The front source mesh
defines the original shape of the image in each frame of the front
clip.
To define the source mesh for the front clip:
Go to the first frame of the clip.
In the Morph menu, click Front Source.
Add a mesh over the area to be morphed
and modify its shape to match the image.
Make the front source mesh match the
image at each frame of the front clip. You can either modify the
mesh manually or use the Stabilizer to track the movement in the
front clip.