# Regular Polygon

Regular Polygon

What is your favorite? Pentagon? Hexagon? Heptagon? No? What about the icosagon? The polygon() function created for this example is capable of drawing any regular polygon. Try placing different numbers into the polygon() function calls within draw() to explore.

```
void setup() {
size(640, 360);
}

void draw() {
background(102);

pushMatrix();
translate(width*0.2, height*0.5);
rotate(frameCount / 200.0);
polygon(0, 0, 82, 3);  // Triangle
popMatrix();

pushMatrix();
translate(width*0.5, height*0.5);
rotate(frameCount / 50.0);
polygon(0, 0, 80, 20);  // Icosahedron
popMatrix();

pushMatrix();
translate(width*0.8, height*0.5);
rotate(frameCount / -100.0);
polygon(0, 0, 70, 7);  // Heptagon
popMatrix();
}

void polygon(float x, float y, float radius, int npoints) {
float angle = TWO_PI / npoints;
beginShape();
for (float a = 0; a < TWO_PI; a += angle) {
float sx = x + cos(a) * radius;
float sy = y + sin(a) * radius;
vertex(sx, sy);
}
endShape(CLOSE);
}```

## Functions Used

size()

Defines the dimension of the display window width and height in units of pixels

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vertex()

All shapes are constructed by connecting a series of vertices

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pushMatrix()

Pushes the current transformation matrix onto the matrix stack

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sin()

Calculates the sine of an angle

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popMatrix()

Pops the current transformation matrix off the matrix stack

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setup()

The setup() function is run once, when the program starts

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beginShape()

Using the beginShape() and endShape() functions allow creating more complex forms

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rotate()

Rotates the amount specified by the angle parameter

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cos()

Calculates the cosine of an angle

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translate()

Specifies an amount to displace objects within the display window

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draw()

Called directly after setup(), the draw() function continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called

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endShape()

The endShape() function is the companion to beginShape() and may only be called after beginShape()

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background()

The background() function sets the color used for the background of the Processing window

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