Motion and shape tracking in After Effects CS5.5 My footage consists of someone with black sunglasses moving his head tilting slowly back and forth. The glass of the sunglasses is visible in the footage. In the beginning the head is tilted back, the glasses are turned up from the camera, so only a small portion of the glass is visible. The more the head tilts forward, the more the glass approaches being parallel to the camera.

I want to track the shape and movement of the glass. So the movement would be saved to the position/rotation path and the shape to a mask shape. I have tried this using After Effects, but I only managed to track the motion of the area movement.
How do I track the changing shape of the glass as well?  I also have access to Mocha and Boujou.
I would suggest as a starting point to use Corner Pin Tracking, found on the tracking panel of AE.

Track each side of the sunglasses separately and when done, you should have two solids that move with the area of the glasses. Add a mask to each one, and rotoscope the actual shape of the glasses.

I think this would be easier than rotoscoping from scratch. These two solids can then be used as track mattes or precomposed etc.