Footprint or breadcrumb animation
A simple way in blender or any other 3d package would be to use a boolean modifier, if you want to subtract real geometry:




use a array modifier to duplicate your shape
create a path and aligning the objects on it
animate the object count of the array modifier
create a simple geometry for subtracting the path objects at the beginning
add a boolean modifier to your base object
animate the position of the boolean object to subtract the shape objects
make the boolean object invisible to the camera (e.g. with a transparent material)




.blend file



Edit: To get a soft transition you can render the bool object seperatly, blur the alpha channel and subract it from the another alpha. Or simply use a roto mask. 





.blend