# Processing Month, Day 13 - Regular Polygons

Posted by Jan Vantomme on 13 May 2011.
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Today we’re going to write a flexible function to draw regular polygons. As Processing only offers basic shapes like ellipses, rectangles and triangles, it might be handy to have a collection of functions to draw other shapes. The function for a regular polygon looks a lot like the algorithm we wrote on day 4, Stars.

The code below is the full function to draw a regular polygon. It takes a float for the radius, and an integer for the number of points.

``` void regularPolygon( float radius, int numPoints ){    float angle = TWO_PI / numPoints;    beginShape();    for (int i = 0; i < numPoints; i++) {        float x = cos( i * angle ) * radius;        float y = sin( i * angle ) * radius;        vertex( x, y );    }    endShape(CLOSE); }  ```

If you want to draw the polygon to the screen, you’ll need to use the @translate()@ function first. The function draws the regular polygon from its center. I’ve used a for-loop to draw a lot of polygons, so you can see how powerful a small function like this one can be.

``` translate( width/2, height/2 );for (int i = 0; i < 18; i++) {    regularPolygon( 10 + i * 10, 3 + i );}  ```

### Examples

The sketch is also available on OpenProcessing.