# Composite Objects

Composite Objects

An object can include several other objects. Creating such composite objects is a good way to use the principles of modularity and build higher levels of abstraction within a program.

```
EggRing er1, er2;

void setup() {
size(640, 360);
er1 = new EggRing(width*0.45, height*0.5, 0.1, 120);
er2 = new EggRing(width*0.65, height*0.8, 0.05, 180);
}

void draw() {
background(0);
er1.transmit();
er2.transmit();
}

class Egg {
float x, y; // X-coordinate, y-coordinate
float tilt; // Left and right angle offset
float angle; // Used to define the tilt
float scalar; // Height of the egg

// Constructor
Egg(float xpos, float ypos, float t, float s) {
x = xpos;
y = ypos;
tilt = t;
scalar = s / 100.0;
}

void wobble() {
tilt = cos(angle) / 8;
angle += 0.1;
}

void display() {
noStroke();
fill(255);
pushMatrix();
translate(x, y);
rotate(tilt);
scale(scalar);
beginShape();
vertex(0, -100);
bezierVertex(25, -100, 40, -65, 40, -40);
bezierVertex(40, -15, 25, 0, 0, 0);
bezierVertex(-25, 0, -40, -15, -40, -40);
bezierVertex(-40, -65, -25, -100, 0, -100);
endShape();
popMatrix();
}
}

class Ring {

float x, y; // X-coordinate, y-coordinate
float diameter; // Diameter of the ring
boolean on = false; // Turns the display on and off

void start(float xpos, float ypos) {
x = xpos;
y = ypos;
on = true;
diameter = 1;
}

void grow() {
if (on == true) {
diameter += 0.5;
if (diameter > width*2) {
diameter = 0.0;
}
}
}

void display() {
if (on == true) {
noFill();
strokeWeight(4);
stroke(155, 153);
ellipse(x, y, diameter, diameter);
}
}
}

class EggRing {
Egg ovoid;
Ring circle = new Ring();

EggRing(float x, float y, float t, float sp) {
ovoid = new Egg(x, y, t, sp);
circle.start(x, y - sp/2);
}

void transmit() {
ovoid.wobble();
ovoid.display();
circle.grow();
circle.display();
if (circle.on == false) {
circle.on = true;
}
}
}
```

## Functions Used

ellipse()

Draws an ellipse (oval) to the screen

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popMatrix()

Pops the current transformation matrix off the matrix stack

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rotate()

Rotates the amount specified by the angle parameter

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fill()

Sets the color used to fill shapes

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size()

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

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cos()

Calculates the cosine of an angle

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stroke()

Sets the color used to draw lines and borders around shapes

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vertex()

All shapes are constructed by connecting a series of vertices

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beginShape()

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

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setup()

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

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strokeWeight()

Sets the width of the stroke used for lines, points, and the border around shapes

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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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noFill()

Disables filling geometry

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bezierVertex()

Specifies vertex coordinates for Bezier curves

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endShape()

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

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noStroke()

Disables drawing the stroke (outline)

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background()

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

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pushMatrix()

Pushes the current transformation matrix onto the matrix stack

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scale()

Increases or decreases the size of a shape by expanding and contracting vertices

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