Reciprocal generator using piece-wise-linear segments of varying width with floating-point format
US6260054A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 29, 1998 |
| Grant date | Jul 10, 2001 |
| Priority date | — |
| Expiry date | Oct 29, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2101/12
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A reciprocal generator is useful for perspective correction for 3D graphics. The input range is divided into many sections. A lookup table contains reciprocal outputs for only two of the sections, the smallest-inputs section and the largest-inputs section. Entries in the table for the smallest section contain a base and a scale factor to indicate the reciprocal value. One entry is provided for each possible input value in the smallest section. This provides high precision where the outputs have the largest values, reducing visible distortions caused by relatively small changes in the large output values. Each section is divided into intervals, with one table entry for each interval. For the largest section, each table entry has an initial reciprocal and a slope of a line approximating the reciprocal curve in that interval. Reciprocals for inputs within the interval are calculated by multiplying an offset into the interval by the slope, and then adding to the initial reciprocal for that interval. Each section is twice as wide as the previous section, but has the same number of intervals. A scale factor is generated by counting a number of leading zeros in the input. Then the input i…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.