11-19-2009, 01:23 PM
A bit hard to tell without seeing the footage, but I can recommend a few possibilities:
You may not have enough points of contrast in the scene. The tracker works by searching for planar areas of texture detail so if your footage has no contrast it can drop the track. You can also try tracking with channel contrast instead of luminance.
Something has moved into the search area. You will need to mask this out either with another contour or a separate layer. Although mocha is fairly forgiving of anomolies entering the search area, it can help to mask out any objects entering. This includes reflections, as mocha can confuse this for a separate plane.
A vast amount of rotation or zoom occurs in the shot. If this happens you can tweak the zoom and angle parameters to give it a helping hand.
The area you are tracking has gone out of shot. You may need to find another relative plane to keep tracking with.
A vast amount of motion blur. Mocha can usually handle a severe amount of blur, but not in all cases.
If you are finding it slow or difficult to maintain a track, break your search area into smaller chunks by creating an area with the spline tool, then further areas with the "Add spline to layer" tool. You can also try ramping up the "min % pixels used" value. Quite often these two techniques can lock down a lot of problem tracks.
If you can't resolve with any of these, you may need to track up to the point where you lose the track, switch to manaul tracking for the problem frames then switch back at a stable point. You can then use adjust track to fix any drift.
If you can, post a link to an example footage or attach stills of the problem area.
11-19-2009, 03:10 PM
the auto channel trick worked great.
Thanks for you help it was really great to have several tips incase I run into other problems and have no idea how to go about solving.
Now I know what to try!
11-19-2009, 03:10 PM
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