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tracking a fast moving dot

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James Pierson
tracking a fast moving dot
on Jan 23, 2014 at 3:00:14 pm

Hello,

I'm looking to track a fast moving red dot inside after effects, I must admit I've not had a lot of experience with tracking, but I would have thought (probably naively!) that although the dot is moving fast, its not blurred and its on a plain white background, it must be fairly simple to do?

I've uploaded an mp4 of the red dot im looking to track:

7034_reddot.mp4.zip

its only 5 seconds long. Every time I try and track in after effects it tracks for a few frames then drifts off. I can change the colour of the dot/background if that helps? I can also render with alpha so theres no background if that would help after effects track it?

Thanks in advance!
James


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Declan Smith
Re: tracking a fast moving dot
on Jan 23, 2014 at 3:42:27 pm

I've tried tracking this in AE and it does a reasonable job, but as you say, it loses it. What I would suggest is that you have a fairly large outer bounding box so that AE has a fighting chance of registering the movement. I notice that there is at least one frame where there are two dots, which confused the tracker.

It would be best fro track, one frame at a time, and as soon as AE loses the track, correct that frame.

Also the dot changes shape from a circle to an ellipse which helps the tracker lose focus,

Declan Smith
http://www.madpanic.tv
After Effects CS6/ FCS3 / Canon XLH1 / Canon 7D / Reason / Cubase

"it's either binary or it's not"


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James Pierson
Re: tracking a fast moving dot
on Jan 23, 2014 at 4:27:29 pm

Hi Declan,

Thank you for taking the time to respond. Effectively what im trying to do is animate a whiteboard style animation in after effects.

Ideally i'd draw the characters inside illustrator with the line/pen tool, copy this into after effects as a mask, apply the stroke effect, reveal the line, and then copy the mask path properties onto the position layer of a hand holding a pan, sync up the key frames so it looks like the hands drawing out the image.

Its all great in theory but the problem I get is when I copy the path from illustrator into after effects, it comes in as 50+ masks(unfortunately trying the 'unite' function in illustrator doesnt help either)as the image is complex. This is fine to apply a stroke to, but I can't copy the mask path properties of each mask path into the position of the hand as its to time consuming and also would be difficult to sync up properly if I was using easing etc.

So! What I wanted to do, was to copy the path from illustrator to after effects, apply the stroke effect to 'all the masks' to get a nice reveal. I then duplicate the layer, and make the line colour vivid (in this case tried red) and thicken up the line. Now, rather than reveal all the lines as if being drawn out, I tried to make it so the stroke 'start' and 'end' keyframes made a dot that zipped along the front of the path.

I would then export this as a png sequence or mp4, bring it back into after effects, lay it over the initial image being drawn out, track the red dot data, then apply it to the hand image and hey presto it would follow along.

I've done white board animations inside after effects before by having the image I want to reveal, drawing a mask by hand over the top of it and applying stroke to it, to then copy the mask path into hand position. I'm certainly prepared to do it that way again, but I found its slightly time consuming, and when lines intersect it can be a little messy.

I just thought it seems like the answers so close what with illustrator/after effects path compatibility, but I can't figure it out! I was hoping it would be simple to track a red dot on a white background and my problem would be solved, but if I have to track the dot by hand every time it drifts off course then that would probably be more time consuming than my old method.

Any comments/work arounds I'm not seeing would be greatly appreciated!


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John Cuevas
Re: tracking a fast moving dot
on Jan 23, 2014 at 6:04:07 pm

I just tracked the dot, it took a couple of minutes, it only lost the dot a few times, when it did I stopped and re-located the tracker...

I just thought it seems like the answers so close what with illustrator/after effects path compatibility, but I can't figure it out! I was hoping it would be simple to track a red dot on a white background and my problem would be solved, but if I have to track the dot by hand every time it drifts off course then that would probably be more time consuming than my old method.

---that's part of tracking.

7035_dottrackedfolder.zip

I basically did what Roland suggested, it took a couple of minutes, it only lost the dot a few times, when it did I stopped and re-located the tracker...

Johnny Cuevas, Editor
Thinkck.com

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.


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Roland R. Kahlenberg
Re: tracking a fast moving dot
on Jan 23, 2014 at 4:59:36 pm

This should be doable in only a few minutes.

Set your tracker as such NEFORE tracking -
1) Tracker Panel - Options section
a) Switch on Adapt Feature on Every Frame
b) "If Confidence is Below ...%" set this to 90
c) Set (b) above to "Stop Tracking"

2) In the Timeline, twirl Motion Tracker Properties until you see Search Size, set this to [250,250] or even [300,300]. YOu can of course adjust the size of the Search Region in the Layer Panel but in the Timeline, you can put in precise numbers which then gives you an idea of how much to adjust this prop should the tracking target move too much from frame to frame.

3) Begin tracking. Keep an eye to make sure that the tracker is doing its job well. Should tracking stop [due to (1c) above] or if you notice that the tracker is inaccurate, then manually move the Search and Feature Regions and Attach Point to their correct location. Then track one frame at a time for a couple of frames. If all goes well, then continue tracking at 'normal speed'.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI


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Darby Edelen
Re: tracking a fast moving dot
on Jan 24, 2014 at 12:38:40 am

Honestly stepping through this footage one frame at a time this looks less like a fast moving dot and more like a randomly moving dot :)

Since you're generating this dot in AE, why don't you slow it down some? Instead of animating over 2 seconds try 10, 20 or more seconds. Once you have your tracker keyframes you can always collapse them down to 2 seconds (if that's the speed you need).

Also AE's tracker tracks by luminance by default so I'd recommend just rendering a black dot on white. The only case where I'd recommend using colors is if you need to track more than one dot at a time in which case you can change AE's tracker to track by RGB rather than luminance (which may take slightly longer to track).

Darby Edelen


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