System and method for specifying elliptical parameters

Abstract

An interactive elliptical arc control system and method are disclosed. Three control points are provided—a center control point and two foci control points—that a user can interactively manipulate in order to specify and change the elliptical parameters involved. The center control point can control the radius of the ellipse in the x direction, while keeping constant the ratio of the radius of the ellipse in the y direction to the radius of the ellipse in the x direction. The center control point can also control the relationship of the sweep flag to the large arc flag involved. The two foci control points can control the ratio of the radius of the ellipse in the y direction to the radius of the ellipse in the x direction, the angle from the x-axis of the coordinate system to the x-axis of the ellipse, and the value of the sweep flag.

1 . A method for rendering an elliptical arc in response to user input, comprising: 
 receiving, via a pointing device of a graphical user interface (GUI), a first end point and a second end point for an elliptical arc;    receiving, via the pointing device of the GUI, a center point for the elliptical arc;    receiving, via the pointing device of the GUI, a foci point for the elliptical arc; and    rendering the elliptical arc passing through the first and second end points, and having a center at the center point and a semi-major axis along a line joining the center point and the foci point.    
     
     
         2 . The method of  claim 1 , further comprising: 
 receiving, via the pointing device of the GUI, a second foci point for the elliptical arc; and    rendering the elliptical arc having the semi-major axis along a line joining the center point and the second foci point.    
     
     
         3 . The method of  claim 1 , further comprising determining a radius of the ellipse along the semi-major axis and a radius of the ellipse along a semi-minor axis based on the received user input.  
     
     
         4 . The method of  claim 1 , further comprising determining an angle from an x-axis of a coordinate system of the GUI to an x-axis of the ellipse based on the received user input.  
     
     
         5 . The method of  claim 1 , further comprising the arc of the ellipse and a direction of the arc based on the received user input.  
     
     
         6 . A system for rendering an elliptical arc in response to user input, comprising: 
 a graphical user interface; and    a pointing device coupled to the graphical user interface, the graphical user interface operable to: 
 receive, via the pointing device, a first end point and a second end point for an elliptical arc;  
 receive, via the pointing device, a center point for the elliptical arc;  
 receive, via the pointing device, a foci point for the elliptical arc; and  
 render the elliptical arc passing through the first and second end points, and having a center at the center point and a semi-major axis along a line joining the center point and the foci point.  
   
     
     
         7 . The system of  claim 6 , wherein the graphical user interface is further operable to: 
 receive, via the pointing device of the GUI, a second foci point for the elliptical arc; and    render the elliptical arc having the semi-major axis along a line joining the center point and the second foci point.    
     
     
         8 . The system of  claim 6 , wherein the graphical user interface is further operable to determine the radius of the ellipse along the semi-major axis and a radius of the ellipse along a semi-minor axis based on the received user input.  
     
     
         9 . The system of  claim 6 , wherein the graphical user interface is further operable to determine an angle from an x-axis of a coordinate system of the GUI to the x-axis of the ellipse based on the received user input.  
     
     
         10 . The system of  claim 6 , wherein the graphical user interface is further operable to determine the arc of the ellipse and a direction of the arc based on the received user input.  
     
     
         11 . Software for rendering an elliptical arc in response to user input, the software being embodied in logic encoded in media and when executed operable to: 
 receive, via a pointing device of a GUI, a first end point and a second end point for an elliptical arc;    receive, via the pointing device of the GUI, a center point for the elliptical arc;    receive, via the pointing device of the GUI, a foci point for the elliptical arc;    render the elliptical arc passing through the first and second endpoints, and having a center at the center point and a semi-major axis along a line joining the center point and the foci point; and    determine a radius of the ellipse along the semi-major axis, a radius of the ellipse along a semi-minor axis and an angle from an x-axis of a coordinate system of the GUI to an x-axis of the ellipse based on the received user input.    
     
     
         12 . The software of  claim 11 , wherein the software is further operable to: 
 receive, via the pointing device of the GUI, a second foci point for the elliptical arc; and    render the elliptical arc having the semi-major axis along a line joining the center point and the second foci point.    
     
     
         13 . The software of  claim 11 , wherein the software is further operable to determine the radius of the ellipse along the semi-major axis and a radius of the ellipse along a semi-minor axis based on the received user input.  
     
     
         14 . The software of  claim 11 , wherein the software is further operable to determine an angle from an x-axis of a coordinate system of the GUI to the x-axis of the ellipse based on the received user input.  
     
     
         15 . The software of  claim 11 , wherein the software is further operable to determine the arc of the ellipse and a direction of the arc based on the received user input.  
     
     
         16 . A system for rendering an elliptical arc in response to user input, comprising: 
 means for receiving from a user a first end point and a second end point for an elliptical arc;    means for receiving from a user a center point for the elliptical arc;    means for receiving a foci point for the elliptical arc;    means for rendering the elliptical arc passing through the first and second end points, and having a center at the center point and a semi-major axis along a line joining the center point and the foci point; and    means for determining a radius of the ellipse along a semi-major axis, a radius of the ellipse along a semi-minor axis, an angle from an x-axis of a coordinate system of the GUI to the x-axis of the ellipse based on the received user input.