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Tracking Rotation with Offset

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Corrado Carlevaro
Tracking Rotation with Offset
on Oct 25, 2015 at 7:19:26 pm

Hi,
I need to add a stripe along the tyre of a motorbike, rear view. I'm trying to track Position, Rotation and Scale (to simulate Z-depth)of the wheel. There are no features to track on the tyre itself, so I'm tracking the contact point between tyre and road (Tracker 1) and the rear light (Tracker 2), then I'm offsetting the Attach Point of first tracker in the middle of the tyre. BUT: the attach point doesn't stay in the line between 1st and 2nd tracker, and begins to rotate (way too much) with the 2nd tracker as pivot. I supposed the Attach point gives position data to Target layer (Null), and gets the rotation data of 2nd tracker in respect to the 1st, but this is completely wrong. I add a picture
Thank you
Corrado


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Dave LaRonde
Re: Tracking Rotation with Offset
on Oct 25, 2015 at 11:42:12 pm

The tire isn't exactly a tracking POINT. It's very wide. You would have better luck using the end of the exhsust pipe.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Corrado Carlevaro
Re: Tracking Rotation with Offset
on Oct 26, 2015 at 9:02:43 am

I'm tracking the contact point between tire and asphalt and the rear light, and they are working good, but my problem is this: I want to track the top and bottom end of an elongated object BUT get the position, rotation and scale data in the middle of that object. I add another picture.
Thanks for your help.

Corrado



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Cassius Marques
Re: Tracking Rotation with Offset
on Oct 26, 2015 at 11:12:54 am

create a null(call it "guide") and place it at your middle point, then link it to whichever tracked result you have that makes it stays there.

Then create another null and apply an expression to its position property.

a=thisComp.layer("guide");
a.toComp(a.anchorPoint)


This way you'll get rid of any parenting rotation. Now you can link stuff to this null. If you still want scale, you should link it through expressions too.


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Corrado Carlevaro
Re: Tracking Rotation with Offset
on Oct 27, 2015 at 12:26:51 pm

Not sure of what you mean with "link it to whichever tracked result you have that makes it stays there" but I'll give it a try. It's strange for me that I need a workaround to do what seems to be the most common use of Tracking Tool: track an object PSR with no useful tracking features in its center; it's not what Offset is supposed to do?

C.


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Harlan Rumjahn
Re: Tracking Rotation with Offset
on Oct 28, 2015 at 7:20:24 pm

Hi Corrado!

I think you can try using Mocha, which comes bundled with AE. It isn't a point tracker; it is a planar tracker. So you could outline the tire shape with their pen tool (called the "x-pline"), and it will track the entire oblong shape of the tire. No point-tracking involved. You then bring the tracking data back into the AE interface, and you should be able to attach whatever you want to it. Mocha is way more intuitive than AE.

Good luck!

Iggy


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