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Ideal Camera Tracker Shape

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andy baumgartner
Ideal Camera Tracker Shape
on Jul 6, 2018 at 7:29:23 pm
Last Edited By andy baumgartner on Jul 6, 2018 at 7:31:17 pm

Hi, I'm using the AE 2d camera tracker for a scientific application to measure the rotational vibrations of a blade as it goes around a turbine.

I've been using 2 points (to capture rotation) and have been experimenting with larger / smaller single circular dots.

Does anyone have opinions about what shapes could maximize the accuracy of the track? If I use a non circular shape will that confuse aftereffects when the point rotates? If I have multiple dots inside the tracker, will that increase the accuracy?



Thanks!


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Blaise Douros
Re: Ideal Camera Tracker Shape
on Jul 6, 2018 at 9:28:41 pm

If you had multiple points within that marker, it would improve it, as would a + or x shape.


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andy baumgartner
Re: Ideal Camera Tracker Shape
on Jul 9, 2018 at 5:47:49 pm

Thanks for all the comments everyone! I will experiment with different shapes / reflective paints.


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Mark Whitney
Re: Ideal Camera Tracker Shape
on Jul 7, 2018 at 3:29:59 am

You might want to take a look at this as it goes into a lot of the thinking on shapes to use, & placement.







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andy baumgartner
Re: Ideal Camera Tracker Shape
on Jul 9, 2018 at 5:49:32 pm

Thanks! This has some great tips!


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Roei Tzoref
Re: Ideal Camera Tracker Shape
on Jul 7, 2018 at 12:42:34 pm

can we see the shot? it would help. basically experimenting is all you got, you are looking for a feature region in the search region. the more tight the feature region is, the more accurate it will be. seeing the shot will help give you the most efficient workflow

Roei Tzoref
2D/VFX Generalist & Instructor
♫ AeBlues Tutorials ♫
http://www.tzoref.com


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Steve Bentley
Re: Ideal Camera Tracker Shape
on Jul 7, 2018 at 3:07:37 pm

This is always a topic of heated debate around here. While a sphere should be the best shape because it doesn't change shape or aspect no matter its orientation, it is affected by many things - size (distance from camera), shape, once motion blur is included, extended shape, when it starts casting shadows, and shading, when the sphere has only one side lit well. On top of that, when you incorporate the square grid of pixels that make up the image it starts to no longer resemble a perfect sphere.
For projects where tracking was used for highly accurate data tables, we've used small reflective spheres (scotchlite) or spheres coated in IR sensitive paint and photographed with that type of camera and light, so the only thing you can see is a perfectly round dot. Using a highspeed camera eliminates the motion blur and the near camera lighting eliminates shadows and shape distortion. If using film, use a radial shutter (leaf) in the lens (instead of a pull down) and if using digital use a super fast chip: both to remove image smear that happens during the exposure. For highspeed use a rotating prism.



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