Reverse Motion Tracking, After Effects& Mocha Pro

Hi Folks,

I’m learning how to use Mocha Pro to take my plate of a subway car that’s bouncing around, track the car’s movement, and then remove the movement to do compositing. In this case, to mask off the subway car’s windows. I’ve watched Mary’s video on this (Mocha for After Effects: Reverse Motion Tracking with Power Pin - YouTube), but maybe since I am not just painting but also rotoscoping I am having problems. I have attached a screen grab. Please tell me where I went wrong and how to fix this problem.

  • The motion tracking went great.
  • I applied the motion tracking (inverse) to the plate. It is rock stable. Yay!
  • I rotoscoped the windows (purple and pink mask outlines) as they closed- and they look great! As you see, they are in the right place.
  • But the black stuff (background) showing through is in the wrong place.

Help, please!

Thank you.

If it helps, here’s a screenshot that shows I have put the rotoscoped layer into a precomp, unchecked “invert” in the MochaPro plugin, and applied that as a CC PowerPin to the layer. This is what I get. The roto parts are just… wrong. It looks the same if I do her second way, which is to copy CCPowerPin, apply it to the precomp, and click unstretch: the frame stretches out to its original dimensions, the movement comes back, but the roto shapes in AE do not work right.

Eek. Help appreciated!

I believe I have a solution. It worked when I pre-composed not just once but twice. First apply the power corner pin, then pre-compose that. THEN do the roto of the windows to that pre-comp. THEN pre-comp the roto’d pre-comp. THEN apply the transform data. Voila!

Sounds like you solved it!

The problem is applied AE masks don’t affect underlying renders, so if you’ve rendered a stabilize, the AE mask will be taking the data from the original track.

So precomping and then masking is a good way to do it