# Star

Star

The star() function created for this example is capable of drawing a wide range of different forms. Try placing different numbers into the star() 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);
star(0, 0, 5, 70, 3);
popMatrix();

pushMatrix();
translate(width*0.5, height*0.5);
rotate(frameCount / 400.0);
star(0, 0, 80, 100, 40);
popMatrix();

pushMatrix();
translate(width*0.8, height*0.5);
rotate(frameCount / -100.0);
star(0, 0, 30, 70, 5);
popMatrix();
}

void star(float x, float y, float radius1, float radius2, int npoints) {
float angle = TWO_PI / npoints;
float halfAngle = angle/2.0;
beginShape();
for (float a = 0; a < TWO_PI; a += angle) {
float sx = x + cos(a) * radius2;
float sy = y + sin(a) * radius2;
vertex(sx, sy);
sx = x + cos(a+halfAngle) * radius1;
sy = y + sin(a+halfAngle) * radius1;
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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