http://www.newscientist.com/blogs/nstv/2011/11/3d-rabbit-appears-on-screen-made-of-mist.html
They used fog to stop the light on an arbitary position. So it appears to us the picture is a 3D.
http://www.newscientist.com/article/mg20827923.000
Damn it, I was far behind.
http://singularityhub.com/2010/10/20/this-rocking-lead-singer-is-a-3d-hologram-video/
Whoa, did you believe that?