Patent
1995-04-13
1997-02-18
Jankus, Almis R.
395133, G06T 1100
Patent
active
056048521
ABSTRACT:
A graphics controller for use in a computer system includes a run slice line draw engine to generate a line as a plurality of slices. The run slice line draw engine calculates the length of the slices responsive to line definition parameters, such as the coordinates of the two line endpoints. Groups of like-sized slices can be determined to decrease the computations necessary to compute the size of each slice. The slices can be either drawn to the display through the frame buffer or used as endpoints for other lines to be generated. To increase the speed of operation, while parameters requiring a division are being calculated, the partial quotient is being used to generate partial slices. Clipped lines can be generated in part using normal Bresenham techniques for partial slices and using the run slice techniques for the full slices entirely within a window. The run slice line draw engine can be used for a plurality of functions other than simple line draws, such as polygon fills, stretching, shrinking or shading. Non-linear scaling and nonlinear shading can be performed in accordance with a parametric equation by approximating the parametric equation as a polyline having a plurality of linear segments. Scaling and/or shading can be performed responsive to the linear segments of the polyline, thereby avoiding complex mathematical computation. A polyline approximating a parametric equation of degree n may also be displayed on a video display using information generated for n-1 derivatives of the parametric equation.
REFERENCES:
patent: 5444825 (1995-08-01), Bain et al.
IBM Technical Disclosure Bulletin, vol. 21, No. 5, Oct. 1978, pp. 2041-2044.
IBM Technical Disclosure Bulletin, vol. 22, No. 8B, Jan. 1980, pp. 3744-3747.
IBM Technical Disclosure Bulletin, Vo. 18, No. 4, Sep. 1975, pp. 1075-1077.
Dao Giang H.
Spurlock Randolph W.
Watters John J.
Compaq Computer Corporation
Jankus Almis R.
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