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I'm playing around with the motion tracker, trying to track two red blobs on some PVC. As AE steps through the motion, it seems determined to move the Attachment Point increasingly off center from the Feature Region. It gets to the point where the Attachment Point is so far removed from the center that the Feature Region really isn't over the part I care to track and the whole process fails. However, fixing the region causes the Attachment Point to be in the wrong spot.
Is there a way to move the region and attachment points independently or to prevent the drift of the attachment point within the feature region?
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Your feature region is way too large. Constrain it to only the tip of the stick, not a million square miles of real estate around it. The drift happens because of this and using feature adaptation for every frame. If you realyl want to use such a large tracking region, you might at least want to turn that off (at the cost of more jumpy/ less smooth tracks, though).
Mylenium
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Thanks, that helped. I also put a white strip in the middle of the red to give it something more to grab onto. If anyone from Adobe is listening, a way to pick which channel (of RGB) you want to watch would seem to be helpful. Blender has that for its tracker (and why I went to red tape at first!).
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Although, the attachment point still drifts, even with Adapt Feature After Every Frame set to off and Stop Tracking set on when confidence drops.
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Now your feature region is too small. It should include a little free space around the whole red band.
The attach point won't move unless you move it when adjusting a track. You have to pay very careful attention to the cursor. If it turns white and the little + gets even smaller then you are moving the Attach Point.
Here are my steps for motion tracking and it always works.
That always works. When you are done, and you have attached a layer or a null to the tracker you can open up preferences again and turn on Motion Paths. Everything should be fine.
One more thing, if you have a difficult area where the feature region and the attach point get way off, you can go to the last good frame and then analyze one frame at a time. After Effects will to a lot better job of finding the feature region than you can usually do on your own. If there is some constant motion between a few frames and you just can't seem to get anything to work you can always delete the frames that just won't track and insert a few of your own. I also do that a lot of the time. If you select the Feature Center and the Attach Point in the timeline and look at the graph editor you should only see two sets of lines. Both values should be the same unless you have adjusted the Attach Point.
I hope that makes things easier to understand. Here's a crazy animated GIF of my process.
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Thanks for taking the time to write that up! I'll give it a shot!