how do i fix failed motion track

Question

how do i fix failed motion track

Preface - I'm a noob to Motion so apologies if this is easy stuff.... 😉

I have Motion 5. I have a clip that I'm attempting to do some rotoscoping with. I'm trying to do an "Analyze Motion" behavior on the clip to facilitate that goal. I'm successful in getting the initial tracker point to the desired feature of the clip to track. The problem is that roughly 20 frames into the clip, the motion is too fast and one of two things happen (depending on how I fiddle with the tracker properties): either a) the analyze stops with the final track point on the canvas displaying as an X or b) it "locks on" to a non-relevant part of the background and never picks up the right part of the picture again.

What I would like to see is if it gets "lost", stop tracking and let me manually find the next point and then hit the Analyze button again and let it go until it gets confused again, lather-rinse-repeat until finished.

The problem is that when it ends with X, I'm not seeing how to do that. Everything I do seems to confuse it something fierce when I go to hit the analyze button again.

I'm sure I'm doing something wrong...help please?

Mac OS X (10.7.2)

Posted on Nov 26, 2011 11:21 AM

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Answer 1

GFXZen

Level 4

1,997 points

Nov 29, 2011 9:03 AM in response to aborealantelope

There's no merging to be done, you just use one instance of the behavior. For example say you have a shot that's 150 frames long. The first 100, and the last 40 frames are not a problem to track, but the 10 frame in between are giving you trouble.

-Apply the tracking behavior you need (Analyze, Match Move, Track Points, etc.).

-Mark and IN and OUT range from frame 1 to 100, then analyze that section. Once that is complete...

-Mark an IN and OUT range from 111 to 150, then analyze that section, use the same behavior. Once that is complete....

-Mark an In and OUT range from 101 to 110. Try any of the changes I mentioned above, and analyze.

By using the in and out play range you "protect" your good keyframes, if things go wrong, you can use the play range as a guide and go to the keyframe editor and delete bad keys and try again or as you mention, manually clean things up. Because you use one instance of the behavior all the keyframe are together. This is one of the benefits of the tracking behaviors most people don't realize, you can break the analyis up, or even come back and redo section you think don't work well.

Good Luck!

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Answer 2

Nov 27, 2011 7:41 AM in response to BenB

@BenB yes, I read that but I'm apparently not understanding it or I'm doing something wrong. After the 'X' appears I'm backing the frame up to the one that failed and then manually positioning the tracker onto the desired feature's current position in the clip. If, at this point, I press the 'Analyize' button again, it completely loses the tracked feature and the keyframes stay in one spot for the rest of the clip if I just let it go. I've even tried to doing the 'hold option down while positioning to give it a look-ahead frame hint' trick.

This may simply be a matter of the object I'm trying to track being too small, moving quite fast and irratically and being too small in the frame for it to be able to distinguish it well enough...but even so, there are stretches of 20-40 frames where it does just fine so I'm willing to manually keyframe those portions where it gets confused because those stretches of 20-40 frames will still save me a bunch of time, but I can't seem to get it "back on track" (pardon the pun) after I start manually giving it help.

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Answer 3

GFXZen

Level 4

1,997 points

Nov 28, 2011 7:32 PM in response to aborealantelope

You are correct, small, fast moving reference points can be tricky, but here are a few things you could try:

-Isolate the track, turn off addtional tracks and work on individual points.

-Break your track up into section with the IN and Out markers. Get the easy sections done and then isolate the difficult sections and try the settings I mention below.

-Increase the search size for the track that is giving you problems. I do this often with elements that move quickly across the screen.

- Try using the different Fail behavior settings. It sounds like you may want to use "Stop" or "Predict and Key" options. The latter should drop more keyframes if you fail and this would allow you to manually adjust with the on screen controls.

-Increase the fail tolerance (90-99%). This will decrease the likelyhood of grabbing the wrong point and stop analysis more quickly.

-Decrease the fail tolerance if you just want to drop keys and manually adjust the frames, set the value low so keys are added and you can then manually tweek them.

-Once most of the tracking is complete you could convert the behavior to keyframes, select the shape and adjust the control points with Record Animation active.

As a final tip, when rotoscoping you can use the Shape>Track Points behavior and use it to do your analysis. This will simplify your setup.

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Answer 4

Nov 29, 2011 3:32 AM in response to GFXZen

I hadn't thought of breaking it into chunks...is there a way at the end of the process to merge those groups of keyframes into a single continuous set of points? That would make assigning them as a match move or using shape track points easier...

Thanks!

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Answer 5

BenB

Level 6

13,222 points

Nov 27, 2011 7:06 AM in response to aborealantelope

http://help.apple.com/motion/mac/5.0/en/motion/usermanual/#chapter=22%26section= 14

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