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Virtual Reality


Virtual Reality Air Combat SystemEidetics Corporation has been involved in the application of Virtual Reality to aircraft simulation since 1992. Through the US Air Force Research Labs Small Business Innovative Research program called Virtual Reality for Close-In-Combat and internal research and development, Eidetics has developed a state-of-the-art Virtual Reality Air Combat Simulator (ViRACS). This system was delivered to Wright Patterson Air Force Base in April 1997.



In all simulation of manned vehicles, high quality visual feedback to the pilot is one of the most important elements required to provide full immersion in the training environment. In air combat simulation the visual display is particularly critical because a pilot's life depends upon what they can or cannot see. Moreover, pilots tend to have excellent vision, often better than 20/20. The visual system must provide high resolution and a wide field of regard. The importance of the visual system for aircraft simulation, as a result, has fostered several new technologies:

  • Real Time photo realistic, textured, graphics

  • Head tracking devices

  • Eye tracking devices

  • Domes

  • Head Slaved projectors

  • Virtual reality displays

  • Retinal displays

In the past, the preferred presentation of 360 field-of-view computer generated imagery has been a dome system. Domes come in many shapes and sizes. There are spherical domes and regular polyhedral based systems. There are domes with external projectors, internal projectors, and combinations thereof. Never the less, all domes share the feature that the display surface is independent of the users head position.


The major limitation of a dome system is the cost of providing sufficient display resolution over the entire dome. The cost of covering a dome with high resolution (eye limited) images can be reduced by utilizing area-of-interest projectors. In this arrangement a low resolution background image is projected over the whole dome and a high resolution inset is projected where the pilot is looking by tracking either the head or eye position. This approach remains cost effective as long as the cost of a slaved projector is less than the cost of additional image generators and fixed projectors.


Head Mounted Displays

Another approach that has become practical, is providing a 360 field of view in a head-mounted display. In the typical HMD configuration, the display is attached to the viewer's head so that he sees computer imagery no matter where he looks. The field of view of an HMD is typically quoted as the instantaneous field of view, since the total field of view is limited only by the users' head motion. A head tracker, typically mechanical or magnetic, is used to determine the correct eye point and orientation to draw the imagery in the HMD. Head-mounted systems therefore have the advantage of an area of interest projector, since they only provide high resolution imagery where the viewer is looking, at a substantially lower price.

The inherent benefits of a head-mounted approach are that it does not require large facilities, and it will tend to have lower costs for computer generated imagery. The principle detriments of a head-mounted approach are size, weight and balance. However, given the historical trends in electronics toward miniaturization we can expect these features to improve rapidly over time. Work is already underway to draw imagery directly into the users' eyes, and perhaps further in the future, research is progressing toward being able to stimulate the optic nerves electrically. It may be many years before this technology becomes available and affordable, but systems that are available today do provide high resolution, wide field of view displays with weights on the order of 4 pounds which has proven to be quite useable.



Eidetics' Virtual Reality Air Combat Simulator (ViRACS) utilizes an n-Vision DataVisor 80 HMD and a Silicon Graphics InfiniteReality Image Generator. The DataVisor 80 provides a full color, high resolution (1280 x 1024 pixels), wide field-of-view (120 x 60 degrees) stereo display to the pilot. The DataVisor 80 represents a great leap forward in capability for HMDs at a reasonable price. A partially immersive environment has been selected where the pilot is able to utilize glass cockpit gages that project through a computer generated cockpit mask in the HMD. The mask position is updated with head position as measured by a magnetic head tracking unit.

ViRACS also includes a full sized, fiberglass cockpit shell with a high fidelity, hands on stick and throttle control set and glass cockpit instrumentation. This system also has a sound system and a HMD repeater monitor.


Eidetics' ViRACS station may be integrated into different aircraft environments as necessary. Currently, Wright Patterson is using their station with Boeing's MIL-AASPEM II combat analysis tool to provide the aircraft and avionics math modeling. Eidetics uses the ViRACS system in conjunction with the ARENA full aircraft simulator. ViRACS is designed with a clean interface so that it may be integrated with many different simulations.



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