Interactive computer graphics system for making precise drawings

• US 5,490,241 A
• Filed: 08/24/1990
• Issued: 02/06/1996
• Est. Priority Date: 10/06/1989
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Mallgren, William R., Donaldson, Janaia M.
• Primary Examiner(s): Herndon, Heather R,
• Assistant Examiner(s): FETTING, ANTON W
• Application Number:
  US07/573,085
• Time in Patent Office: 1,992 Days
• Field of Search: 395/133, 395/140, 395/141, 395/142, 395/143, 395/155, 395/161
• US Class Current: 345/440
• CPC Class Codes: G06F 3/04842 Selection of displayed objects or displayed text elements G06F3/0482 takes precedence
• CPC Class Codes: G06F 3/04845 for image manipulation, e.g. dragging, rotation, expansion or change of colour
• CPC Class Codes: G06T 19/20 Editing of 3D images, e.g. changing shapes or colours, aligning objects or positioning parts
• CPC Class Codes: Y10S 715/964 CAD or CAM, e.g. interactive design tools

Abstract

A computer-aided illustration system and method emulate the set of tools that are typically available to the traditional technical illustrator and also provide the user with the ability to easily create illustrations in various two-dimensional projections, including paraline and perspective projections. The techniques described include: (1) providing moving polar grids which restrict a drawing to a user-specified geometry; (2) combining arbitrary user-specified directional constraints with several types of gravity, in a manner which enables a user to easily create new objects in alignment with previously drawn objects; (3) interrelating constraint systems and geometries (as delineated in the polar grids) with gravity, thereby providing the user with an effortless way to create objects with complex geometric interdependencies; and (4) adapting tools from linear geometry to work in non-linear projection planes (paraline and perspective).

Claims

1. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, a method for assisting the creation and editing of illustrations comprising the steps of:

selecting a geometric mode from a set of geometric modes, at least one of the geometric modes of said set of geometric modes being adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object;

displaying on said display a grid representing the selected geometric mode, the grid having an origin;

placing a control point at a position on the displayed grid, said position being a point on said grid nearest to the cursor; and

moving automatically the grid origin to the placed control point.

2. The method of claim 1 wherein said

set of geometric modes includes a geometric mode selected from the group consisting of linear, polar, paraline, and perspective geometric modes.

3. The method of claim 1 further comprising:

displaying a crosshairs representing the selected geometric mode.

4. The method of claim 1 further comprising:

placing a second control point at a second position on the displayed grid, thereby defining a user-specified angle;

setting an angle with respect to an axis of the displayed grid, the angle being equal to the user-specified angle, the angle representing a directional constraint; and

constraining a next control point to lie at a position corresponding to the cursor on a line passing through the origin of the displayed grid and having a direction defined by the directional constraint.

5. The method of claim 1 wherein said selected geometric mode is a paraline geometric mode that defines three angles, and further comprising the step of:

using the moved grid origin, a grid distance unit, and said three angles to determine a moved grid.

6. The method of claim 1 wherein said selected geometric mode is a perspective geometric mode that defines at least one vanishing point, and further comprising the step of:

using a line passing through the moved grid origin and said at least one vanishing point to define said perspective geometric mode.

7. The method of claim 1 wherein said at least one geometric mode adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object is selected from the group consisting of paraline and perspective geometric modes.

8. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, a method for assisting the creation and editing of illustrations comprising the steps of:

selecting a geometric mode from a set of geometric modes, at least one of the geometric modes of said set of geometric modes being adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object;

displaying on said display a grid and at least one object, said grid representing said selected geometric mode;

setting a hit radius equal to a particular distance from said cursor;

if a portion of said at least one object is located within the hit radius of the cursor, testing said portion of said at least one object for an intersection with said grid, said intersection being located within said hit radius of the cursor; and

if said intersection is found, constraining a control point to lie at a position on said intersection.

9. The method of claim 8 further comprising:

if said intersection is found, highlighting on said display said intersection as feedback to a user.

10. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points, a method for assisting a user in the creation and editing of illustrations comprising the steps of:

(a) providing the user with an ability to select a geometric mode from a set of geometric modes, and displaying a grid representing the selected geometric mode on the display device responsively to an exercise by the user of said selecting ability;

(b) providing the user with an ability to specify an arbitrary angle representing a directional constraint, and selecting said angle responsively to an exercise by the user of said specifying ability;

(c) setting a hit radius equal to a particular distance from said cursor;

(d) displaying on said display at least one object capable of being described by a plurality of control points; and

(e) if a portion of said at least one object is located within the hit radius of the cursor,

testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of said cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;

if said first point is not found, testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of said cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;

if said second point is not found, testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said angle, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of said cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;

if said third point is not found, testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of said cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point; and

if said fourth point is not found, constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor.

11. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing a plurality of control points, a method for assisting a user in the creation and editing of illustrations by constraining the placement of said plurality of control points comprising the steps of:

defining a plurality of planes representing a projection from three dimension into two dimensions by a cube having a plurality of faces;

selecting one of said faces; and

constraining said plurality of control points to lie in a plane defined by said selected face;

wherein said constraining step comprises;

selecting an object on said display in said plane;

selecting a transformation mode adapted to facilitate a graphical transformation of said selected object;

placing at least one control point at a position in said plane; and

in response to said placed control point, effecting said graphical transformation on said selected object according to said selected transformation mode in said plane.

12. The method of claim 11 wherein said graphical transformation is an affine transformation.

13. The method of claim 11 wherein said graphical transformation is selected from the group consisting of stretch, shear, flip, scale, rotate, and move transformations.

14. A computer-aided drawing system comprising:

a computer having a memory and a processor;

a display device coupled to said computer;

a cursor-control device coupled to said computer for moving a cursor on said display device;

means for selecting a geometric mode from a set of geometric modes including a geometric mode selected from the group consisting of linear, angular, paraline, and perspective geometric modes;

means for displaying a grid representing the selected geometric mode on the display device, the grid having an origin;

means for placing a control point at a position on the displayed grid nearest to the cursor; and

means for moving the grid origin to the placed control point in response to said placing means.

15. A computer-aided drawing system comprising:

a computer having a processor and a memory;

a display coupled to said computer for displaying illustrations to a user;

a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points;

means for optionally selecting a geometric mode from a set of geometric modes and displaying a grid representing the selected geometric mode on the display;

means for optionally selecting a user-specified angle representing a directional constraint;

means for setting a hit radius equal to a particular distance from said cursor;

means for displaying on said display at least one object capable of being described by a plurality of control points;

means, responsive to whether a portion of said at least one object is located within the hit radius of the cursor, for testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of said cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;

means, responsive to said first point'"'"'s not being found, for testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of said cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;

means, responsive to said second point'"'"'s not being found, for testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said directional constraint, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of said cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;

means, responsive to said third point'"'"'s not being found, for testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of said cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point; and

means, responsive to said fourth point'"'"'s not being found, for constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor.

16. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, a method for assisting the creation and editing of illustrations with directional constraints comprising the steps of:

selecting an arbitrary angle representing a directional constraint; and

constraining a control point to lie at a position that is;

on a line passing through a point of origin and having a direction defined by the directional constraint, and

aligned with the cursor in an alignment selected from the group consisting of horizontal alignment and vertical alignment, said alignment selected consistently with placing said control point as near as possible to the cursor.

17. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, a method for assisting the creation and editing of illustrations comprising the steps of:

selecting a geometric mode from a set of geometric modes, at least one of the geometric modes of said set of geometric modes being adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object;

displaying on said display a grid representing the selected geometric mode; and

using the cursor to place a control point in relation to the displayed grid.

18. A computer-aided drawing system comprising:

a computer having a memory and a processor;

a display device coupled to said computer;

a cursor-control device coupled to said computer for moving a cursor on said display device;

means for selecting a geometric mode from a set of geometric modes, at least one of the geometric modes of said set of geometric modes being adapted to facilitate drawing in two dimensions a two-dimensional representation of a three-dimensional object;

means for displaying a grid representing the selected geometric mode on the display device; and

means, responsive to the selected geometric mode, for placing a control point in relation to the displayed grid.

19. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points, a method for assisting a user in the creation and editing of illustrations by constraining the placement of said plurality of control points comprising the steps of:

defining a plurality of planes to represent a projection from three dimensions into two dimensions;

selecting a plane from said plurality of planes;

selecting an object on said display in said selected plane;

selecting an affine transformation mode for effecting an affine transformation of said selected object;

placing at least one control point at a position in said selected plane;

performing a coordinate system transformation of said at least one control point and said selected object from a coordinate system of said selected plane to an orthogonal coordinate system;

in response to said at least one control point, effecting said affine transformation in said orthogonal coordinate system on said selected object; and

performing a coordinate system transformation of said selected object from said orthogonal coordinate system to said coordinate system of said selected plane.

20. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points, a method for assisting a user in the creation and editing of illustrations by constraining the placement of said plurality of control points comprising the steps of:

defining a plurality of planes to represent a projection from three dimensions into two dimensions;

selecting a plane from said plurality of planes;

selecting an arbitrary angle representing a directional constraint;

performing a coordinate system transformation of said angle from a coordinate system of said selected plane to an orthogonal coordinate system;

constraining at least one control point to lie in said selected plane according to said angle; and

performing a coordinate system transformation from said orthogonal coordinate system to said coordinate system of said selected plane.

21. The method of claim 20 further comprising the steps of:

performing a coordinate system transformation of;

a horizontal direction, and

a vertical direction, from said coordinate system of said selected plane to said orthogonal coordinate system;

further constraining said at least one control point to lie at a position that is aligned with the cursor in an alignment selected from the group consisting of horizontal alignment and vertical alignment, said alignment selected consistently with placing said at least one control point as near as possible to the cursor.

22. In a computer-aided drawing system having a display and a cursor-control means for positioning a cursor on the display, said cursor being suited for placing control points, a method for assisting a user in the creation and editing of illustrations comprising the steps of:

(a) providing the user with an ability to select a geometric mode from a set of geometric modes, and displaying a grid representing said selected geometric mode on the display device responsively to an exercise by the user of said selecting ability;

(b) providing the user with an ability to specify an angle representing a directional constraint, and selecting said angle responsively to an exercise by the user of said specifying ability;

(c) setting a hit radius equal to a particular distance from said cursor;

(d) if said angle is selected, constraining a next control point to lie at a position corresponding to the cursor on a line passing through the origin of the displayed grid and having a direction defined by the directional constraint;

(e) if a portion of at least one object capable of being described by a plurality of control points is displayed on said display within the hit radius of the cursor,

testing said portion of said at least one object for a first point representing at least one of said plurality of control points located within said hit radius of the cursor, and if said first point is found, constraining a next control point to lie at a position corresponding to said first point;

if said first point is not found, testing said portion of said at least one object for a second point representing an intersection with at least one other object, said second point being located within said hit radius of the cursor, and if said second point is found, constraining a next control point to lie at a position corresponding to said second point;

if said second point is not found, testing said portion of said at least one object for a third point representing an intersection with a line passing through a point of origin and having a direction defined by said directional constraint, said point of origin being the origin of the displayed grid if said geometric mode was selected, said third point being located within said hit radius of the cursor, and if said third point is found, constraining a next control point to lie at a position corresponding to said third point;

if said third point is not found, testing said portion of said at least one object for a fourth point representing an intersection with said grid, said fourth point being located within said hit radius of the cursor, and if said fourth point is found, constraining a next control point to lie at a position corresponding to said fourth point; and

if said fourth point is not found, constraining a next control point to lie at a position corresponding to said at least one object that is closest to said cursor;

(f) if said at least one object is not displayed within the hit radius of the cursor and said geometric mode is selected, placing a next control point corresponding to a position on said grid, said position being a point on said grid nearest to the cursor; and

(g) if said geometric mode is not selected, placing a next control point corresponding to the cursor.