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# Elimination of Staircasing in a Raster Display

IP.com Disclosure Number: IPCOM000085135D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 40K

IBM

## Related People

Bantz, DF: AUTHOR

## Abstract

An apparatus is described for minimizing the visual impact of "staircasing" in the display of digitally generated vectors on a raster or matrix-addressed display device, by adding a second matrix display point on the opposite side of the theoretical vector and modulating both spots as a function of their respective displacements from the theoretical line.

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Elimination of Staircasing in a Raster Display

An apparatus is described for minimizing the visual impact of "staircasing" in the display of digitally generated vectors on a raster or matrix-addressed display device, by adding a second matrix display point on the opposite side of the theoretical vector and modulating both spots as a function of their respective displacements from the theoretical line.

Necessarily any raster or matrix display must choose a display element in the matrix which occupies a position closest to the ideal vector. Except for vectors disposed at 0 degrees, 45 degrees, or 90 degrees with respect to the display axes, this will yield a succession of steps.

Referring to Fig. 1, which depicts the trace of the ideal vector 10 having a slope Delta Y/ Delta X of 5/2, it will readily be appreciated that only at X=0,Y-0 and X=2,Y=5 can the display register be set with coordinates that fall on the ideal vector. At the intermediate points in the display, the nearest display element must be chosen. This will result in the "staircase" effect. Points 1, 2, 4, 5, 7, and 8 are chosen as the elements in the display lying closest to the ideal vector 10.

Normally all points in the display are equally illuminated. If now a second point is added to the display and all points (including the added points) are modulated in intensity in accordance with their displacement from the ideal vector, the additional points 3 and 6 (shown as open circles) will appear.

The intensity is modulated in accordance with the relationship I = 1-0.25D, wherein D is the displacement from the theoretical. The points 4a and 5a (shown as dotted squares) will not appear in the display, because the stepping rules prohibit stepping both X and Y simultaneously.

The respective intensities of each of the display points are as shown in Fig. 1.

The apparatus for achieving the display effect shown graphically in Fig. 1 is shown in Fi...