Examples of illusory rigid planar patches arise directly from projective coordinate transformations applied to individual images, allowing messages to be left on everyday planar textures in the real world, visible to those wearing the eyeglasses, and on the list of recipients for a particular message (Fig 3).
Figure 3: Message left on the flat wall of department store entrance remains dormant until recipient of message happens to look at wall. The act of looking, being mediated by the apparatus, enables the message to appear as an illusory planar patch. (Thanks to Jeffrey Levine for help with work in this figure.)
Face recognition has been used together with `video orbits' to create existential name tags (e.g. don't exist in reality but can be seen by wearer of apparatus) where the name had been entered at a previous encounter or drawn from a database.