Motion tracking working on layer but not in Comp

[celinaf66945628]

I am trying to add a circle around the lead character as he moves in the video using the motion tracker in After Effects CC 2017.  I've successfully created a tracking path (which opens up in a layer), but while it works as it should on the layer (I can see all the tracking points, which are correct), and I've tethered the path to a shape layer (which has a circle) when I apply the analysis to both the x and y axis, it renders on the composition as a seemingly completely different path.  Would anyone have advice on how I might be able to fix this or what might be going wrong?  I've tried re-tracking the path many times but it seems not to be a problem with the path.  It's approximately a minute-long video with tracking throughout.   Any help is super appreciated!

[Mike_Abbott]

My guess is:

Shape layers have a slightly complex structure: the shape layer has it's anchor point at the centre of the shape layer. However the actual shape you drew is likely not in the centre - hence they are offset when you connect the tracking data.

You can fix this in a number of ways - but probably the simplest way in your situation is as follows:

1. Apply your tracking data as you have been doing.

2. Place your playhead at the time your tracking data starts.

I'm guessing your circle is now offset from your tracking data...

3. Adjust the position of your circle to be where you want it to be, by twirling down your shape layer to:

Shape layer > Contents > Ellipse 1 > Ellipse 1 path > Position

and changing the position numbers

Preview and see if that fixes things.

If not post a screenshot here and we can take a look.

[Roei Tzoref]

Do yourself a favor and always apply transform tracking data to a null. now simply attach the layer you neef to the null. Separating the process helps you control it.

[celinaf66945628]

Hi Mike,

I tried the steps you suggested, and while the starting point now is correct (thank you), the path is not.  I'm attaching two video screencasts, one of the Comp and one of the layer with the tracking points. 

Recording #13 (Layer with tracking points) - YouTube

Recording #14 (Comp with incorrect path) - YouTube

Thanks so much for taking a look at it!

Best,

Celina

[Mike_Abbott]

Hi Celina, It looks to me like you've not done step 3?

Consider yourself at the start of Recording #14. Bring your playhead to the start of the timeline.
Now adjust the numbers for: Shape layer > Contents > Ellipse 1 > Ellipse 1 path > Position

so your circle is over the head of your target person.

NB: Roei is quite right about normally using a null object to do this - I just thought this might be a slightly simpler route in this circumstance, but I might wriote about using null objects once we've got this fixed : )

[celinaf66945628]

Hi Mike,

Here's the video with step three done (though the path is drifting upwards while the correct path on the layer is more meandering):

Recording #16 (Comp with starting point adjusted) - YouTube

I haven't used null objects before--would I need to retrack the footage in order to use a null object?  Or is there another way to possibly fix what I have now? 

Best and thanks!
Celina

[Mike_Abbott]

Ummm...

OK - without a close look I'm not quite sure what's going on - so, let's restart and do this a conventional way.

You've got your tracking data - we can reuse that.

1. Put your playhead at the time your tracking starts.

2. Create a null: Layer > New > Null

3. Put the top left corner of the null on the object you are tracking.

4. Go back to the layer you are tracking, select the track in the tracking panel and apply your tracking data (X and Y) to that null.

5. In the comp manually scrub through the file to check the null is tracking the object - if you preview the null won't be visible as it's a non-rendering object.

Do that - then report back : )

[celinaf66945628]

Hi Mike,

Here it is with the null object.  It's still tracking on the incorrect path. 

Recording #17 (null object) - YouTube

However, I did notice that when I scrub through the timeline on the layer with the tracking path, there is a tiny cross that is following the path that is showing up in the comp.  I tried to capture it in the video below.  The tiny cross is following the incorrect path, but the tracker is following the correct path.  I tried moving the tiny cross, which apparently is the attach point to the center of the tracker, but it still just follows its own incorrect path.  Any thoughts are super appreciated!  And thank you for your continued help with this! 

Recording #18 (tiny cross on the tracking path) - YouTube

[Mike_Abbott]

Ah - that's a clue.

OK - I think the issue is with the tracking itself. I wonder if you may have accidently moved the attach point (small cross)  during the tracking process.

I'd suggest you re-track. The small cross should remain central in the tracking seach boxes.

[celinaf66945628]

I don't suppose there's another way to adjust the attach point without having to retrack?  I just wonder because it took me quite a long time (maybe an hour or more) to track (and I've tried retracking three times before our conversation with the same result).  Thanks in advance!   

[Roei Tzoref]

Mike is correct, the attach point is all over the place.

I don't suppose there's another way to adjust the attach point without having to retrack?

if there was only a consistent offset, then you select all the keyframes and shift it relatively to the new position. but it seems the tracking data is messed up. you need to make sure that you only move the feature region and not the attach point. read here more about point tracking in Ae: Tracking and stabilization motion workflows in After Effects

BTW the footage is low quality and noisy, you might consider using Mocha for tracking the head.

[Mike_Abbott]

It shouldn't take anywhere near that long.

Having looked at your first video I can now see the attach point is way off to the lower right... sorry I missed that.

Let's see if we can cheat it.

1. Twirl down your layer with the tracking data on it.

2. Twirl down Track point 1

Place playhead at start of timeline / track

3. Click on the blue stopwatch for the 'Attach point' - this will remove its keyframes.

4. Click on the word 'Feature Centre' 5 lines above it. This will select all of its keyframes. Ctrl/Cmd  C to copy them.

5. Click on 'Attach point' again. Ctrl/Cmd V to paste.

Hopefully your attach point is now in the centre of your feature box.

Apply this data to your null.

[celinaf66945628 · Accepted solution]

Thanks so much Mike and Roei!  I ended up retracking, with a larger feature region and search region, and that helped speed the tracking along since I didn't have to adjust every other point.  I also made sure not to move the attach point.  It worked!  Whew.  So relieved, and grateful to you all!  I did try Mocha as well, but having to adjust the splines was somewhat cumbersome (though I'm guessing there is a better way of tracking in Mocha than I was able to figure out).