inadvertently adjust the ‘original’ keyframes, over a timespan, that had provided you with a solid track.
Of course, there is very much a need to create additional keyframes within the anchored timespan. You seem to have the keyframing strategy for this part sorted out.
HTH
RoRK
Latest AE Workshop – MoGraph Intensity – Shapes & TextIntensive mocha & AE Training in Singapore and Other Dangerous Locations
Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI -
Thanks for the quick reply. Perhaps I’m just confused, but what happens when the point in Adjust Track drifts off the point permanently and not back to a good point? Where do the “anchor” keys get set? In this particular corner pin track, the point stays in the correct position for about half the shot, then drifts to a new spot, and more or less stays there for the remainder.
Using the described method, I would think to
-set my Master Frame at the beginning point of the shot, continue to the frame just before the drift begins, and set another
-continue to the point where the drift more or less stops, and set a new frame with a new adjusted point
-work in between the last two set keyframes to fix any additional driftMy problem occurs in between these last two keyframes. Inevitably there is a little more drift to get fixed, and when I start adding additional keyframes (always first at the “worst” drift point), this issue of “jumping around” crops up. This morning after your reply, I re-tracked the footage and really paid attention to my keyframe strategy, but I’m still having the issue, though this time, it’s a different corner.
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You really have to read these again – from the link I gave in my last post.
1) make a note of the timespan where the tracking anomaly occurs
2) in the Adjust Track Module, set a keyframe ONE FRAME BEFORE and another keyframe ONE FRAME AFTER the timespan that you noted in (1)HTH
RoRK
Latest AE Workshop – MoGraph Intensity – Shapes & TextIntensive mocha & AE Training in Singapore and Other Dangerous Locations
Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI -
Roland,
Again, I appreciate your input. I don’t mean to sound like a jerk here, but I completely understand what you suggested before, and that’s how I work when I’m using keyframed data linked to tracking data – in Mocha or doing roto work elsewhere. You use the “good” frames as anchor points on either side, and adjust the most drifted/”worst” frame in the middle, and cut down your problem areas by essentially half each time. Once you get the frames in enough good places, the program should interpolate the in-between motion correctly.
BUT, this isn’t what is happening for me. Even if there is still a drift problem in between two good keyframes, the point should drift back to the “bad” point somewhere in between the good ones, not immediately jump back to the “bad” point on the very next frame.
I understand how this could be confusing reading my description without actually seeing it happen, so please let me know if a screen cap would help, or if you have any other ideas.Thanks
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Gardner, everything you’ve written makes sense except for the bit below –
[Gardner Raymond] ” Even if there is still a drift problem in between two good keyframes, the point should drift back to the “bad” point somewhere in between the good ones, not immediately jump back to the “bad” point on the very next frame. “
See if the following helps –
Once you’ve got two ‘good’ KFs anchored, every KF in between will have a high probability of being ‘bad’ – this includes the KF after the first anchor KF and the KF before the last anchor KF. This is expected behavior.
I can only appreciate an anomaly if the KF just before the first anchor KF became ‘bad’ and/or if the KF after the last anchor became ‘bad’. IOW, after creating your anchor KFs that defines a timespan, are the KFs outside of this timespan affected.
Can you confirm on the anomaly?
By all means provide a QT screencap and post it here. But it’s 4AM where I’m at – so I’ll take a look at it later in the morning.
HTH
RoRK
Latest AE Workshop – MoGraph Intensity – Shapes & TextIntensive mocha & AE Training in Singapore and Other Dangerous Locations
Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI -
Roland,
You are correct – there is no anomaly outside of the KF rage, only within.I guess my confusion comes from the way I expect the KFs to correct the motion, and they way they actually do. I understand that the positions in between the good KFs have a higher probability of being “bad”, as that’s where the drift in the original track occurred, correct?
When it comes down to it, I just want to get the adjusted track to be correct with as few keyframes as possible. Do you (or anyone else reading this) have any suggestions for this besides trial and error?I’ll post a screen cap in a bit when I get another few free moments. In the meantime, to further clarify (or confuse) things, here’s the most accurate way I can think to describe what’s happening:
-Say that the whole clip is 30 frames
-The tracking point of corner 1 of the surface is correct from frames 0-10 at XY position (0,0), and is correct again from frame 21-30 at (0,0);
-it drifts up and right between frames 11 and 20, with the “worst” position being at frame 16, having drifted to (10,10);
-I set a “good” kf at frame 10, and another at frame 21;
-I go to the worst drift frame of 16, and adjust the point to be back where it should be at (0,0);
-Now, the point is adjusted correctly between frames 16 and 21, and the drift is corrected. However, if I back up in the timeline one frame from my adjusted one to frame 15, the point immediately jumps out of location, back to (10,10), and then slowly goes back to it’s correct location as I continue backwards to frame 10.
-many times when this happens, the only way I can get it to say in the correct location is to set a new kf on (nearly) every frame in between, and I know this isn’t the best method (and defeats the point of tracking!)Thanks again for your help, and especially at such an hour! If anyone else has any thoughts, they’ll also be very appreciated.
Cheers, all!
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[Gardner Raymond] “However, if I back up in the timeline one frame from my adjusted one to frame 15, the point immediately jumps out of location, back to (10,10),”
It’s strange because you’ve got everything correct until the part above. Based on what you’ve written, the only thing you’ve done between frames 10 and 16 was to set an anchor KF at frame 10 and set a good KF at frame 16.
You’ve not mentioned if you created more KFs between frames 16-21 other than that the results of the track in the said timespan looks fine. Perhaps if you understand that mocha’s KF interpolation defaults to linear interpolation may help PLUS the fact that drifts that occur within a timespan may likely be non-linear – ie the drift may be more pronounced at the beginning of the timespan and less pronounced at the end. It’s like using AE’s ease Temporal KFs.
Everything seems fine in how mocha is working. As for your Q on how to reduce KFs, this was already covered in the other thread that you started.
HTH
RoRK
Latest AE Workshop – MoGraph Intensity – Shapes & TextIntensive mocha & AE Training in Singapore and Other Dangerous Locations
Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI -
Hi Gardner, here’s another tip (I’m not sure if it was mentioned in the earlier thread) that’s quite useful.
Using your example – frames 11-20 exhibit tracking drift. Place anchor KFs at 10 and 21 (you know this already). Then correct for drifts at frames 11 and 20. Then follow through with identifying a frame with maximum drifting and correcting that frame. Repeat the identification for max drifts between a new corrected frame and either its previous or next corrected KF.
HTH
RoRK
Latest AE Workshop – MoGraph Intensity – Shapes & TextIntensive mocha & AE Training in Singapore and Other Dangerous Locations
Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI
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