Apple Motion Tracking and Lens Field Curvature

Hi All,

I am using Apple Motion (5.5.3) to track the position of a window as I pan across the room. Tracking does work some what. However, it seems to be unable to deal with the field curvature of a 12 mm lens on an APS C (18 mm equivalent on full frame).

If I add 1 tracking point, Apple Motion seems to do a good job tracking that point.  The moment I add another point, the first tracking point no longer tracks and the second point will get a good track.  While both are high enough contrast points to motion track by themselves, the moment I add another point, the first tracking point no longer tracks.

Can any one shed some light as to what might be going on.

Don

If you don't get a response here you could post to the Motion community in the Apple discussion forums.

Hi Terry,

Thanks for writing, After more experimentation I am getting the impression that Motion only tracks the last point you select. If I review the Track Preview for the previous point selected, the track on that point is rapidly lost with the first movement of the camera.

Don

have you tried Motions 4-Point-Tracking?

help.apple.com/motion/mac/5.0/en/motion/...apter=22%26section=8

HI Karsten:

I had not tried 4 point tracking associated with Match Move. I just tried It and it works well. Thank you for the suggestion.

But this solves only a potion of my problem.  Sometimes I have more complicated shapes where I want to track a mask. For example, let's say I have a chair in front of window. Then the 4 point method will not be adequate. Ultimately, I may require 5 or more points to properly describe and track the mask.

My test of two points using Motion Tracker shows that only the last point selected is tracked. Do you have any suggestions?

Don

Hi Karsten:

I am developing the impression that I am unable to do get Apple Motion to track a mask to a multi-point Analyze Motion. This what I am doing:

1) Apply Analyze Motion to an Object.
2) Select 5 points to track and then select Analyze..
3) Create a Bezier Mask.
4) Apply Match Move to Bezier Mask.
5) Use Analyze Motion as the source for Match Move for the Bezier Mask and select Position and Scale.

And this is where I run into problems. In Match Move I can only select 2 of the 5 tracking points: 1) Anchor and 2) Rotation Scale. Unfortunately, two points are not enough to describe the field curvature as I pan across the window.

I believe this to be the reason why I am unable to create a 5 or more point mask that tracks the subject.

Do you, or does anyone, have a suggestion on how to overcome this issue?

Don

Hi All:

After doing more web research it seems I am attempting to do something similar to Rotoscoping. Apple Motion is most likely not the best application to accomplish this. Follows is a website that shows a potential workaround:



Have not tried this yet.

I also found this website that identifies several rotoscoping applications: thegeekpage.com/rotoscoping-software/

As suspected some of the applications mentioned are AfterEffects, Blender and Fusion.

Has anyone tried Davinci Resolve/Fusion to accomplish something similar to what I am trying to do?

Don

Hi All,

I now have a solution for Apple Motion.

Do not use Match Motion as a behavior for the mask. Instead, use the behavior Shape/Track Points. As long as the vertices on the mask are the same as the same tracked points in the behavior Analyze Motion, then one gets a mask that tracks correctly and scales properly to account for field curvature.

Thank you to fox_m on Apple Support Communities for this suggestion. Also, thanks to Terry who suggested Apple Support Communities and to Karsten for his suggestion on 4 point tracking. Without either of your suggestions, I never get to the point to properly pose the question that resulted in getting an answer to solve my problem.

I hope this information helps others on fcp.com

Don

Have you looked into TrackX by Coremelt?

Hi Ben,

I have not.  Thank you for the suggestion.  What can it do versus what is available in Motion?

Don

It is a much more advanced tracker (Mocha planar tracker).

HI Ben:

From other posts, I know that you have been considering making a transition from FCP to Davinci Resolve. How does the tracker in TrackX compare to Resolve/Fusion?

Don

dgbarar wrote:

How does the tracker in TrackX compare to Resolve/Fusion?

I have no clue, not done a one-to-one comparison yet.

Hi All;

While Shape/Track Points does work, it begins to have issues as the tracked points move out of the field of view.

For example, let's say that in your scene that you pan across a window that is masked. Shape/Track Points works well in adjusting the mask position. However, as the window moves out of the field of view, the leading track points are lost and begin to move to a position that results in the mask being distorted. Ideally, what I would like to happen is for Motion to extrapolate the position of the points after they leave the filed of view.

Has anyone encountered this? How do you deal with this situation? What other plug-ins would work to help with this situation?

Don Barar

I am not aware of any tracking solution that can interpret sync on an object that is no longer in the frame. I would suggest cutting the clip at the point just before the window's tracking points go out of view, and then choose another object in the field of view to track for the duration of the clip. You would treat this subsequent section as a new clip and reapply your tracking. In some cases, I have had to blade a clip 3 or 4 times and reapply tracking locked to different parts of the visible image.

HI DGW:

Thanks for writing.

I thought about your suggestion as well--blading the clip just as the first tracking points of the window went out of frame and do another track.  Unfortunately, there are no high contrast tracking points as the window moves out of frame to maintain the shape of the mask.  Even if there were tracking point close by, they too would move out of the scene and necessitate me splitting the remainder of the clip every frame until the window was completely out of frame.

Here's an opportunity for a new tracking plug-in that perform this extrapolation of the tracking points.

Don

TrackX let's you track to and from specific points, then manually keyframe between.

Hi All:

I attempted masking/tracking a window that I was panning across that eventually went out of scene using Davinci Resolve 17.3. No issues and no additional key framing. The window moved out of scene and the mask did not distort. Worked great and was such an easy thing to do.

Can not even begin to understand why Apple can not provide this type functionality in Motion and FCP without having to resort to a third party plug-in.

Don

Send Apple your feature request. The more people who ask, the more likely it percolates to the top of the list. Final Cut Pro->Provide Final Cut Pro Feedback...

Hi Terry,

My impression is that Apple is not doing many feature requests these days for the pro applications. But wait. They are making some upgrades to FCP. Gee did they not recently change the blade tool to scissors?

Don