I noticed a nice example on this site of a particle system in processing. I copied the code and compiled it in processing, but then I noticed that the arrows don't fade out there, while it does in the pre-compiled web applet. The same thing I noticed with numerous other applets that include line transparency, one of them being the MSA fluid demo. The lines don't fade out. Here's a code to confirm for any mac users. Do the arrows fade out? I tried this on windows and they did.
Code:
ParticleSystem ps;
void setup() {
size(640, 360);
colorMode(RGB, 255, 255, 255, 100);
ps = new ParticleSystem(1, new PVector(width/2,height/2,0));
smooth();
}
void draw() {
background(0);
ps.run();
ps.addParticle(mouseX,mouseY);
}
// 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
PVector origin; // An origin point for where particles are born
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++) {
particles.add(new Particle(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(float x, float y) {
particles.add(new Particle(new PVector(x,y)));
}
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;
}
}
}
// A simple Particle class
class Particle {
PVector loc;
PVector vel;
PVector acc;
float r;
float timer;
// 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);
displayVector(vel,loc.x,loc.y,10);
}
// Is the particle still useful?
boolean dead() {
if (timer <= 0.0) {
return true;
} else {
return false;
}
}
void displayVector(PVector v, float x, float y, float scayl) {
pushMatrix();
float arrowsize = 4;
// Translate to location to render vector
translate(x,y);
stroke(255);
// Call vector heading function to get direction (note that pointing up is a heading of 0) and rotate
rotate(v.heading2D());
// Calculate length of vector & scale it to be bigger or smaller if necessary
float len = v.mag()*scayl;
// Draw three lines to make an arrow (draw pointing up since we've rotate to the proper direction)
line(0,0,len,0);
line(len,0,len-arrowsize,+arrowsize/2);
line(len,0,len-arrowsize,-arrowsize/2);
popMatrix();
}
}
EDIT: Well, at least post if you have confirmed this. If not, say so.