Merge pull request #1646 from ybakos/example_ParticleSystem

Example particle system

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

@@ -12,7 +12,6 @@ class CrazyParticle extends 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
@@ -21,27 +20,21 @@ class CrazyParticle extends Particle {
   void update() {
     super.update();
     // Increment rotation based on horizontal velocity
-    float theta_vel = (vel.x * vel.mag()) / 10.0f;
+    float theta_vel = (velocity.x * velocity.mag()) / 10.0f;
     theta += theta_vel;
   }
 
-  // Override timer
-  void timer() {
-    timer -= 0.5;
-  }
-  
-  // Method to display
-  void render() {
+  // This display() method overrides the parent class display() method
+  void display() {
     // Render the ellipse just like in a regular particle
-    super.render();
-
+    super.display();
     // Then add a rotating line
     pushMatrix();
-    translate(loc.x,loc.y);
+    translate(location.x,location.y);
     rotate(theta);
-    stroke(255,timer);
+    stroke(255,lifespan);
     line(0,0,25,0);
     popMatrix();
   }
-}
 
+}

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

@@ -1,13 +1,13 @@
 /**
  * Multiple Particle Systems
- * by Daniel Shiffman.  
- * 
+ * by Daniel Shiffman.
+ *
  * Click the mouse to generate a burst of particles
- * at mouse location. 
- * 
+ * 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. 
+ * Note use of Inheritance and Polymorphism here.
  */
 
 ArrayList<ParticleSystem> systems;
@@ -24,7 +24,6 @@ void draw() {
     ps.run();
     ps.addParticle();
   }
-
   if (systems.isEmpty()) {
     fill(255);
     textAlign(CENTER);
@@ -35,13 +34,3 @@ void draw() {
 void mousePressed() {
   systems.add(new ParticleSystem(1, new PVector(mouseX, mouseY)));
 }
-
-
-
-
-
-
-
-
-
-

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

@@ -31,14 +31,10 @@ class Particle {
     fill(255,lifespan);
     ellipse(location.x,location.y,8,8);
   }
-  
+
   // Is the particle still useful?
   boolean isDead() {
-    if (lifespan < 0.0) {
-      return true;
-    } else {
-      return false;
-    }
+    return (lifespan < 0.0);
   }
-}
 
+}

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

@@ -1,4 +1,6 @@
-// An ArrayList is used to manage the list of Particles 
+// An ArrayList is used to manage the list of Particles
+// An Iterator is used to remove "dead" particles while iterating over the list
+import java.util.Iterator;
 
 class ParticleSystem {
 
@@ -14,7 +16,7 @@ class ParticleSystem {
   }
 
   void run() {
-    // Cycle through the ArrayList using Iterator we are deleting
+    // Cycle through the ArrayList using Iterator, because we are deleting while iterating
     Iterator<Particle> it = particles.iterator();
     while (it.hasNext()) {
       Particle p = it.next();
@@ -26,7 +28,14 @@ class ParticleSystem {
   }
 
   void addParticle() {
-    particles.add(new Particle(origin));
+    Particle p;
+    // Add either a Particle or CrazyParticle to the system
+    if (int(random(0, 2)) == 0) {
+      p = new Particle(origin);
+    } else {
+      p = new CrazyParticle(origin);
+    }
+    particles.add(p);
   }
 
   void addParticle(Particle p) {
@@ -35,11 +44,7 @@ class ParticleSystem {
 
   // A method to test if the particle system still has particles
   boolean dead() {
-    if (particles.isEmpty()) {
-      return true;
-    } else {
-      return false;
-    }
+    return particles.isEmpty();
   }
 
-}
+}