From your example it looks like the transition is done over a character that stands still- that makes it easy. If you do not have access to a 3d app, then you can draw a mesh in AI over a still that simulates a mesh render from a 3d program of the body. You comp that with alpha on top of your character, reveal it with a feathered mask and then use another animated mask to wipe it off. The same mask should be copied on the top layer that should have the character (shoot both instances on chroma) dressed in the desired final outfit shot in the exact same position. The edge of this mask should animate smoothly to give a more organic look. Animate a shape (white) to match the edge of transition. Apply Generate/Cell Pattern, CC Light Rays, Colorama…. and instead of spending a lot of time writing this I have attached a project for the edge transition using only AE plugins that come with CS4.
2199_powerrangersmorphedgetransition.aep.zip
Tudor “Ted” Jelescu
Senior VFX Artist