Invalidity dossier
US 5125073
Method and apparatus for adaptive forward differencing in the rendering of curves and surfaces
Current assignee: Sun Microsystems Inc
Added 9/23/2026, 12:51:43 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US5125073A
Title: Method and apparatus for adaptive forward differencing in the rendering of curves and surfaces
Patent number: US5125073A
Application number: US07/433,430
Inventors: Sheue-Ling Lien, Michael J. Shantz, Serdar Ergene, Vaughan R. Pratt, Jerald R. Evans
Assignee: Sun Microsystems Inc. (original and current assignee per the listing)
Priority date: 1987-05-08
Filing date: 1989-11-08
Publication/grant date: 1992-06-23
Status listed: Expired – Fee Related; anticipated expiration 2009-06-23
Purpose: The invention relates to generating images on a CRT or other display device, specifically to accurate rendering of higher-order curves and curved surfaces. Rather than subdividing curves into many straight-line or planar polygon approximations, it uses adaptive forward differencing (AFD) to advance along a parametric curve or surface in steps sized to about one pixel increment.
Plain-language scope: The apparatus receives data points defining an image and incrementally renders the curve in substantially uniform single-pixel steps. It includes X, Y, Z, and W Adaptive Forward Differencing Unit (AFDU) circuits computing homogeneous coordinates; the W output feeds a 1/w circuit whose reciprocal is multiplied by x, y, and z to yield rational cubics x/w, y/w, z/w. A pixel filter compares the current pixel location with the previous one and instructs the AFDU circuits to increase or decrease the step size (adjust up by multiplying parameter t by two, or adjust down by dividing by two), or to step forward, keeping advancement to roughly single-pixel increments. The pixel filter also detects and replaces "elbows" (corner pixels). The AFDU circuit reportedly implements the Bresenham algorithm using shared components. The description also mentions means for clipping regions, mapping imagery onto curves and surfaces, and shading/trimming surfaces, plus an arc-length output used for textured lines (expressly not an essential part of the invention as claimed).
Classification: G06T11/23; G09G5/20.
What the excerpt does not establish: It does not include the actual claims, the full specification, drawings, or cited prior-art references, so the precise legal scope of coverage cannot be determined from it. It also does not establish litigation, ownership transfers, validity, or the accuracy of the listed legal status.
Source: https://patents.google.com/patent/[US5125073](/patent/US5125073)/en
Generated 10/1/2026, 9:53:26 PM
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Assignment history
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Prior art
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