EP0582815A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for drawing lines, curves, and points coincident with a surface
Assignee: International Business Machines Corp
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Filing: 1993-06-22
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Granted: —
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Expires: 2013-06-22
Abstract
Abstract A method, for execution by a graphics processing system (10), for rendering objects for display to a viewer upon a display (20) having a plurality of display pixels. The method includes the steps of, for a surface to be displayed having a surface marking coincident therewith, (a) moving the surface marking towards the viewer or, alternatively, moving the surface away from the viewer, by an amount that is function of a parameter (S) and also a scale factor (K) that expresses a relationship between viewer eye coordinate units and display pixel units. The parameter (S) determines a maximum slope for the surface, relative to a viewing plane, such that the step of moving will not cause a portion of the surface marking to be obscured by the surface. The step of moving includes a step of (b) applying a predetermined transformation T' e from a viewer eye coordinate system to a modified viewer eye coordinate system. The predetermined transformation T' e is selected as a function of whether a perspective projection or an orthographic projection of the surface and surface marking upon a viewing plane is performed. For the perspective projection, the transformation T' e is shown to also compensate for the movement of the second object towards the viewer.
Inventors
- 👤 John Emery Allain
- 👤 Bruce David Lucas
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-10 01:05
CPC Classifications
G; G06; G06T; G06T15/00; G06T15/10; G06T15/40; G06T15/405
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
149 words
A method for execution by a graphics processing system for rendering, for display to a viewer upon display means having a plurality of display pixels, a surface having a surface marking coincident therewith, comprising the steps of: moving the surface marking towards the viewer or, alternatively, moving the surface away from the viewer, by an amount that is function of a parameter (S) and also a scale factor (K) that expresses a relationship between viewer eye coordinate units and display pixel units, wherein the parameter (S) determines a maximum slope for the surface, relative to a viewing plane, such that the step of moving will not cause a portion of the surface marking to be obscured by the surface; and wherein the step of moving includes a step of applying a predetermined transformation (T' e ) from a viewer eye coordinate system to a modified viewer eye coordinate system.
Claim 2
Dependent Claim
254 words
Method as set forth in Claim 1 wherein the predetermined transformation T' e is selected as a function of whether a perspective projection or an orthographic projection of the surface and the surface marking upon a viewing plane is performed, wherein, for the orthographic projection, the scale factor K preferalby is given by wherein Sδ/2= S/2K , where δ is a distance in the viewer coordinate system that corresponds to a pixel error distance in the viewing plane in drawing the surface marking against the surface, wherein a modified viewer coordinate system z-axis distance value z' e is given in terms of an unmodified viewer coordinate system z-axis distance value z e as z' e = z e + Sδ/2 = z e + S/2K, and wherein the predetermined transformation T' e is given by and wherein for the perspective projection the scale factor K preferably is given by wherein Sδ/2= z e S/2K , where δ is a distance in the viewer coordinate system that corresponds to a pixel error distance, in the viewing plane, in drawing the surface marking against the surface, and where z e is a distance along an unmodified viewer coordinate system z-axis, wherein a modified viewer coordinate system z-axis distance value z' e is given in terms of the unmodified viewer coordinate system z-axis distance value z e as z' e = z e + Sδ/2= z e - z e S/2K = z e (1 - S/2K), and wherein the predetermined transformation T' e is given by
Claim 3
Independent Claim
256 words
A method for execution by a graphics processing system for rendering, for display to a viewer upon display means having a plurality of display pixels, a surface having a surface marking coincident therewith, the surface and the surface marking to be displayed with an orthographic projection upon a viewing plane, comprising the steps of: moving the surface marking towards the viewer or, alternatively, moving the surface away from the viewer, by an amount that is function of a parameter (S) and also a scale factor (K) that expresses a relationship between viewer eye coordinate units and display pixel units, wherein the parameter (S) determines a maximum slope for the surface, relative to a viewing plane, such that the step of moving will not cause a portion of the surface marking to be obscured by the surface; and wherein the step of moving includes a step of applying a predetermined transformation (T' e ) from a viewer eye coordinate system to a modified viewer eye coordinate system, wherein the scale factor K is given by wherein Sδ/2= S/2K , where δ is a distance in the viewer coordinate system that corresponds to a pixel error distance, in the viewing plane, in drawing the surface marking against the surface, wherein a modified viewer coordinate system z-axis distance value z' e is given in terms of an unmodified viewer coordinate system z-axis distance value z e as z' e = z e + Sδ/2 = z e + S/2K, and wherein the predetermined transformation T' e is given by
Claim 4
Independent Claim
259 words
A method for execution by a graphics processing system for rendering, for display to a viewer upon display means having a plurality of display pixels, a surface having a surface marking coincident therewith, the surface and the surface marking to be displayed with a perspective projection upon a viewing plane, comprising the steps of: moving the surface marking towards the viewer or, alternatively, moving the surface away from the viewer, by an amount that is function of a parameter (S) and also a scale factor (K) that expresses a relationship between viewer eye coordinate units and display pixel units, wherein the parameter (S) determines a maximum slope for the surface, relative to a viewing plane, such that the step of moving will not cause a portion of the surface marking to be obscured by the surface; and wherein the step of moving includes a step of applying a predetermined transformation (T' e ) from a viewer eye coordinate system to a modified viewer eye coordinate system, wherein the scale factor K is given by wherein a modified viewer coordinate system z-axis distance value z' e is given in terms of the unmodified viewer coordinate system z-axis distance value z e as z' e = z e + Sδ/2= z e - z e S/2K = z e (1 - S/2K), where δ is a distance in the viewer coordinate system that corresponds to a pixel error distance, in the viewing plane, in drawing the surface marking against the surface, and wherein the predetermined transformation T' e is given by
Claim 5
Dependent Claim
26 words
Method as set forth in Claim 2, wherein T' e compensates for the movement of the surface marking or the surface with respect to the viewer.
Claim 6
Dependent Claim
73 words
Method as set forth in Claim 1, 2, 3, 4 or 5, wherein the transformation T' e is employed with a set of transformations that transform from object coordinates, to world coordinates (T w ), to eye coordinates (T e ), to screen coordinates (T s ) in accordance with: [wx s wy s wz s w] = [x o y o z o 1]T w T e T' e T s .
Claim 7
Dependent Claim
49 words
Method of Claim 1 or one of the claims 2 to 6, wherein (S) = |Δz/Δx| , or wherein (S) = |Δz/Δy| , or wherein (S) equals a combination of |Δz/Δx| and |Δz/Δy| in an (x, y, z) viewer coordinate system, and/or wherein (S) is equal to approximately eight.
Claim 8
Dependent Claim
182 words
A graphics processing system including display means having a plurality of display pixels for displaying a representation of a surface having a surface marking coincident therewith, said graphics processing system comprising: means for moving the surface marking towards the viewer or, alternatively, moving the surface away from the viewer, by an amount that is function of a parameter (S) and also a scale factor (K) that expresses a relationship between viewer eye coordinate units and display means pixel units, wherein the parameter (S) determines a maximum slope for the surface, relative to a viewing plane of the display means, such that the operation of the moving means does not cause a portion of the surface marking to be obscured by the surface; and wherein the moving means includes means for applying a predetermined transformation (T' e ) from a viewer eye coordinate system to a modified viewer eye coordinate system, the predetermined transformation T' e being selected as a function of whether a perspective projection or an orthographic projection of the surface and the surface marking upon a viewing plane is performed.
Claim 9
Dependent Claim
73 words
A graphics processing system as set forth in Claim 8, wherein the applying means applies the transformation T' e with a set of transformations that transform from object coordinates, to world coordinates (T w ), to eye coordinates (T e ), to screen coordinates (T s ) in accordance with: [wx s wy s wz s w] = [x o y o z o 1]T w T e T' e T s .
Claim 10
Dependent Claim
49 words
A graphics processing system as set forth in Claim 8 or 9, wherein (S) = |Δz/Δx| , or wherein (S) = |Δz/Δy| , or wherein (S) equals a combination of |Δz/Δx| and |Δz/Δy| in an (x, y, z) viewer coordinate system, and/or wherein (S) is equal to approximately eight.
References Cited (Backward Citations)
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