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!

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 :)

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

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...