Patent US5012433A successfully refreshed from Google Patents.
US5012433A
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Multistage clipping method
Assignee: International Business Machines Corp
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Filing: 1989-06-09
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Granted: 1991-04-30
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Expires: 2009-06-09
Abstract
Abstract A method for clipping two and three dimensional graphic primitives for use in a computer graphics workstation. During the first clipping stage, the system removes all graphic primitives which lie outside an arbitrary clipping volume or window that is an enlargement of the desired viewing volume or window. This clipping volume (window) is then projected and mapped onto a virtual viewport which is larger than the real viewport. After this mapping occurs, rendering effects (such as line styles, line width, pattern fill, hatch fill, etc.) are applied to the primitive. A subsequent stage of clipping is then applied to clip the virtual viewport to the real viewport which is the user's visible area. Use of the clipping volume (window) during the first stage of clipping makes it simpler to transform geometric primitives which are partially visible to the viewer, and gives visible primitives a richer set of invariant geometric properties so that their rendering effects may be more easily and correctly carried out.
Inventors
- 👤 Robert M. Callahan
- 👤 Bruce C. Hempel
- 👤 Bob C. Liang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 12:23
CPC Classifications
G; G06; G06T; G06T15/00; G06T15/10; G06T15/30
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
86 words
A method for performing clipping in a graphic workstation by a multistage technique, wherein said method operates on geometric data in said workstation, said data having size characteristics, said method comprising the steps of: establishing a first clipping region larger than a desired field of view; defining a virtual viewport which is a mapping transformation of said first clipping region, said virtual viewport being defined for accurately clipping geometric primitives; and selecting said first clipping region based on said size characteristics of the data being processed.
Claim 2
Independent Claim
86 words
A method for performing clipping in a graphic workstation by a multistage technique, wherein said method operates on geometric data in said workstation, said data having size characteristics, said method comprising the steps of: establishing a first clipping region larger than a desired field of view; defining a virtual viewport which is a mapping transformation of said first clipping region, said virtual viewport being defined for accurately clipping geometric primitives; and selecting said first clipping region based on said size characteristics of the data being processed.
Claim 3
Dependent Claim
40 words
The method of claim 1, further comprising the steps of: first clipping said geometric data using said clipping region; mapping the clipped geometric data to said virtual viewport; and clipping said mapped geometric data to said desired field of view.
Claim 4
Dependent Claim
15 words
A method according to claim 1 in which said first clipping region is a volume.
Claim 5
Dependent Claim
15 words
A method according to claim 1 in which said first clipping region is a polyhedron.
Claim 6
Independent Claim
79 words
A method for generating pixel data for image display in a graphic display system including the steps of: generating geometric data in a world coordinate space; selecting a data subset containing geometric data to be displayed, whereby that part of the data outside a first clipping region is eliminated; mapping said selected data subset to a virtual viewport; eliminating that part of the virtual viewport outside a real viewport; and generating pixel data for the image to be displayed.
Claim 7
Independent Claim
79 words
A method for generating pixel data for image display in a graphic display system including the steps of: generating geometric data in a world coordinate space; selecting a data subset containing geometric data to be displayed, whereby that part of the data outside a first clipping region is eliminated; mapping said selected data subset to a virtual viewport; eliminating that part of the virtual viewport outside a real viewport; and generating pixel data for the image to be displayed.
Claim 8
Dependent Claim
66 words
A method for performing multistage clipping in a graphics workstation according to claim 5 in which a mapping transformation is applied from said first clipping region to said virtual viewport, said method comprising the further steps of: determining said virtual viewport as a function of said real viewport; and calculating said first clipping region by applying the inverse of said mapping transformation to said virtual viewport.
Claim 9
Dependent Claim
26 words
A method according to claim 6 in which said virtual viewport is selected as a function of the real viewport and the graphics primitive being processed.
Claim 10
Dependent Claim
15 words
A method according to claim 5 in which said first clipping region is a volume.
Claim 11
Dependent Claim
15 words
A method according to claim 5 in which said first clipping region is a polyhedron.
Claim 12
Independent Claim
80 words
A method for generating data for image display from a graphics primitive in a graphics display system, comprising the steps of: transforming said graphics primitive from a first to a second coordinate space; clipping said transformed graphics primitive against a first clipping region; mapping said clipped graphics primitive from said first clipping region to a virtual viewport; generating pixels from said mapped graphics primitive; and clipping those pixels generated from said mapped graphics primitive that are outside a real viewport.
Claim 13
Independent Claim
80 words
A method for generating data for image display from a graphics primitive in a graphics display system, comprising the steps of: transforming said graphics primitive from a first to a second coordinate space; clipping said transformed graphics primitive against a first clipping region; mapping said clipped graphics primitive from said first clipping region to a virtual viewport; generating pixels from said mapped graphics primitive; and clipping those pixels generated from said mapped graphics primitive that are outside a real viewport.
Claim 14
Dependent Claim
29 words
A method according to claim 10 wherein said first clipping region has dimensions that are related to dimensions of a viewing region by a function of said graphics primitive.
Claim 15
Dependent Claim
46 words
A method according to claim 10 in which said virtual viewport is selected as an enlargement of the real viewport such that if the mapped graphics primitive does not enter the virtual viewport, the pixels generated from said graphics primitive do not enter the real viewport.
Claim 16
Dependent Claim
47 words
A method according to claim 10 in which said virtual viewport is selected as the minimal enlargement of the real viewport such that if the mapped graphics primitive does not enter the virtual viewport, the pixels generated from said graphics primitive do not enter the real viewport.
Claim 17
Dependent Claim
15 words
A method according to claim 10 in which said first clipping region is a volume.
Claim 18
Dependent Claim
15 words
A method according to claim 10 in which said first clipping region is a polyhedron.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-29 | 1994-10-29 | 1995-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-29 | 1998-10-29 | 1999-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-29 | 2002-10-29 | 2003-04-30 | $7700.00 | Window Closed / Lapsed |