http://projects.star.t.u-tokyo.ac.jp...DIA/xv/oc.html
What is Optical Camouflage?
Optical camouflage is a kind of active camouflage.
This idea is very simple. If you project background image onto the masked object, you can observe the masked object just as if it were virtually transparent.
This shows the principle of the optical camouflage using X'tal Vision. You can select camouflaged object to cover with retroreflector. Moreover, to project a stereoscopic image, the observer looks at the masking object more transparent.
Optical camouflage can be applied for a real scene. In the case of a real scene, a photograph of the scene is taken from the operatorfs viewpoint, and this photograph is projected to exactly the same place as the original. Actually, applying HMP-based optical camouflage to a real scene requires image-based rendering techniques.