﻿ The Arcs / Sectors / Segments

# The Arcs / Sectors / Segments

Top  Previous  Next

FX Draw provides 5 arc tools - end points and point on the arc; centre and end points, four corner (elliptical) arcs, parabolic arcs and compass arcs.

Video - Drawing Arcs

Arcs, sectors and segments are all drawn with the same tool.  Any arc can be made into a sector or a segment by selecting the options in the properties.  As with circles and ellipses, there is more than one way to draw an arc.  Once drawn, all arcs share the same properties.

Every arc can have an arrowhead drawn at each end and one in the middle.  You can select a mark to show the centre of curvature.  On most arcs you can set the rotation and central angle of the arc explicitly.  You can choose to draw the arc or its associated sector or segment.  Finally, on most arcs you can choose to draw the major or minor arc defined by your control points.

Rotation is measured anti-clockwise from a horizontal line pointing to the right.  Negative rotations rotate the arc clockwise.  The central angle is the angle between the two arms of the arc.

One final major difference between the arc tools is that the four corner tool is the ONLY arc tool that can draw elliptical arcs.  The other three tools will always draw circular arcs.

Available Parameters for Arcs

\$centre                - centre of curvature

\$start

\$stop

\$length

\$sector                - area of sector defined by arc

\$segment                - area of segment defined by arc

\$angle                        - central angle

Available Parameters for Elliptical Arcs

\$centre                - centre of curvature

\$start

\$stop

\$length

\$minoraxis                - length of minor axis

\$majoraxis                - length of major axis

\$angle                        - central angle

\$eccentricity

# End Points & Point on Arc

This arc is defined by its two end points and any other point on the arc.

You can draw this arc in two ways.

 • Click AND HOLD the left mouse button – this determines one end of the arc.
 • Move the mouse (while holding the button) to the other end of your arc.  While you are moving the mouse, FX Draw will synthesize a third point and show you an arc.  Release the button when you are at the second point.
 • Click AND HOLD the left mouse button and move the mouse to a third point on your arc. As you move the mouse, FX Draw will draw an arc defined by your points.  Release the button when you are at the third point.

Alternatively you can click three times - once on each point.

# Centre & Two Ends

This arc is defined by its centre of curvature and its two end points.

## Drawing The Arc

 • Click AND HOLD the left mouse button – this defines the centre of curvature.
 • Move the mouse (while holding the button) to one end of your arc.  While you are moving the mouse, FX Draw will draw a light grey circle showing the current radius of the arc.

 • Release the mouse button when you are on one end of the arc.
 • Move the mouse - FX Draw will draw the current arc in a darker grey.

 • Click the mouse button when you are at the other end of the arc.

Minor and Major Arcs

If you select a centre/two ends arc, you will notice that there is an extra point on the arc.  A point you did not define.

FX Draw automatically generates this point so it can be sure about which side of the arc to shade - the minor or major side.  You can move this point and change the side to suit yourself.

# Four Corner (Elliptical) Arcs

The four corner arc tool is the ONLY way to draw elliptical arcs.  When you first draw a four corner arc,  you can force the tool to draw a circular arc by holding down the Shift key as you sweep out the rectangle.  In common with many FX Draw tools, holding down the Shift key forces the rectangle you sweep to a square.

As you sweep out a rectangle, FX Draw will show you a light grey ellipse that your arc will fit on.

Release the mouse button and move the cursor to one of the end points of the arc you require.  Click and hold the mouse button while moving the mouse button to the other end point.

Release the mouse button to define the arc.

## Minor and Major Arcs

If you select a four corner arc, you will notice that there is an extra point on the arc.  A point you didn't define.

FX Draw automatically generates this point so it can be sure about which side of the arc to shade - the minor or major side.  You can move this point and change the side to suit yourself.

# Parabolic Arcs

The parabolic arc tool draws a parabolic arc which is part of a parabola with a vertical axis. The three points define the two end points and a point on the parabolic arc.

You can draw this arc in two ways.

 • Click AND HOLD the left mouse button – this determines one end of the arc.
 • Move the mouse (while holding the button) to the other end of your arc.  While you are moving the mouse, FX Draw will synthesize a third point and show you an arc.  Release the button when you are at the second point.
 • Click AND HOLD the left mouse button and move the mouse to a third point on your arc. As you move the mouse, FX Draw will draw an arc defined by your points.  Release the button when you are at the third point.

Alternatively you can click three times - once on each point.

# Compass Arc

When you use a compass to draw an arc, you place the point on the centre, set the radius and draw - just like the centre/end points arc tool.

The thing that IS different about using a compass is that with a compass you can keep the same radius to draw more arcs.

That is what the Compass Arc tool does.  It is a Centre/End Points circle that remembers the radius.

The first time you use the compass arc tool it operates in exactly the same way as the centre/end points tool.

The second and subsequent times, you just click on the centre of the new arc.  The compass arc tool remembers the radius and marks the circle so you can set the end points.

The compass arc tool will remember the radius for as long as it is selected.

You can force the compass arc tool to reset its radius by:

a)        Right clicking on a compass drawn circle.

b)        Right clicking on a blank part of the drawing canvas.

Video - The Compass Like Tools