Soft shadows trick

"A simple setup to get correct soft shadows from lights. It's based on the spinning light trick, but a bit elaborated. Motion blur is required; it works great with Fprime, and it's good for animation....
....It gives a good circular soft shadow, like sun's one or even interior lamps.
It can be improved with sliders; you can get custom-shape shadows modifying target's path.
Just load the scene, put an object on a plane and play with it, it's fairly simple and can be improved... place here your ideas if you like."