Using ray-tracing techniques
Anibal Jose da Silva
Clear Lake City TX 77062-4206
"Researchers focus ray-tracing techniques on contact-lens design," (Vision Systems Design, August 1997, p. 16) brought to mind a problem we encountered in visual simulation designed to provide wide fields of view to astronauts in training for the Approach and Landing Test Program at the onset of the Shuttle program. Our intent was to provide each of the Orbiter Aeroflight Simulator forward, quarter, and side windows with realistic televised color scenes during approach and landing training toward a color model of Edwards AFB (a two-tower translational gantry carried the articulated viewing optics and cameras).
It was realized early on that a single lens could not meet the requirement to simultaneously provide proper external scenes through the six windows in the cockpit. So, a single wide-field-of-view lens was chosen to provide four windows with scenes as selected by the instructor: the views displayed on the color monitors were either the two forward and two quarter windows, the two forward and left quarter and side windows, or the two forward and right quarter and side windows.
The concept was to imagine the point of view as being that of an observer in the middle of a hemisphere with its axis facing forward or through either the left or right quarter window and that that same point represented the viewpoint of the lens. The problem was how to map the external scene properly at the focal plane of three cameras such that the scene was correctly mapped regardless of which sets of windows were active. To resolve the problem a specially drawn black and white pattern (shaped much like a bow tie) was viewed by the lens, and the appropriate electronic distortion was introduced to the monitors to properly distort the images so that they appeared proper to the viewer in control.
While it was a huge success, digital image generation, even in its primitive cartoonish stage, shortly replaced the camera/model system. The electro-optical camera system was dismantled and the model was destroyed without ceremony, much to the dismay of Joe Engle who wanted to keep the part of the Edwards model with the concrete runways.
