# Particles, Classes and Color

Play Particles, Classes and Color

## Description

See this sketch in action

We create a colorful particle field. We learn how to define a class for our Particle object and have each particle take care of its own properties, such as position and direction. We also explore the creation of dynamic colors and some rendering tricks to make the sketch more appealing.

The finished sketch for this lesson can be found below:

```int totalDots = 100;
Dot[] dots = new Dot[totalDots];
int width, height;
color fillColor;
float diameter = 6.0;

void setup() {
// DEFINE THE STAGE
width = 500;
height = 550;
size(width, height);
// THE SAME FILL IS USED FOR ALL DOTS
fillColor = color(255, 0, 0);
fill(fillColor);
noStroke();
// CREATE A COLLECTION OF DOTS
for (int i = 0; i < totalDots; i++) {
Dot d = new Dot();
d.x = random(width);
d.y = random(height);
d.vx = random(2.0) - 1.0;
d.vy = random(2.0) - 1.0;
dots[i] = d;
}
background(0);
};

void draw() {
fill(0, 25);
rect(0, 0, width, height);
float r = 255;
float g = 255;
float b = 255;
for (int i = 0; i < totalDots; i++) {
r = map(dots[i].x, 0, width, 0, 255);
g = map(dots[i].y, 0, height, 0, 255);
fill(r, g, b);
dots[i].update();
ellipse(dots[i].x, dots[i].y, diameter, diameter);
}
};

class Dot {
float x = 0.0;
float y = 0.0;
float vx = 0.0;
float vy = 0.0;
void update(){
// update the velocity
this.vx += random(2.0) - 1.0;
this.vx *= .96;
this.vy += random(2.0) - 1.0;
this.vy *= .96;
// update the position
this.x += this.vx;
this.y += this.vy;
// handle boundary collision
if (this.x > width) { this.x = width; this.vx *= -1.0; }
if (this.x < 0) { this.x = 0; this.vx *= -1.0; }
if (this.y > height) { this.y = height; this.vy *= -1.0; }
if (this.y < 0) { this.y = 0; this.vy *= -1.0; }
}
}
```