The *Ellipse Tool* allows one to draw ellipses,
circles, and arcs. Select the tool by
clicking on the
icon (**F5** or **e**) in the *Tool Box*.
To draw an ellipse or arc, use a **Left Mouse
Drag**. An ellipse will be drawn with the sides touching a
rectangular box defined by the starting and stopping points of the
drag. To force a circle to be drawn, hold down the
**Ctrl** while dragging the mouse. This also allows
ellipses with a height to width or width to height ratio that is
either an integer or in the “Golden Ratio” to
be drawn. Holding the **Shift** key down while dragging
will create an ellipse centered around the starting point. Holding
down the **Alt** key while dragging will create an
ellipse with the circumference passing through the start and end
points of the drag. Using
**Alt**+**Ctrl** while
dragging will create a circle with a diameter defined by the
distance between the start and stop point of the drag.

When an ellipse is selected and the *Ellipse Tool* is active, the
ellipse will have a set of handles (small squares and circles) that
can be used to resize it or convert it to an arc. (The handles are
also available if one of other shape *Tools* or
the *Node Tool* is active.)

To change the size of the ellipse, drag the handle at the top or
left. The **Ctrl** key can be used to force the
ellipse to be a circle.

To convert an ellipse into an arc, use the two
*Arc* handles. Initially both handles are on top
of each other. Drag one handle to set one end of the arc, then drag
the second handle to set the other end. Holding down the
**Ctrl** key while dragging an
*Arc* handle will force the angle of the arc to
begin or end at a multiple of the *Rotation snap angle* (15° by default).

If an *Arc* handle is dragged with the pointer
outside the curve of the virtual ellipse, the arc will be defined
with a closed path that has a wedge that extends to the center of
curvature (as shown above). If the *Arc* handle
is dragged with the pointer inside the curve, the path defining the
arc will start and stop at the two *Arc* handles, as shown below.

An arc can also be defined using the settings in the *Tool Controls*
when the *Ellipse Tool* is selected. The settings will affect any
ellipse or arc that is selected as well as any that are drawn
afterward. The *Start* and
*End* angles are defined in degrees and are
measured in the *clockwise* direction starting at
the *x*-axis. There are two buttons that toggle arcs between
opened (
) and closed (
)
(switchable if either angle is not zero).
There is also a button to reset an arc to an ellipse (
).

© 2005-2011 Tavmjong Bah. | Get the Book or EBook. |