General Electric Company

Edward M Sims

Walter R Steiner

Richard Economy

Jimmy E Chandler

Gregory C Buchner

Lee T Quick

William A Kelly

Michael L Morgan

Michael W Tackaberry

Edwin O Howard

A method for distortion correction of computer-generated textured images maps vertices and texture coefficients from viewer space to projector space, so that environmental objects are pre-distorted upon the projection raster in order to appear in their proper form and perspective when the raster is projected onto a curved surface in viewer space, and viewed therefrom. Distortion correction is carried out by utilizing a piecewise-linear approximation for smoothly, continuously and closely approximating the required pre-curvature. The viewing space raster is subdivided into a number of triangles, within each of which a linear approximation is applied to the image mapping: the raster faces are first subdivided along the lines of a rectangular grid and the face fragments falling within each rectangle are then subdivided along the grid diagonal. This produces face fragments which are small enough so that a linear approximation provides an accurate transformation of each fragment. Distortion maps, typically computed off-line and stored in a database memory, are utilized to project the edges and texture modulation gradients from view space back into projector space, so that the edges and texture patterns can now be matched at intersections of adjacent triangles, in a manner to be substantially devoid of any abrupt changes, and thus be properly pre-distorted.

Polygon fragmentation method of distortion correction in computer image

The values of an attribute, like color, to be assigned to the right and left half of a pixel of a display device, such as may be determined by a computer image generation system, are compared for determining a difference value. If the difference value is less than a predetermined threshold, an average of the left and right half values is assigned to the pixel. If the difference value is greater than or equal to the threshold, then the right and left half values are assigned to the respective right and left halves of the pixel and during the raster scan, the attribute value of the pixel to be displayed is transitioned at the beginning of the pixel interval and in the middle of the pixel interval so that the pixel presents an image in response to the corresponding right and left half values. The data for the left and right half values may be truncated and stored as a portion of the data word or may be encoded into logarithmetic form having a mantissa and shift code. In either case, the data word may be the same length as words previously used to define the color of a pixel, thereby avoiding having to alter memory allocation of existing systems.

Picture element encoding

A low cost, true-perspective texture/shading processor (16) for a raster graphics display is based on a mathematical model which defines modulations globally over the entire simulated, visual environment. The model uses planes defined in three-dimensional space to define the modulation. These texture planes are all orthogonal to a single gradient in a flat reference plane and cut across any number of faces. The texture/shading processor is used in a computer image generator of the type wherein a first group (11) manages a visual data base (10) and transfers data to the active environment storage of a second group (12). The second group reduces the three-dimensional description of the environment supplied by the first group to a two-dimensional description, makes perspective transformation of data into coordinates of a view window and assigns a priority to each surface of the computed scene. A third group reduces the two-dimensional description generated by the second group to a scan line by generating edge data (14) to locate where edges cross the scan line and responds to the assigned priorities (15) to eliminate hidden surfaces and generates the video for display ( 17) including edge smoothing, shading and texture effects. The second group further includes a face modulation processor (13) for computing data describing each texture and shading model and data describing the plane of each textured or shaded face. The texture/shading processor (16) is in the third group and is responsive to initialization data from the first group and the data computed by the face modulation processor for computing texture and shading modulation signals.

True-perspective texture/shading processor

Growing community of inventors

Ormond Beach, FL, United States of America

Edward M Sims