Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Reexamination Certificate
1998-06-05
2001-10-02
Sax, Steven (Department: 2173)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
C345S215000
Reexamination Certificate
active
06297798
ABSTRACT:
SOURCE CODE APPENDICES
A microfiche appendix (1/78) of Visual C++ language source code for a preferred embodiment (©1995 Intergraph) are filed herewith. A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
The present invention relates to a computer-aided drawing system. More particularly, the present invention relates to a system and method for reducing the number of different user commands needed to define an element to be drawn.
Computer-aided drawing packages are known in which a user interactively draws an object on a screen using a series of cursor manipulations and/or keyboard commands to define the shape and size of the object. Typically, one creates an illustration by combining basic geometric objects such as arcs, lines, circles etc. These packages find application in computer-aided design (CAD), for example.
Typically, the process of drawing an object begins with the user selecting a particular drawing command either via the keyboard or by use of a pointing device to access pull-down menus or a toolbar. The choice of initial command selects a basic geometric object to be drawn, whether it be a line, arc, or some other element. After the initial command, the user employs a pointing device, moving a cursor to specify a series of points that determine the size and shape of the object. The computer-aided drawing system interprets the point selections based on the initially selected command and draws the specified object accordingly.
The above description of the computer-aided drawing process will be made clearer with reference to a simple example. To draw a line segment, the user might begin by selecting a line drawing command by using a mouse to position a cursor over a line icon on a toolbar and then depressing a mouse button. The user would then position the cursor at a first point and again depress the mouse button. The drawing package would interpret this first selected point as the first endpoint of the line. The user would continue by positioning the cursor at a second point and depress the mouse button again. The computer-aided drawing package would interpret the second point as the second end of the line segment and draw the line segment to connect the first and second points.
In the above example, the user's actions may be interpreted by the drawing package unambiguously. The two points identified by the user clearly denote the endpoints of the line. Indeed, using the mouse in the above-described fashion is probably the most natural approach to line drawing for a user experienced with graphical user interfaces.
However, for other basic geometric objects, ambiguities may arise in interpreting user input. Consider the steps of drawing an arc. The user would begin by selecting an arc icon from the toolbar. The first point selected by the user is interpreted as a first end of the arc. Some drawing packages then interpret a second selected point as a midpoint of the arc and a third selected point as the endpoint of the arc. Others interpret the second point to be the endpoint and the third point to be the midpoint.
A problem thus arises in that users will bring their previous experience with arc drawing to a new drawing package and expect their cursor movements to be interpreted in accordance with a particular one of these alternative methods. Users will become confused if, e.g., the point they thought was selected to be an endpoint instead becomes a midpoint of the arc.
A possible solution is to present two distinct initial commands corresponding to the different methods of interpreting the second and third points. The user could select the preferred command at the outset, removing any ambiguities.
Increasing the number of commands in this way carries serious drawbacks. The arc example given above is but one example of the ambiguities that can arise in drawing objects. Thus, numerous extra commands would need to be added to pull-down menus and toolbars, increasing system complexity. The user would further need to be trained to consider the possible ways his actions could be interpreted and select a particular command accordingly.
SUMMARY OF THE INVENTION
The invention provides a method for resolving ambiguities in user input to a computer-aided drawing package. The number of necessary commands is therefore reduced. To draw an element, the user selects a particular drawing command. The user then manipulates a pointing device to select points that further define the position and shape. In accordance with the invention, the point selections can be interpreted in more than one way. A region surrounding at least one of the selected points is divided into so-called intent zones. After this point is selected, the drawing package monitors cursor movement through this region. The particular intent zone traversed by the cursor determines the interpretation of the point selections following the command. In accordance with the invention, the geometric arrangement of the intent zones may be varied to provide the most plausible interpretation of the user's actions.
In accordance with a first aspect of the invention, a user draws an arc by first selecting an arc command. The user then moves a cursor to a first desired endpoint of the arc and selects the point by depressing a mouse button or in some other way. The user then similarly selects a second point and a third point of the arc. A small circular region surrounding the second point is divided into two intent zones. A first intent zone may comprise the side of the circle facing toward the first point. A second intent zone may comprise the side of the circle facing away from the first intent zone.
If after defining the second point, the user moved the cursor through the first intent zone, the second point is interpreted to be an endpoint of the arc. If, on the other hand, the user had moved the cursor through the second intent zone, the third point is understood to be an endpoint. This response corresponds to the most plausible interpretation of the user's actions.
In accordance with a second aspect of the invention, a user draws an arc either tangent or perpendicular to an existing line. The user first selects an arc command. The user then selects a point on the existing line as a first endpoint of the arc. A second point and/or keyboard input further define the arc. A small circular region surrounding the first point is divided into four wedge shaped intent zones. First and second intent zones oppose one another, touching at the center of the circle, and are traversed by the existing line. Third and fourth intent zones occupy the gaps between the first and second intent zones.
If after the defining the first point, the user moved the cursor through either the first or second intent zones, the arc will be drawn tangent to the existing line. If on the other hand, the user had moved the cursor through one of the third or fourth intent zones, the arc will be drawn perpendicular to the existing line. Thus, through the use of intent zones, the invention combines two arc drawing commands into one without the use of special modes.
In accordance with a third aspect of the invention, a user draws an arc by first selecting an arc command, wherein a first point selected by the user defines the center of the arc. The user selects a second point to be a first endpoint of the arc. A third point selected by the user and/or keyboard input further defines the shape and/or extent of the arc. A region surrounding an imaginary line extending from the first point through the second point is divided into two intent zones. A first intent zone is the portion of the region above the imaginary line and the second intent zone lies below the imaginary line.
If after defining the second point
Blomqvist Per
Evans Charles
Mawby Eric
Schwartz John
Intergraph Corporation
Sax Steven
Townsend and Townsend / and Crew LLP
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