by Daniel Shiffman. Click the mouse to generate a burst of particles at mouse location. Each burst is one instance of a particle system with Particles and CrazyParticles (a subclass of Particle) Note use of Inheritance and Polymorphism here.
Original Processing.org Example: MultipleParticleSystems
// All Examples Written by Casey Reas and Ben Fry
// unless otherwise stated.
ArrayList psystems;
void setup() {
size(200,200);
frameRate(30);
colorMode(RGB,255,255,255,100);
psystems = new ArrayList();
smooth();
}
void draw() {
background(0);
// Cycle through all particle systems, run them and delete old ones
for (int i = psystems.size()-1; i >= 0; i--) {
ParticleSystem psys = (ParticleSystem) psystems.get(i);
psys.run();
if (psys.dead()) {
psystems.remove(i);
}
}
}
// When the mouse is pressed, add a new particle system
void mousePressed() {
psystems.add(new ParticleSystem(int(random(5,25)),new Vector3D(mouseX,mouseY)));
}
// A subclass of Particle
// Created 2 May 2005
class CrazyParticle extends Particle {
// Just adding one new variable to a CrazyParticle
// It inherits all other fields from "Particle", and we don't have to retype them!
float theta;
// The CrazyParticle constructor can call the parent class (super class) constructor
CrazyParticle(Vector3D l) {
// "super" means do everything from the constructor in Particle
super(l);
// One more line of code to deal with the new variable, theta
theta = 0.0;
}
// Notice we don't have the method run() here; it is inherited from Particle
// This update() method overrides the parent class update() method
void update() {
super.update();
// Increment rotation based on horizontal velocity
float theta_vel = (vel.x * vel.magnitude()) / 10.0f;
theta += theta_vel;
}
// Override timer
void timer() {
timer -= 0.5;
}
// Method to display
void render() {
// Render the ellipse just like in a regular particle
super.render();
// Then add a rotating line
pushMatrix();
translate(loc.x,loc.y);
rotate(theta);
stroke(255,timer);
line(0,0,25,0);
popMatrix();
}
}
// A simple Particle class
class Particle {
Vector3D loc;
Vector3D vel;
Vector3D acc;
float r;
float timer;
// One constructor
Particle(Vector3D a, Vector3D v, Vector3D l, float r_) {
acc = a.copy();
vel = v.copy();
loc = l.copy();
r = r_;
timer = 100.0;
}
// Another constructor (the one we are using here)
Particle(Vector3D l) {
acc = new Vector3D(0,0.05,0);
vel = new Vector3D(random(-1,1),random(-2,0),0);
loc = l.copy();
r = 10.0;
timer = 100.0;
}
void run() {
update();
render();
}
// Method to update location
void update() {
vel.add(acc);
loc.add(vel);
timer -= 1.0;
}
// Method to display
void render() {
ellipseMode(CENTER);
noStroke();
fill(255,timer);
ellipse(loc.x,loc.y,r,r);
}
// Is the particle still useful?
boolean dead() {
if (timer <= 0.0) {
return true;
} else {
return false;
}
}
}
// A class to describe a group of Particles
// An ArrayList is used to manage the list of Particles
class ParticleSystem {
ArrayList particles; // An arraylist for all the particles
Vector3D origin; // An origin point for where particles are birthed
ParticleSystem(int num, Vector3D v) {
particles = new ArrayList(); // Initialize the arraylist
origin = v.copy(); // Store the origin point
for (int i = 0; i < num; i++) {
particles.add(new CrazyParticle(origin)); // Add "num" amount of particles to the arraylist
}
}
void run() {
// Cycle through the ArrayList backwards b/c we are deleting
for (int i = particles.size()-1; i >= 0; i--) {
Particle p = (Particle) particles.get(i);
p.run();
if (p.dead()) {
particles.remove(i);
}
}
}
void addParticle() {
particles.add(new Particle(origin));
}
void addParticle(Particle p) {
particles.add(p);
}
// A method to test if the particle system still has particles
boolean dead() {
if (particles.isEmpty()) {
return true;
} else {
return false;
}
}
}
// Simple Vector3D Class
public class Vector3D {
public float x;
public float y;
public float z;
Vector3D(float x_, float y_, float z_) {
x = x_; y = y_; z = z_;
}
Vector3D(float x_, float y_) {
x = x_; y = y_; z = 0f;
}
Vector3D() {
x = 0f; y = 0f; z = 0f;
}
void setX(float x_) {
x = x_;
}
void setY(float y_) {
y = y_;
}
void setZ(float z_) {
z = z_;
}
void setXY(float x_, float y_) {
x = x_;
y = y_;
}
void setXYZ(float x_, float y_, float z_) {
x = x_;
y = y_;
z = z_;
}
void setXYZ(Vector3D v) {
x = v.x;
y = v.y;
z = v.z;
}
public float magnitude() {
return (float) Math.sqrt(x*x + y*y + z*z);
}
public Vector3D copy() {
return new Vector3D(x,y,z);
}
public Vector3D copy(Vector3D v) {
return new Vector3D(v.x, v.y,v.z);
}
public void add(Vector3D v) {
x += v.x;
y += v.y;
z += v.z;
}
public void sub(Vector3D v) {
x -= v.x;
y -= v.y;
z -= v.z;
}
public void mult(float n) {
x *= n;
y *= n;
z *= n;
}
public void div(float n) {
x /= n;
y /= n;
z /= n;
}
public void normalize() {
float m = magnitude();
if (m > 0) {
div(m);
}
}
public void limit(float max) {
if (magnitude() > max) {
normalize();
mult(max);
}
}
public float heading2D() {
float angle = (float) Math.atan2(-y, x);
return -1*angle;
}
public Vector3D add(Vector3D v1, Vector3D v2) {
Vector3D v = new Vector3D(v1.x + v2.x,v1.y + v2.y, v1.z + v2.z);
return v;
}
public Vector3D sub(Vector3D v1, Vector3D v2) {
Vector3D v = new Vector3D(v1.x - v2.x,v1.y - v2.y,v1.z - v2.z);
return v;
}
public Vector3D div(Vector3D v1, float n) {
Vector3D v = new Vector3D(v1.x/n,v1.y/n,v1.z/n);
return v;
}
public Vector3D mult(Vector3D v1, float n) {
Vector3D v = new Vector3D(v1.x*n,v1.y*n,v1.z*n);
return v;
}
public float distance (Vector3D v1, Vector3D v2) {
float dx = v1.x - v2.x;
float dy = v1.y - v2.y;
float dz = v1.z - v2.z;
return (float) Math.sqrt(dx*dx + dy*dy + dz*dz);
}
}