Changing the corner radius of a mask in After Effects can be done only while drawing that mask (use the rounded rectangal tool – under mask tool). Use ‘arrow up’-key and ‘arrow down’-key to change the radius. Once you let go of the mouse button you can’t change it anymore.
You may also like
Photoshopped from a studio shoot.
A stop motion animation I made for ‘De Bijenkorf’.
Choose Orient Along Path
To render an alpha channel with your video, set the ‘depth’