In a curved screen setup the projectors are tuned to display in one of two ways to account for the curvature of the screen. One mode is sometimes called "Real World" mode, but in this document the term "Fixed Projection Point" (FPP) mode is used because we feel it is more descriptive of the setup. The other mode the projectors can be configured for is called "SuperDesktop" (SD) mode, or sometimes called "MegaDesktop" mode. Each of these projection modes has its pros and cons. This document will discuss each of these modes in detail, as well as discuss how the type of projection mode that is being used will influence the configuration of the display pipes and channels, the CAVELib application, as well as tracking.
The configuration of curved screen display systems always seems to be a somewhat confusing task. The main reasons for this is because there are two different display modes in which these systems can be configured in, the display has non-planar screens, and the projected images have overlapping blended regions. The FPP mode and the SuperDesktop mode each require the projectors to output an image in a format that is different than the other mode. These two projection modes each have their pros and cons, and they also affect the type of interactions that are then allowable by the display software. One mode, FPP, can provide a perfect perspective projection, but only for a fixed viewpoint, which eliminates the ability to do head tracking. The other mode, SuperDesktop, allows a tracked head perspective but only for an approximated projection plane that results in various visual anomalies.
For a complete white paper on the issues with curved screen displays please email support@vrco.com and ask for the Curved Screen White Paper. The remainder of this chapter covers curved screen configurations in a very abbreviated way. Anyone wishing for more information should contact VRCO.
Curved screens can be run monoscopically or in stereo, but frequently with no tracking; users are seated, and typically interact using a flybox, a mouse and keyboard, or other typical desktop interfaces. But this is not say that some setups aren't run with head tracking. But the draw back to a curved screen is that head tracking can only be done with approximated view planes resulting in visual anomolies (fish-eyed views at the edges of the screen).