Re-adding Topics to SVN

java/examples/Topics/Simulate/MultipleParticleSystems/CrazyParticle.pde

@@ -0,0 +1,47 @@
+// A subclass of Particle
+
+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(PVector 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.mag()) / 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();
+  }
+}
+

java/examples/Topics/Simulate/MultipleParticleSystems/MultipleParticleSystems.pde

@@ -0,0 +1,50 @@
+/**
+ * Multiple Particle Systems
+ * 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. 
+ */
+ 
+ArrayList psystems;
+
+void setup() {
+  size(640, 360);
+  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 PVector(mouseX,mouseY)));
+}
+
+
+
+
+
+
+
+
+
+
+

java/examples/Topics/Simulate/MultipleParticleSystems/Particle.pde

@@ -0,0 +1,57 @@
+// A simple Particle class
+
+class Particle {
+  PVector loc;
+  PVector vel;
+  PVector acc;
+  float r;
+  float timer;
+
+  // One constructor
+  Particle(PVector a, PVector v, PVector l, float r_) {
+    acc = a.get();
+    vel = v.get();
+    loc = l.get();
+    r = r_;
+    timer = 100.0;
+  }
+  
+  // Another constructor (the one we are using here)
+  Particle(PVector l) {
+    acc = new PVector(0,0.05,0);
+    vel = new PVector(random(-1,1),random(-2,0),0);
+    loc = l.get();
+    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);
+    stroke(255,timer);
+    fill(100,timer);
+    ellipse(loc.x,loc.y,r,r);
+  }
+  
+  // Is the particle still useful?
+  boolean dead() {
+    if (timer <= 0.0) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+}

java/examples/Topics/Simulate/MultipleParticleSystems/ParticleSystem.pde

@@ -0,0 +1,51 @@
+// An ArrayList is used to manage the list of Particles 
+
+class ParticleSystem {
+
+  ArrayList particles;    // An arraylist for all the particles
+  PVector origin;        // An origin point for where particles are birthed
+
+  ParticleSystem(int num, PVector v) {
+    particles = new ArrayList();              // Initialize the arraylist
+    origin = v.get();                        // Store the origin point
+    for (int i = 0; i < num; i++) {
+      // We have a 50% chance of adding each kind of particle
+      if (random(1) < 0.5) {
+        particles.add(new CrazyParticle(origin)); 
+      } else {
+        particles.add(new Particle(origin)); 
+      }
+    }
+  }
+
+  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;
+    }
+  }
+
+}
+