Processing Month, Day 13 - Regular Polygons

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.

Download

Download the example for Procesing Day 13, Regular Polygons.