Shadows and video projection

Creating fake shadows with video projection is quite easy and very nice.
I'd like to create some illusions mixing real and fake shadows : adding or removing shadows to objects and people. I've already been working on it a while ago :
https://vimeo.com/73462227 (zepetra)
Another video from the guy I worked with : https://www.youtube.com/watch?v=O8yaoDuq55I&feature=youtu.be

This another (bad) example of fake shadows : https://vimeo.com/14219338
In my opinion the idea is good but the realisation is bad, it should be much smoother, and using cubes is not very poetics. A better approach, from friends of mine : https://www.youtube.com/watch?v=X2VOxGSFbrM

?? Could we blend these digital shadows (coming from filmed visitors' body) to analogical ones generated with lights and visitors' body??

The ones made analogically can be made with some flash lights (manipulated by the visitors themselves), or with spot lights located in specific places around the "playground", (if these spot lights could move, it would be even better in order to disturb the angles and the space), or with directly beamer, this way we can directly generated video feedback from the shadows as well.

We need powerful beamers anyway to stand the stream of lights and a nice and total darkness..