Creating ellipses or elliptical arcs

Press the ellipse tool button in order to create ellipses or elliptical arc s. The menu appears at the right end of the menu bar. The menu items, as shown below, consist of options to select the type of the ellipse, i.e., quarter, half or full ellipse. The . marked option is used for creation of ellipses and elliptical arcs. The option can be changed by selecting the menu item before or while the ellipse or elliptical arc being entered. The ellipse or elliptical arc is completed by entering 3 points, regardless of the type of the ellipse. The first point is the center of the ellipse or elliptical arc, and the second point is the starting point of the circumference. The line connecting these two points becomes the first radius, r1 as shown below. The third point is not necessarily on the circumference of the ellipse or elliptical arc, but determines the second radius, r2 and the plane on which the ellipse or elliptical arc lies. r2 is set as equal to the distance between the first and the third points. The three points form the plane on which the ellipse or elliptical arc lies. But they should not lie on a common straight line, in case which the ellipse or elliptical arc cannot be defined.

> Quarter

While this option is checked, an elliptical arc, with a quarter of an ellipse, is created by entering three points, as in the manner described above. The elliptical arc of this option has circumference with a central angle of 90  starting from the second input point and ending at the end of the second radius as shown below. When the second point is entered, a circle is drawn temporarily, with its center at the first point and with its radius connecting the first and the second points. The plane and the part of the ellipse consisting the arc are determined by the third point.

< Quarter ellipse >

> Half

While this option is checked, an elliptical arc, with a half of an ellipse, is created by entering three points, in the manner described above. The half ellipse has the c i rc u m f e rence starting from the second input point and is symmetric about the second radius as shown below. When the second point is entered, a temporary circle is drawn, with its center at the first point and with its radius connecting the first and the second points. The plane and the part of the ellipse consisting the arc are determined by the third point.

< Half ellipse >

> Full

While this option is checked, an ellipse is created by entering three points, as in the manner described above. The ellipse created by this option has circumference starting from the second input point and turning around back to this point. When the second point is entered, a circle is drawn, with its center at the first point and with its radius connecting the first and the second points. The plane and the second radius of the ellipse are determined by the third point.

< Full ellipse >