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Manipulating Motion Tracking Data in AE

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Justin LovellManipulating Motion Tracking Data in AE
by on Aug 3, 2013 at 11:00:03 am


Can anyone one help me with figuring out how to select a range of applied tracking data that is bad to connect with the rest of the good data I want. I am using AE CS6 to track motion to allow text to track off screen following a train for credits. This is a 24 second clip So I have to reposition my tracking attach point/feature as the clip plays. As I do this the tracking data is not inline with one another. I apply the data to the null and then reposition the tracking data to be inline but the data/keyframes between the two positions is a little rough and I would like to delete the bad data and connect the good. When I select the bad track key frames and delete them it leaves little red dots in between the two tracking point screwing up the speed at which the text travels across at the part of the timeline where the two positions where manually connected. Anyone have a solution I could try?



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Ivan MylesRe: Manipulating Motion Tracking Data in AE
by on Aug 3, 2013 at 3:04:04 pm

If you want to preserve the tracking points before and after the problem region, keep the bad data points and manually enter delta values using the Attach Point Offset. Usually I would try other methods first, but this might be the best solution for you.

This is the order in which I typically address the issue:

- If the problem area is near the beginning of the clip, change the motion tracker attach point and/or search region and start over.
- Use multiple motion trackers through the clip. When a tracking point starts to stray, delete the bad points at the end and start a new tracker on the last good frame from the previous tracker.
- Keep the bad data points and correct their locations using Attach Point Offset keyframes.

The most common approach is the second: use multiple tracking points. As an example, I have a three minute clip with 11 motion trackers in series.

If you do not add new trackers sequentially and the image suddenly jumps from one tracker to the other, select the motion tracker that jumps and click Apply again. This should re-position the first frame at the end point of the previous tracker. Continue through the entire clip and re-Apply each subsequent tracker.

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Justin LovellRe: Manipulating Motion Tracking Data in AE
by on Aug 5, 2013 at 3:30:57 pm

Thank you Mr. Myles,

The most common approach you mentioned is exactly what I am trying to do but how do you delete the bad tracking data if it is in the middle or at the beginning to be able to connect the rest of the data. When I open the position tab and select the bad keyframes and press delete the line is still link to the other data with small dots in between.When I play through the speed of the text pauses or slows down in the clip at that point. I tried re positioning the data points but the speed still stays the same even if I move them equally close together if that makes since. If this doesn't I can email my comp to you vie dropbox for you to see what I am talking about. Thank you for your help!

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Ivan MylesRe: Manipulating Motion Tracking Data in AE
by on Aug 5, 2013 at 5:17:42 pm

Once the data is deleted After Effects interpolates motion between the remaining data points. The bad data can be replaced using any of the following methods:

- create Position keyframes to manually move the image from frame-to-frame, or
- re-track the bad data and insert Attach Point Offset values, or
- create a new motion tracker.

The following example discusses how to replace the bad data with a new motion tracker. Consider the case where the bad data is in the middle of a tracker:


You will need to replace both the bad data and good data after the problem area:


It might require more than one tracker to fix the remainder of T2:


Be sure to overlap the trackers by one data point. Once the area is retracked, Apply in succession starting with the new tracker T4 up to and including the last tracker T3.

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Justin LovellRe: Manipulating Motion Tracking Data in AE
by on Aug 6, 2013 at 2:04:59 pm

Thanks Myles!

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