Rotoscope Shifting Problem

After Effects 6.5

Alright here is the problem. When start to roto or just make changes later on in the clip it will sometimes randomly shift the mask at the begining by about 4 pixels. I cant figure out why its doing this becuase it seems to be happening pretty randomly. If you have had this happen and know why it does this please let me know.

 

This most often happens because you moved the entire mask layer accidentily, instead of just moving the control points.

Check to make sure that the position remains the same.

 

there should be a function to lock it down without locking the mask pointers, would make rotoing so much easier.

 

You should look into Zap's method.

 

Edit : Didn't mean to post this one sorry.