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# Method for Drawing an Ellipse on an Interactive Terminal

IP.com Disclosure Number: IPCOM000038494D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 24K

IBM

## Related People

Cross, MR: AUTHOR [+2]

## Abstract

A method is described to allow a user of an interactive terminal to rubberband an ellipse around a screen such that: (1) the user can intuitively predict instantaneous changes in ellipse orientation and in ellipse size as a function of mouse movement, and (2) both ellipse size and ellipse orientation are completely defined after the second click of the mouse button. Fig. 1 denotes the mouse position at the start of the first click on the mouse button. At each time t during the first click, the user sees on his screen an ellipse with the following properties: (1) Supposing that P(t) denoted the pointing cursor's position at time t, the line between P1 and P(t) forms the A axes of the ellipse.

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Method for Drawing an Ellipse on an Interactive Terminal

A method is described to allow a user of an interactive terminal to rubberband an ellipse around a screen such that: (1) the user can intuitively predict instantaneous changes in ellipse orientation and in ellipse size as a

function of mouse movement, and (2) both ellipse size and ellipse orientation are completely defined after the second click of the mouse

button. Fig. 1 denotes the mouse position at the start of the first click on the mouse button. At each time t during the first click, the user sees on his screen an ellipse with the following properties: (1) Supposing that P(t) denoted the pointing cursor's position at time t, the line between P1 and P(t) forms

the A axes of the ellipse. (2) The length of its second (transverse) axis B is half the length of its first axis, as shown in Fig. 2. Until the first click ends, both P(t) and the length of A axis can change. However, when the first click ends, the first axis is fixed during the remainder of this operation. Also, at the end of the first click, the orientation of the ellipse is fixed, since the user directly changes the slope of the ellipse's A axis as he moves P(t) around. At the end of the first click, the pointing cursor is also repositioned to a point Q1 at the intersection of the ellipse and its transverse axis. If the user were to begin and end the second click without moving the mouse, then the ellipse creation operation ends with the first...