Motion tracking and Mask!

[jgastelb]

I'm definitely a newbie to AE. So far I'm liking it a lot. One thing that has me going crazy is the motion tracking. I have been trying to make a mask move along with a clip so I can brighten a certain part of the picture or whatever but the mask keeps moving parallel to the clip and not where I want it.

This is what I have been doing:

*Import a clip into a new comp.
*Create an adjustment layer where I create my mask.
*Do motion tracking analysis onto the clip itself at a fixed point.
*Make sure that the tracking output is to the adj layer and apply.

Like I said, the mask moves just not where my motion tracking point is. I'm sure I'm overlooking an anchor point selection or something.
Any help would be greatly appreciated.

Jgastelb

[Justin_Kirch]

You can't actually motion track a mask. You'll want to add a null layer, parent the adjustment layer to the null layer AFTER you apply all the motion tracking data to the null layer.

[jgastelb]

The null layer becomes a sort of bridge between the two then?

[Justin_Kirch]

The null layer is the only way you can allow a mask to track with motion, unless you move it frame by frame....

Trust me, just add the null layer, apply all of your motion tracking data to the null layer, parent the adjustment layer to the null layer, and voila, you have a mask that moves with your motion tracked footage.

[NickJushchyshyn]

It sounds like the issue is that you created your mask before applying the motion tracking and didn't adjust the layer's anchor point after applying the tracker.

The tracker motion is applied directly to the position of the target layer. Since the anchor point (which by default is at the center of the layer) gets moved to this position, the mask follows.

Two options to fix....
1) Apply the tracking first, then draw your mask. This way, your mask is positioned in the adjustment layer based on it's final position relative to the tracking data.

or

2) After applying tracking data to the adjustment layer, move the anchor point of the target layer to offset the mask's position so that it falls over the area you wish to affect.

Either of these approachs should take care of the issue.
Hope this helps.
Have fun.

[jgastelb]

Thanks all! Yes, this did help a lot. The issue I'm having now is that the motion tracking in 6.5 does not seem to be very accurate. I.E. I'll put the center of the motion tracking on the tip of a person's nose as they move around, still in the frame the whole time, but the motion tracking sort of loses the movement and goes off into a whole different area. I don't get it.
Jgastelb

[Sacksnack]

Expand the tracker to analyze a larger area, it will be slower but more accurate. Just the nose would be a difficult thing to track.

[NickJushchyshyn]

Thanks all! Yes, this did help a lot. The issue I'm having now is that the motion tracking in 6.5 does not seem to be very accurate. I.E. I'll put the center of the motion tracking on the tip of a person's nose as they move around, still in the frame the whole time, but the motion tracking sort of loses the movement and goes off into a whole different area. I don't get it.
Jgastelb

Remeber that the tracker is following a 2D pattern around the 2D frame.
It doesn't "see" a nose. And if there's little contrast between the color of the nose and face in general, it won't even see the 2D shape of the nose very well.

Best to track some other feature of the face and offset your mask accordingly.
Depending on the motion in your shot, the corner of the eye, or eye brow often works well, or a blemish on a cheek.