If you are trying to track a mask with SliceX and getting a poor result, please try reading the following. mocha is a planar tracker, so the shape you draw to track should be on a surface that is at least somewhat flat and moves together in one piece. So for tracking eyes, sometimes if the eye is winking you are better off to track the eyebrows or the nose and then apply an offset. Also the tracker can not track the shape changes when the eye closes so you would have to keyframe those, but mocha would track the movement successfully saving you a lot of time.
Some other examples, if you want to track someones head, just draw a shape around only the front of their face, not the whole head including top and sides. The front of the face is approximately a planar surface, which can be tracked successfully, however the entire head is not so the perspective changes will throw off the tracker.
Also, if your track shape is too small it may give a poor result, often it is better to track a larger shape and then after tracking is complete adjust the track shape to be the size of the object you wish to mask. You can adjust the shape after tracking and it will keep the track you already had.
Also if your object grows over time (gets closer to camera) then you may find you need to draw the track shape at the last frame and track backwards. This will generally give better results.
We have some specific tutorials which should help:
Screen replacement tutorial including how to avoid reflections which confuse the tracker
If you want to track part of someones body you need to break it up into individual masks, fore arms, shoulders, neck, head, chest etc and track them individually, you can’t track a body in one go because it moves separately, not as one piece.
If that doesn’t help please send us a clip showing what you are trying to track using this form, we will get back to you with specific advise.