US3816726A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Computer graphics clipping system for polygons
Assignee: Evans and Sutherland Computer Corp
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Filing: 1972-10-16
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Granted: 1974-06-11
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Expires: 1992-10-16
Abstract
Abstract A system is disclosed for clipping three-dimensional polygons for use in a computer-graphics display. The system removes from each polygon all parts that lie outside an arbitrary, planefaced, convex polyhedron, e.g. a truncated pyramid defining a viewing volume. The polygon is defined by data representing a group of vertices and is clipped separately in its entirety against each clipping plane (of the polyhedron). In a multiplestage structure as disclosed, each stage clips the polygon against a single plane and requires storage for only two vertex values. A time-sharing embodiment of the system is also disclosed. The disclosed system also incorporates the use of a perspective transformation matrix which provides for arbitrary field-of-view angles and depth-of-field distances while utilizing simple, fixed clipping planes.
Inventors
- 👤 I Sutherland
- 👤 G Hodgman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:39
CPC Classifications
G; G06; G06T; G06T15/00; G06T15/10; G06T15/40; G06T15/405; G09; G09G; G09G1/00; G09G1/06
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
51 words
A clipping method for defining select data, as for a perspective display comprising the steps of: representing data in the form of electrical signals manifesting coordinate locations; defining a polyhedron for containing select data; testing said electrical signals to generate those signals defining data within sAid polyhedron as said select data.
Claim 2
Dependent Claim
51 words
A clipping method for defining select data, as for a perspective display comprising the steps of: representing data in the form of electrical signals manifesting coordinate locations; defining a polyhedron for containing select data; testing said electrical signals to generate those signals defining data within sAid polyhedron as said select data.
Claim 3
Dependent Claim
19 words
A clipping method according to claim 1 wherein said electrical signals represent vertices in three-dimensional space by four-dimensional coordinates.
Claim 4
Dependent Claim
31 words
A method according to claim 1 wherein said electrical signals represent vertex locations defining a polygon, whereby said select data defines the portion of said polygon that lies within said polyhedron.
Claim 5
Dependent Claim
24 words
A method according to claim 3 wherein said testing step includes testing said vertex locations in relation to sides of said polyhedron in sequence.
Claim 6
Dependent Claim
35 words
A clipping method according to claim 3 wherein said testing step includes a step of computing data representative of intersections between represented data and a plane of said polyhedron to thereby define other vertex locations.
Claim 7
Dependent Claim
14 words
A method according to claim 3 wherein said polyhedron comprises a pyramidal vision projection.
Claim 8
Dependent Claim
11 words
A method according to claim 6 wherein said pyramid is truncated.
Claim 9
Dependent Claim
26 words
A method according to claim 6 wherein said testing step includes testing said vertex locations sequentially in relation to each side of said pyramidal vision projection.
Claim 10
Dependent Claim
27 words
A system according to claim 6 further including a preliminary step of processing said electrical signals to produce matrix-multiplied signals whereby to translate said pyramidal vision projection.
Claim 11
Dependent Claim
97 words
A clipping method for processing data that is representative of a polygon and is manifest by electrical signals specifying vertex locations of such polygon, comprising the steps of: defining a pyramidal field of vision by at least four defined surfaces; testing said electrical signals representing said vertex locations in relation to said defined surfaces to identify selected vertex locations as are within said field of vision; determining intersection locations of said polygon with said pyramidal field of vision to define a portion of said polygon within said field of vision in combination with said selected vertex locations.
Claim 12
Dependent Claim
97 words
A clipping method for processing data that is representative of a polygon and is manifest by electrical signals specifying vertex locations of such polygon, comprising the steps of: defining a pyramidal field of vision by at least four defined surfaces; testing said electrical signals representing said vertex locations in relation to said defined surfaces to identify selected vertex locations as are within said field of vision; determining intersection locations of said polygon with said pyramidal field of vision to define a portion of said polygon within said field of vision in combination with said selected vertex locations.
Claim 13
Independent Claim
116 words
A system for clipping a polygon comprising: means for providing vertex electrical signals representative of vertex locations specifying said polygon; means for registering a pyramidal projection figure including a plurality of planes; means for receiving said electrical signals representative of vertex locations, and coupled to said means for registering, to identify certain of said vertex electrical signals as representative of vertex locations internal of said figure; and means for receiving said electrical signals representative of vertex locations, and coupled to said means for registering, to provide intersection electrical signals representative of intersections between said polygon and said figure to specify, in combination with said certain vertex electrical signals, the portion of said polygon within said figure.
Claim 14
Independent Claim
116 words
A system for clipping a polygon comprising: means for providing vertex electrical signals representative of vertex locations specifying said polygon; means for registering a pyramidal projection figure including a plurality of planes; means for receiving said electrical signals representative of vertex locations, and coupled to said means for registering, to identify certain of said vertex electrical signals as representative of vertex locations internal of said figure; and means for receiving said electrical signals representative of vertex locations, and coupled to said means for registering, to provide intersection electrical signals representative of intersections between said polygon and said figure to specify, in combination with said certain vertex electrical signals, the portion of said polygon within said figure.
Claim 15
Dependent Claim
29 words
A system according to claim 11 wherein said means for providing vertex electrical signals comprises means for providing signals representative of homogeneous coordinates to define vertices in three-dimensional space.
Claim 16
Dependent Claim
28 words
A system according to claim 12 further including a matrix multiplier for acting on said vertex electrical signals for translating said signals in relation to said pyramidal projection.
Claim 17
Dependent Claim
27 words
A system according to claim 11 wherein said means for registering a figure includes means for registering data to specify six planes definitive of a truncated pyramid.
Claim 18
Dependent Claim
30 words
A system according to claim 11 wherein said means for registering a figure includes means for registering data to specify a plurality of planes definitive of a field of vision.
Claim 19
Dependent Claim
49 words
A system according to claim 15 wherein said means for providing vertex electrical signals provides coordinate signals representative of coordinate values dimensionally related to said planes definitive of said field of vision and wherein said means for identifying includes means for identifying vertex signals in relation to said planes.
Claim 20
Dependent Claim
42 words
A system according to claim 16 wherein said means for identifYing vertex signals in relation to said planes includes a plurality of registers for said vertex signals and means for sequentially testing said coordinate signals in relation to each of said planes.
Claim 21
Dependent Claim
30 words
A system according to claim 17 wherein said means for sequentially testing includes an arithmetic unit and means for time sharing said unit in relation to said plurality of registers.
Claim 22
Dependent Claim
19 words
A system according to claim 17 wherein said means for sequentially testing includes a plurality of individual processing units.
References Cited (Backward Citations)
US3602702A
Cited
US3639736A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-10 | 1977-12-10 | 1978-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-10 | 1981-12-10 | 1982-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-10 | 1985-12-10 | 1986-06-11 | $7700.00 | Window Closed / Lapsed |