I'm currently attempting to apply a blur effect to around 3 - 4 licence plates of cars parked next to each other, whilst the main character is standing in front and is putting on a bike helmet. I've been using adjustment layers and the AE standard motion tracker, but as soon as my character's arm sweeps past one of the track points the tracker loses its place and ruins the tracking. The character takes up a lot of the shot so there are very few options to use as tracking points - hence I need a way around this.
Is there a way to track motion for a point (or 2 points if using rotation tracking too) up until a certain time in the clip, and then use a different couple of points which aren't covered by an arm to continue tracking the motion for the same adjustment layer? Or will I need to use separate adjustment layers for each set of points?
Not at my computer at the moment so I can't double check but I believe you want to hold Ctrl/Cmd (Mac/PC) and drag the feature rectangle (or possibly the search rectangle, either way one of the rectangles) to a new feature. The feature center (where the track points appear) should not move.
Try to pick a feature that is the same distance from the camera so that parallax doesn't throw your track off. I'd also move back to your original feature when it's no longer obscured.
Your workflow has more twists and turns than a bag of curly fries! ;-)
You have multiple issues as a result of having to track a region(s) with occasional occlusion(s).
Forget about Adjustment Layers for this task. Unless you are using a script that tracks mask, you should only apply one mask onto one adjustment layer - NO to multiple masks on a single Adjustment Layer.
If your tracking region gets occluded, by a foreground object, then switch to Offset Tracking. You initiate Offset Tracking in AE by ALT+dragging the Search and Feature regions onto an area that is identical, relative to the inherent movement of the original tracking region and the camera's movement.
When ALT+dragging the Search and Feature regions, ensure that you DO NOT move the Attach Point from the original tracking region.
Lastly, you should be looking at using mochaAE/mocha Pro. mocha has the advantage of tracking multiple regions at one go. You can also first track a Holdout Matte, the foreground object (character) that occludes your multiple tracking regions, and then use this Holdout Matte (track it only once), multiple times for each of your actual/desired tracking regions.
Let us know if you have more Qs, but please do as much work on your end first as it seems that there is a lot of RTFM that is required on your part.
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Cheers both, I've had a play around with the alt+drag and found it to work perfectly. I've heard about Mocha and will do a little digging around it in the near future when I require more motion tracking.