Playing with light.

From Adam Frank - the company behind Lumen - two projects:

Shadow
Shadow is an interactive installation that projects a disembodied, autonomous, human shadow on the ground. This apparently living shadow attempts to merge itself with the viewer's real shadow. When this occurs, the invisible figure, implied by the virtual shadow, inhabits the viewer's own personal space. Real-time 3D graphics and video sensing are used to produce this work of interactive light.

Sunray
A proposal for Grand Central Station NYC – Sunray projects an animated sun on the ceiling of Grand Central Station. The sun appears to rise over the east side of the Main Concourse and set in the west. At certain times of day, it appears as if the roof is invisible. Viewers have the momentary sensation of seeing the real sun.