Method and apparatus for performing polygon fills in graphical applications
US4897805A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 17, 1988 |
| Grant date | Jan 30, 1990 |
| Priority date | — |
| Expiry date | May 17, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T11/40
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method of filling a polygon as represented on a scan-line raster display includes storing data representative of the polygon edges, computing the points of intersection of a scan-line with each polygon edge, assigning a count having a parity value to each crossed-edge, and combining all colinear horizontal edges at the points of intersection. The number of polygon edges positioned above the colinear horizontal edge and which have a vertex coincident with the colinear horizontal edge, as well as the number of polygon edges positioned below the colinear horizontal edge and which have a vertex coincident with the colinear horizontal edge, are calculated. The parity of the crossed-edge count is inverted if the parity of both the above edge count and below edge count are even, and the string of pixels along the raster display scan-line from the current edge intersection to the next edge intersection are modified if the parity of the crossed-edge count is odd.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.