Recipe 7.10. Drawing Regular Polygons

Problem

You want to draw a regular polygon (a polygon where all sides are equal length) at runtime.

Solution

Use the Pen.drawRegularPolygon( ) method.

Discussion

You can create a method to draw a regular polygon using basic trigonometric ratios to determine the necessary angles and coordinates of the segments. Of course, since employing those trigonometric ratios requires quite a lot of code and you actually recall trigonometry, you'll likely find it much easier to simply use the drawRegularPolygon( ) method of the Pen class.

The drawRegularPolygon( ) accepts up to five parameters, described as follows:

x

The x coordinate of the center of the polygon.

y

The y coordinate of the center of the polygon.

sides

The number of sides in the polygon.

length

The length of each side in pixels.

rotation

The number of degrees by which the polygon should be rotated.

Once you have defined a Pen instance, you can quickly draw regular polygons with any number of sides (with a minimum of three sides, of course, to be a valid polygon):

var pen:Pen = new Pen(sampleSprite.graphics); // Draw a pentagon in which the sides are each 50 pixels pen.drawRegularPolygon(100, 100, 5, 50);

As with the other shape drawing methods in this chapter, you can create a filled polygon by invoking beginFill( ), beginGradientFill( ), or beginBitmapFill( ) before drawRegularPolygon( ), and invoking endFill( ) after drawRegularPolygon( ):

var pen:Pen = new Pen(sampleSprite.graphics); pen.beginFill(0xFF0000); pen.drawRegularPolygon(100, 100, 5, 50); pen.endFill(  );