Chain tracking in Mocha

So I had a long tracking shot across a long mural on a street wall. With all the great features in Mocha, it seem that doing tracking across a pan is really really difficult. The way I do it is that I track a part, delete all the keyframes I don’t need, then track then next part, delete the keyframes I don’t need and so forth until all the parts of the wall are tracked. It is a very slow and difficult process and I had to do it five times to get it right on this shot. I was wondering if I’m missing something. I even tried the Mocha Pro evaluation to see if it does a better or somehow easier job, but it seems like it does not :frowning:

This is an easy problem to solve in any version of mocha, I am happy to report. Simply unlink the track! :slight_smile: https://borisfx.com/videos/mocha-tips-with-mary-poplin-explore-shape-based-tracking/ (Jump in around 2:10 if you already know how the tracker works).

For a long shot, make sure the surface tool is tracking into the screen and not out or your surface might go behind the camera. Usually this means tracking from the end to the beginning of the shot if you are walking forwards.

I’m not sure how that helps. What I’m really looking for is a way to limit the number of keyframes copied to only the areas that are tracked

I guess the disconnect here then is that I don’t understand why you are trying to change keyframes of the track and so I might not have understood what you were trying to do. The tracking data is all under the hood and shouldn’t need your attention barring special circumstances like correction. For tracking long shots, unlink to track is the best technique. If you’re trying to change keyframes on the shape, the question I have is why? You can just make a new shape linked to that track with minimal keyframes.

Maybe I need to explain myself better.

The shot I was working on is the last one in this movie
https://www.youtube.com/watch?v=tHzLTpYe1_k&t=3s

It took me a long time to get it right. Ended up having to individually track different parts of the mural, creating a few nulls and manually deleting a lot of keyframes. What I would like to see is the ability to either chain track a few different parts of a tracked shot to create one seamless track a across a shot where parts come in and out of it (like a drone shot over a street) and/or the ability to just export the keyframes that are being tracked and not the ones where no tracking had been done so I could easily find out where the tracking starts and ends.

Hi there,

I think you might not be understanding how the planar tracker works and are fighting it instead of working with it. This is a bread and butter mocha track that I think you can get a really good solve on quickly without deleting keyframes. Simply draw a square on the wall, go to link to track>none, mask out any occlusions to the wall like the parking sign and drag them into the layers above the track, and hit track forward using translation, scale, and rotation only and you will get a rock solid track for the whole wall. What you will see is the shape staying in the middle of the wall and if your turn the surface tool on, you will see your track chugging right offscreen. This data can then be used to drive your text as transform data on a null in AE by aligning your text and then pick whipping it to the tracking data null. Or you can use corner pins linked to the track from new layers in mocha for every text box you want to use.

Try that and let me know if you get a better solve!

Cheers,
Mary

But once the first part is gone from the screen, the tracker doesn’t know what to track, If you add another tracking, it stops after a few frames.

The shape should never move with unlink to track, the track is what moves. Try watching this very short video to see what I mean: Boris FX | Mocha Tips: Shape Based Tracking, Part 1

You’ve already sent me this video, and I don’t see how it applies, it’s for a totally different scenario.

It is not. It is for the exact same scenario, if you watch it to the end. Unlinking the track will give you exactly what you want. This video explains the difference between the shape and the track and then also shows you the unlinking dropdown in layer properties.

Please do try unlinking the track and I know you will get better results.