The Lens of Truth (Zelda)
Not sure if I posted this here of not, I made a test file for the LoZ OOT Lens of truth
http://www.pasteall.org/blend/40248this is the file, the upload is only good for another few months, if you need it refreshed just ask.
open the file in blender 2.49b, you will need to have python 2.6.2 installed and blender must be able to find it.
once open press P to play.
arrow keys for movement, and press the
C button to activate the lens.
the trick is accomplished by having 2 "skyboxes" separating 2 versions of the "world", one with the "lies" and one with only the "truth". in the Truth skybox the camera has a transparent textured plane in front of it with the purple/violet circle outline which keeps things outside of the circle from being rendered. In the "lies" skybox, the camera has a plane that it can move in-front of the camera which uses a python script to make a texture rendered from the truth skybox's camera, the image rendered is set to partially transparent so you can see the lies scene outside the circle and the truth inside of it.
it's not perfect, the lies and truth objects appear kinda ghostly, but it works.