Specifying 3D reference points in 2D graphic displays

• US 5,129,054 A
• Filed: 03/12/1990
• Issued: 07/07/1992
• Est. Priority Date: 03/12/1990
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sherman, Stephen P., Lascelles, Martin C., Hicke, Jeffrey A., Alstad, John K., Wong, Michael
• Primary Examiner(s): Clark, David L.
• Application Number:
  US07/492,520
• Time in Patent Office: 848 Days
• Field of Search: 364/518, 364/521, 364/522, 364/146, 364/474.22, 340/706-710, 340/729, 395/119, 395/120, 395/122, 395/127, 395/155, 395/161
• US Class Current: 715/766
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 3/073 Transforming surfaces of revolution to planar images, e.g. cylindrical surfaces to planar images

Abstract

Correlation of two-dimensional displayed points of an axonometric projection with corresponding three-dimensional points of the projected shapes. A point on a display screen surface is selected and the screen coordinates of the points of the three-dimensional shape are found by converting successive points of the shape to two-dimensional screen equivalents. Comparing the converted coordinates to those of the selected point identifies the shape point corresponding to the selected shape.

Claims

1. In a graphics display system representing three-dimensional objects on a two-dimensional display screen, a method of selecting three-dimensional coordinates of a point of a three-dimensional object as a reference point for the execution of an operation relative to said three-dimensional object comprising the steps of:

selecting a reference point on the two-dimensional display screen corresponding to the reference point on a three-dimensional object on which said operation is to be performed;

determined the two-dimensional coordinates of the selected point relative to the display screen;

converting stored three-dimensional coordinates representing displayed points to two-dimensional coordinates relative to the display screen;

comparing the determined two-dimensional coordinates to the converted two-dimensional coordinates until an equality results; and

executing the operation on the three-dimensional object with respect to the reference point determined as the three-dimensional point having converted two-dimensional coordinates equal to the selected two-dimensional point.

2. The method claimed in claim 1 wherein the operation to be executed is a translation operation for moving the location of said three-dimensional object to another location in three-dimensional space including the additional step of:

specifying the location in three-dimensional space of the location of said three-dimensional reference point to which said object is to be moved relative to said reference point.

3. The method claimed in claim 1 wherein the operation to be executed is a rotation operation for rotating the three-dimensional object relative to said selected three-dimensional reference point including the additional step of:

specifying the angles in three-dimensional space through which said object is to be rotated relative to said reference point.

4. The method claimed in claim 1 wherein the operation to be executed is a copy operation for reproducing the three-dimensional object at another location in three-dimensional space including the additional step of:

specifying the location in three-dimensional space at which said object is to be reproduced relative to said reference point.

5. The method claimed in claim 1 wherein the operation to be executed is an attach operation for attaching at the reference point of said three-dimensional object another graphic entity including the additional step of:

specifying a graphic entity to be attached to said three-dimensional reference point.

6. The method claimed in claim 1 wherein the operation to be executed is a scaling operation for changing dimensions of said three-dimensional object relative to said three-dimensional reference point including the additional step of:

specifying the scaling factors in three-dimensional space of the three-dimensional object relative to said reference point.

7. The method claimed in claim 1 wherein the operation to be executed is an operation for shifting the location and direction of the viewing point of said three-dimensional object in three-dimensional space including the additional step of:

specifying the location in three-dimensional space relative to said three-dimensional reference point to which to move said viewing point.

8. In a graphics display system representing three-dimensional objects on a two-dimensional display screen, means for selecting three-dimensional coordinates of a point on a three-dimensional object as a reference point for the execution of an operation relative to said three-dimensional objects, the combination comprising:

first means for controlling selection of a displayed point corresponding to a three-dimensional reference point;

second means for controlling determination of the two-dimensional coordinates of the displayed point relative to a display surface;

third means for controlling conversion of stored three-dimensional coordinates corresponding to displayed points into two-dimensional coordinates relative to the display surface;

fourth means for controlling comparison of the coordinates converted by said third means to the coordinates determined by the second means; and

fifth means for controlling the execution of said operation relative to said three-dimensional reference point having two-dimensional coordinates corresponding to the displayed point selected by the first means as determined by an equality in the fourth means.

9. The combination claimed in claim 8 wherein the operation to be executed is a translation operation for moving the location of said three-dimensional object to another location in three-dimensional space including the additional means:

sixth means for controlling specifying the location in three-dimensional space of the location of said three-dimensional reference point to which said object is to be moved relative to said reference point.

10. The combination claimed in claim 8 wherein the operation to be executed is a rotation operation for rotating the three-dimensional object relative to said selected three-dimensional reference point including the additional means:

sixth means for controlling specifying the angles in three-dimensional space through which said object is to be rotated relative to said reference point.

11. The combination claimed in claim 8 wherein the operation to be executed is a copy operation for reproducing the three-dimensional object at another location in three-dimensional space including the additional step of:

sixth means for controlling specifying the location in three-dimensional space at which said object is to be reproduced relative to said reference point.

12. The combination claimed in claim 8 wherein the operation to be executed is an attach operation for attaching at the reference point of said three-dimensional object another graphic entity including the additional means:

sixth means for controlling specifying a graphic entity to be attached to said three-dimensional reference point.

13. The combination claim in claim 8 wherein the operation to be executed is a scaling operation for changing dimensions of said three-dimensional object relative to said three-dimensional reference point including the additional means:

sixth means for controlling specifying the scaling factors in three-dimensional space of the three-dimensional object relative to said reference point.

14. The combination claimed in claim 8 wherein the operation to be executed is an operation for shifting the location and direction of the viewing point of said three-dimensional object in three-dimensional space including the additional step of:

sixth means for controlling specifying the location in three-dimensional space relative to said threedimensional reference point to which to move said viewing point.