Motion Tracking in AE at DVinfo.net

Jon Fairhurst · February 9th, 2010, 11:20 PM

So... I've figured out how to do motion tracking in After Effects, but I'm having trouble figuring out how to deal with stabilizing to a background that gets occluded at times and in various parts of the screen.

In particular, I'm "gluing" a user interface to a screen in a handheld shot. It's green, so there is action in front of the screen. I can corner pin, but once my reference point is obscured, things go nuts.

One thing that would help is if I could figure out how to erase a group of keyframes. Let's say my track is perfect for two seconds, but a 2;01 it goes haywire. How do I easily delete just those keyframes? If I can do that, then I can use a different set of reference points and go forward, until the next screw up. Eventually I'll get to the end.

Similarly, sometimes a corner goes out of frame. Any ideas for that case?

Thanks in advance!

Richard Wakefield · February 10th, 2010, 05:51 AM

hey Jon

i think at one point or another (pun intended!!), us AE users have all had the same problem. annoying isn't it!

but there is a workaround. you can track something until it goes off screen, then carry on by combining it with a new tracking point. You combine motion trackers into a null object.

i can't explain it in text, but as always, andrew kramer comes to the rescue! can't quite remember which tutorial it was that covered it, but i have a hunch it was the one on set extensions:

VIDEO COPILOT | After Effects Tutorials & Post Production Tools
good luck!
Richard

p.s. to delete keyframes, you simply click on them (or highlight several) and press delete :)

Steve Kalle · February 10th, 2010, 04:32 PM

You can easily delete the keyframes from the tracking. Select the clip and hit "U (you)" which shows all keyframes.

I am a current member/student at FXPHD.com and recently saw an example of what you want to do. If I remember correctly, he ran the tracker, stopped it and deleted a few keyframes, then went ahead several frames and started the tracker again.

The videocopilot tut could be this: VIDEO COPILOT | After Effects Tutorials & Post Production Tools

Jon Fairhurst · February 10th, 2010, 10:39 PM

Richard,

That was perfect. The null object trick is just what I needed to learn!

Also, I figured out how to delete a subset of keyframes - you just drag a box around them with the mouse and hit delete.

Now, back to my compositing...

February 9th, 2010, 11:20 PM	#1
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	Motion Tracking in AE So... I've figured out how to do motion tracking in After Effects, but I'm having trouble figuring out how to deal with stabilizing to a background that gets occluded at times and in various parts of the screen. In particular, I'm "gluing" a user interface to a screen in a handheld shot. It's green, so there is action in front of the screen. I can corner pin, but once my reference point is obscured, things go nuts. One thing that would help is if I could figure out how to erase a group of keyframes. Let's say my track is perfect for two seconds, but a 2;01 it goes haywire. How do I easily delete just those keyframes? If I can do that, then I can use a different set of reference points and go forward, until the next screw up. Eventually I'll get to the end. Similarly, sometimes a corner goes out of frame. Any ideas for that case? Thanks in advance! __________________ Jon Fairhurst

February 10th, 2010, 10:39 PM	#4
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	Richard, That was perfect. The null object trick is just what I needed to learn! Also, I figured out how to delete a subset of keyframes - you just drag a box around them with the mouse and hit delete. Now, back to my compositing... __________________ Jon Fairhurst

February 10th, 2010, 05:51 AM	#2
Richard Wakefield Major Player Join Date: Feb 2006 Location: Surrey, UK Posts: 680	hey Jon i think at one point or another (pun intended!!), us AE users have all had the same problem. annoying isn't it! but there is a workaround. you can track something until it goes off screen, then carry on by combining it with a new tracking point. You combine motion trackers into a null object. i can't explain it in text, but as always, andrew kramer comes to the rescue! can't quite remember which tutorial it was that covered it, but i have a hunch it was the one on set extensions: VIDEO COPILOT \| After Effects Tutorials & Post Production Tools good luck! Richard p.s. to delete keyframes, you simply click on them (or highlight several) and press delete :)

February 10th, 2010, 04:32 PM	#3
Steve Kalle Trustee Join Date: Aug 2009 Location: Chicago, IL Posts: 1,554	You can easily delete the keyframes from the tracking. Select the clip and hit "U (you)" which shows all keyframes. I am a current member/student at FXPHD.com and recently saw an example of what you want to do. If I remember correctly, he ran the tracker, stopped it and deleted a few keyframes, then went ahead several frames and started the tracker again. The videocopilot tut could be this: VIDEO COPILOT \| After Effects Tutorials & Post Production Tools