Method of comprehensive distortion correction for a computer image generation system
First Claim
1. In an image generating system of the type for converting digital data into a sequence of display frames of image data in projector space suitable for display on a video image system in viewer space, the image system forming a display by individually illuminating each of a plurality of color pixels, each of the frames of image data defining a plurality of faces and each of the frames being divided into a plurality of spans, including an electronic control means for converting the digital data, a method for correcting for geometric distortion and optical distortion comprising the steps of:
- (a) identifying data for a frame of display, the data defining face locations in viewer space, each of the faces associated with at least one span and being arranged in a descending order of priority;
(b) calculating transformation coefficients for mapping projector space span corners into viewer space;
(c) determining the highest priority face for each span;
(d) determining an area within a viewer space span covered by the highest priority face;
(e) computing pixel image data representative of the pixels within the projector space span covered by the face;
(f) repeating step (c) through step (f) until the last face is processed into pixel image data or until all areas of the spans are fully covered by faces; and
(g) transferring the pixel image data to the video image system.
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Abstract
A method for computer image generation producing simulated visual scenes for applications such as flight training, employing a comprehensive distortion correction to generate the image takes place in three sequential stages: Controller, Geometry Processor, and Display Processor. The Display Processor generates video to produce the desired scene on the raster of the display device. If the scene is projected through a wide-angle lens and/or is projected onto a curved screen, the combination of optical and geometric distortion presents a highly distorted scene to the viewer. The comprehensive distortion correction method produces a precisely predistorted scene on the projector raster so it appears valid to the viewer. Mapping between projector space and viewer space is highly nonlinear. However, a small region of the display (span) is selected sufficiently small so that the projector/viewer transformation may be considered linear. The Geometry Processor defines face edges in viewer space and maps edge vertices into projector space. In the Display Processor detection of spans intersected by a given face is done in viewer space using the mapped span corners and edge coefficients defined by the Geometry Processor. Edge to span corner distances are determined in viewer space. This produces a piecewise linear approximation to the curves which exact mapping would provide. The edges are continuous at span boundaries and have slope discontinuities so small as to be imperceptable. The resulting scene appears fully valid to the viewer, with all distortions corrected.
72 Citations
38 Claims
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1. In an image generating system of the type for converting digital data into a sequence of display frames of image data in projector space suitable for display on a video image system in viewer space, the image system forming a display by individually illuminating each of a plurality of color pixels, each of the frames of image data defining a plurality of faces and each of the frames being divided into a plurality of spans, including an electronic control means for converting the digital data, a method for correcting for geometric distortion and optical distortion comprising the steps of:
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(a) identifying data for a frame of display, the data defining face locations in viewer space, each of the faces associated with at least one span and being arranged in a descending order of priority; (b) calculating transformation coefficients for mapping projector space span corners into viewer space; (c) determining the highest priority face for each span; (d) determining an area within a viewer space span covered by the highest priority face; (e) computing pixel image data representative of the pixels within the projector space span covered by the face; (f) repeating step (c) through step (f) until the last face is processed into pixel image data or until all areas of the spans are fully covered by faces; and (g) transferring the pixel image data to the video image system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. In an image generating system of the type for converting digital data into a sequence of display frames of image data in projector space suitable for display on a video image system in viewer space, the image system forming a display by individually illuminating each of a plurality of color pixels, each of the frames of image data defining a plurality of faces and each of the frame being divided into a plurality of spans, including an electronic control means for converting the digital data, a method for correcting for geometric distortion and optical distortion comprising the steps of:
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(a) identifying data for a frame of display, the data defining face locations in viewer space, each of the faces associated with at least one span; (b) calculating transformation coefficients for mapping projector space span corners into viewer space; (c) determining a face to be processed for each span; (d) determining an area within a viewer space span covered by said face; (e) computing pixel image data representative of the pixels within the projector space span covered by said face; (f) repeating step (c) through step (f) until a last face is processed into pixel image data; and (g) transferring the pixel image data to the video image system. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38)
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36. The method of claim 36, further comprising the step of determining the accuracy of a subpixel area assigned to the face by a positioned accuracy of at least one subpixel.
Specification