Tracking Malfunction

Having bizarre errors in tracking with Mocha in AE.

I did most of the tracking spline of an object in Mocha. I had to go back at various spots and edit the spline points to track better.

Once I did that, all hell broke loose. Suddenly at odd frames the spline points scattered all over the place. I did not touch them. I merely moved points of the spline many frames away from any edit.

So I go fix them, but that then causes other frames to have scattered spline points… It was then I checked the matte in AE and it at times jumps around, even though when I go to Mocha there seemed to be no problem with the spline.

It’s a fool’s game to continue as every fix yields new problems. And unfortunately this is a complicated rotoscope that I spent hours on and don’t want to lose.

So, how can an edit in a spline affect the spline 100+ frames away?

And back in AE it looked like maybe the matte did not match the spline point for point, accurately. That could just be those points in Mocha jumping around, tho at the time I went to AE those points were likely fine.


Hi there,

This sounds like data corruption.

Make sure you can see your surface tool for the entire length of the track, you might have the surface behind the camera and that will generate many errors as Mocha can’t calculate anything that moves “behind the camera” plane. Try tracking up to shear but not perspective as well and see if that can recover the shape for you. Even if the surface tool is turned off visibly, it can still make your shape go haywire if it goes behind the camera.


Umm…seems there is no surface tool. Is that bad? :wink: Not sure how that happened.

I tried re-tracking, but those periodic wacky splines are still there. So, 90% of this spline now used only for a matte that will be created is fine. I suppose I could try to manually re-adjust those, without re-tracking.

Moving from 1 frame to the next with play vs track I take it matters, as in tracking the frames are linked/inter-dependent?

Actually, how does the tracker work in regards to frames being inter-dependent? Is the prior frame(s) used to calculate the next frame being tracked? They are not independent single frames, right?


Yeah, that’s not great, but try this. Try using the align to surface tool on the first frame and see if the surface tool will reappear for you. Then try moving your surface tool to be smaller and more parallel to the camera, then try retracking. Sometimes you can recover the shape that way.

Play and track do different things, play just plays the video back, track actually writes or rewrites tracking data.

The tracker works by using the search area of the shape to identify a texture, then it looks for the texture on the next frame and how that texture is shifted, then it pulls the shape and surface tool to that location and transforms it accordingly. Then the process repeats with some intelligence for over time correction. The track writes a keyframe for every single frame, but I would not call it independant, it’s based on all previous keyframes as well.

Anyway, try adjusting the surface tool and see what you can get. Or simply export the data to AE as a shape and delete the bad keyframes.