track motion drift - weird

Tattoo wrote on 11/14/2004, 1:05 PM
Working on a scene where I'm using Track Motion to flow some still pictures (smaller size than the total screen) across a background image (which fills the screen). I'm using Track Motion instead of Pan/Crop so I can get the nifty 3-D shadow effect.

The problem is that my images drift as they move. For each image there's only two keyframes, a starting and ending position, and each move is either pure vertical or pure horizontal. But as the images move from start to finish, they drift towards the edge of the screen before ending in the right place.

An image on the right side of the screen and moving down, the image shifts right by a couple percent of the total screen, "peaks out" at the halfway point, and then shifts back left to finish. An image on the bottom shifts down (& back). An image on the left shifts left (& back).

For example, for a vertical move, my X coordinate starts at 56.21, and ends at 56.21, but mysteriously peaks out at 64.43 in the middle. I then added a keyframe at that middle point, and typed in "56.21". That corrected that point, but left me with two, smaller drifts on either side of that keyframe. Just plain weird.

1) Is this a bug or am I doing something wrong?

2) Does Pan/Crop not have this bug?

3) Is there an easy way to make the shadow effect if I have to use Pan/Crop?



JohnnyRoy wrote on 11/14/2004, 1:29 PM
Try setting the Smoothness to 0%. It defaults to 100% and its smoothing out your keyframes.

Tattoo wrote on 11/14/2004, 2:15 PM
That worked like a champ!

But why? ...

Ah ... I've got it now. Even though I only have 2 keyframes per image (Vegas help says "3 or more" for Smoothness to work), I have multiple images per track, and hence well more than 3 keyframes for the track. The "smoothness" is attempting to create a big looping position trace through all of the keyframes. Useful if you need it. Wacky if you don't.

Thanks, JohnnyRoy, I'd have NEVER figured that out on my own. And now I understand what the heck "smoothness" is as a bonus!

Chienworks wrote on 11/14/2004, 2:52 PM
This is another case where it would seem to make more sense to have "Event Motion" in addition to Track Motion.