Anti-aliasing method for polynomial curves using integer arithmetics

• US 5,479,590 A
• Filed: 09/07/1994
• Issued: 12/26/1995
• Est. Priority Date: 12/24/1991
• Status: Expired due to Term

• Current Assignee: PMC-Sierra Incorporated (Microchip Technology Incorporated)
• Original Assignee: Sierra Semiconductor Corp. (Microchip Technology Incorporated)
• Inventors: Lin, Tao
• Primary Examiner(s): Jankus, Almis R.
• Application Number:
  US08/302,041
• Time in Patent Office: 475 Days
• Field of Search: 395/150, 395/151, 395/140-143, 395/425, 395/126, 395/127, 395/128, 395/129, 395/131, 395/132, 345/136, 345/137, 345/138, 345/147, 358/525
• US Class Current: 345/611
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves

Abstract

A method of performing anti-aliasing on polynomial curves using only integer arithmetic. The anti-aliasing method includes the steps of: defining an polynomial equation of a curve, dividing grid units into an finite number of sub-intervals, associating a mix ratio to each of the sub-intervals, determining which sub-interval the curve bisects, assigning a mix ratio to each picture element bordering the grid unit according to the mix ratio associated with the sub-interval determined to be bisected by the curve.

Claims

1. A computer graphics rendering process for displaying on a raster scan computer display having a limited resolution of H×

V pixels an analytical curve that passes between centers of a pair of adjacent pixels in display space without intersecting the center of either pixel, the analytical curve to be displayed in a first shade or color on a background field displayed in one or more other shades or colors, comprising the steps of;

selecting a plurality of equidistant points along a line segment joining said adjacent pixels, said plurality of equidistant points including end points, defined by said adjacent pixels, of said line segment;

evaluating an analytic expression, defining said analytic curve, at a plurality of said equidistant points;

identifying, from among N ordinal pairs of adjacent ones of said plurality of equidistant points, an Mth pair between which said analytic curve passes;

assigning to each of said adjacent pixels, in accordance with the ratio M/N+1, a display shade or color that is a ratiometric combination of said first shade or color and another shade or color and that is different from both said first shade or color and said another shade or color;

displaying said adjacent pixels in their respective assigned shades or colors; and

repeating the foregoing steps for multiple such pairs of adjacent pixels.

2. The method of claim 1, wherein said evaluating step involves only integer arithmetic.

3. The method of claim 2, wherein said assigning step comprises:

for each of a plurality of color components, separately determining a ratiometric combination of a particular color component of said first color and a same particular color component of said another color.

4. The method of claim 2, wherein colors are represented in a single word format, and wherein said assigning step comprises:

simultaneously determining a ratiometric combination of said first color and said another color with respect to a plurality of color components.