EP0049360A1
Expired / Lapsed
EP
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Graphic output system
Assignee: International Business Machines Corp
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Filing: 1981-08-28
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Granted: —
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Expires: 2001-08-28
Abstract
Abstract A graphic output system generates circular arcs of lengths up to and including a full circle of 360 degrees. Nonsymmetrical closest points are located for noninteger radius and arc center values. Incremental move commands are generated for drawing an arc either in the clockwise or counter clockwise direction which is a distinct advantage when used to drive a pen type electromechanical plotter. By dividing the generation of a 360 degree arc into eight octants, only two of the original eight directions need to be considered as candidate directions toward the next integer display matrix value to be displayed. Initialization provides a simple stopping test for any circular arc of arbitrary length and direction. Only simple addition and sign testing is used to display the circular arc.
Inventors
- 👤 Jack Elton Bresenham
- 👤 Donald George Grice
- 👤 Shing-Chou Pi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 22:13
CPC Classifications
G; G06; G06K; G06K15/00; G06K15/22; G09; G09G; G09G1/00; G09G1/06; G09G1/08; G09G1/10; G09G5/00; G09G5/20
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
125 words
A graphic output system for creating a portion of a circular arc on an incremental Cartesian coordinate output device comprising: a computer for establishing initialization parameters from specifications of a circular arc supplied by a graphic application program; logic (503) for testing an octant transition count for a termination octant; logic (541, 543, 545) for testing for an end point in said termination octant; logic (507) for testing for an octant boundary; logic (523, 527, 533) to reinitialize at least some of said initial parameters at each octant boundary; logic (511, 513) for selecting a unit direction for an incremental output movement; logic (515, 517) for modifying at least some of said initial parameters; and output means (41) for moving in said selected unit direction.
Claim 2
Dependent Claim
125 words
A graphic output system for creating a portion of a circular arc on an incremental Cartesian coordinate output device comprising: a computer for establishing initialization parameters from specifications of a circular arc supplied by a graphic application program; logic (503) for testing an octant transition count for a termination octant; logic (541, 543, 545) for testing for an end point in said termination octant; logic (507) for testing for an octant boundary; logic (523, 527, 533) to reinitialize at least some of said initial parameters at each octant boundary; logic (511, 513) for selecting a unit direction for an incremental output movement; logic (515, 517) for modifying at least some of said initial parameters; and output means (41) for moving in said selected unit direction.
Claim 3
Dependent Claim
59 words
A graphic output system of Claim 1 wherein said logic for testing octant transition-count further comprises: logic for executing a single sign test; and wherein said logic for testing for an end point in said termination octant operates as a function of the direction of rotation and an initial parameter (VlT), whether the termination octant is odd or even.
Claim 4
Dependent Claim
40 words
The graphic output system of Claim 1 wherein said logic to reinitialize at least some of said initial parameters at each boundary crossing reinitialize unit direction vectors, (Ml, M2), loop variables, (Vl, V2, V3), and loop constants (Kl, K2, K3).
Claim 5
Dependent Claim
72 words
The graphic output system of Claim 3 wherein said logic for testing an octant boundary also detects octant boundaries which are additionally quadrant boundaries; and wherein said logic for reinitializing at least some of said initial parameters reinitializes one of said unit direction vectors (M2) when a quadrant boundary has been detected and reinitializes another of said'unit direction vectors (Ml) when an octant boundary which is not a quadrant boundary is detected.
Claim 6
Dependent Claim
115 words
The graphic output system of Claim 1 wherein said computer comprises logic steps for establishing initial parameters further comprising: calculating (Fig. 11B) a closest integer point (XsYs, XtYt) and an error measure (Fs, Ft) to each of a stopping point and a termination point specified by said application program; determining initial loop variables, initial loop constants, initial unit direction vectors, a starting absolute octant indicator (Ks), and a major/minor arc resolution indicator (V10) from said starting point, and said start error measure and rotation direction; determining termination variables and a termination absolute octant indicator (Kt) from said termination point; calculating said octant count difference (Kl) from said absolute octant indicators and said arc indicator (V10).
References Cited (Backward Citations)
GB1244659A
Cited
FR2373840A1
Cited
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