Rendering shaded areas with boundary-localized pseudo-random noise
US5179641A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1989 |
| Grant date | Jan 12, 1993 |
| Priority date | — |
| Expiry date | Jun 23, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G2320/0247
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A computer graphics technique for rendering shaded areas by using pseudo-random noise localized to image boundaries is disclosed. Calculated pixel values are initially generated using an arithmetic accuracy larger than the word size of an associated bitmap memory. The calculated pixel values thus have a most significant portion, corresponding to the portion which is to be stored in bitmap memory, and a least significant portion, corresponding to the additional accuracy. Pseudo-random noise, preferably generated by a linear feedback shift register, is then added to some or all of the least significant portion, and the carry output from this operation is added to the most significant portion. The most significant portion is then written into bitmap memory. Changes in the value of the integer portion thus occur with increased frequency as the distance to an intensity boundary decreases, since the random noise causes the dithering to occur with increased frequency. The result is a more natural display than would otherwise be available with a given bitmap memory word size.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.