Strings

final int NB_PARTICLES = 350;

final int W = 200;

final float MAX_PARTICLE_SPEED = 4;

int count = 0;

final int nbZ = 200;

int mode = 0;

​

float noiseZ;

float noiseSpeedZ;

float stepNoiseXY;

final float TP = TWO_PI;

myVector tabParticles[];

float coeffColor;

float margin = 20;

​

void setup() {

  size(400, 400, P3D);

  background(0);

  colorMode(HSB, 255);

  noFill();

  strokeWeight(3);

  initialize();

}

​

void initialize()

{

  float n;

  count = 0;

  noiseZ = random(123456);

  noiseSpeedZ = random(.01, .02) * (random(1) < .5 ? 1 : -1);

  coeffColor = random(.3);

  stepNoiseXY = random(.007, .013);

  tabParticles = new myVector[NB_PARTICLES];

  for (int i = 0; i < NB_PARTICLES; i++) {

    tabParticles[i] = new myVector();

  }

  background(0);

}

​

void draw() {

  background(0);

  noiseZ += noiseSpeedZ;

  PVector mouseVector = new PVector(mouseX, mouseY);

  translate(width/2, height/2);

  rotateY(PI+map(mouseX, 0, width, -TP, TP));

  rotateX(map(mouseY, 0, height, -TP, TP));

  translate(0, 0, -Math.min(count, nbZ)/2);

  for (int i = 0; i < NB_PARTICLES; i++) {

    tabParticles[i].update();

  }

  count++;

}

​

void mousePressed() {

  initialize();

}

​

class myVector {

  PVector pos, origin, speed = new PVector(0, 0, 0);

  PVector[] poss;

​

  myVector () {

    poss = new PVector[nbZ];

    pos = new PVector(random(-W/2, W/2), random(-W/2, W/2), 0);

    origin = pos.get();

  }

​

  void update() {

    float n;

    if (mode == 0) {

      n = noise(origin.x * stepNoiseXY, origin.y * stepNoiseXY, noiseZ);

      n = .8 * (n - .5);

      speed.x = n*2*cos(n * TP) * MAX_PARTICLE_SPEED;

      speed.y = n*2*sin((1-n) * TP) * MAX_PARTICLE_SPEED;

    } else {

      n = noise(pos.x*stepNoiseXY, pos.y*stepNoiseXY, noiseZ);

      n = map(n, .1, .9, 0, TP);

      speed.x = .3*n*cos(n * TP) * MAX_PARTICLE_SPEED;

      speed.y = .3*n*sin((1-n) * TP) * MAX_PARTICLE_SPEED;

    }

​

    PVector tmp = origin.get();

    tmp.sub(pos);

    tmp.mult(.1);

    speed.add(tmp);

    pos.add(speed);

​

    poss[count%nbZ] = pos.get();

//    println("- - - - - - - count%nbZ: " + count%nbZ);

​

    beginShape();

    int l = Math.min(nbZ, count), k;

    for (int i = 1; i < l; i ++) {

      k = count >= nbZ ? (count + i) % nbZ : i;

      stroke(i, 180);

//      println("k: " + k);

//      stroke(poss[k].z, 255, 255);

      vertex(poss[k].x, poss[k].y, i);

    }

    endShape();

//    println("- - - - - - - poss[0].x: " + poss[0].x);

  }

}

​

void keyPressed() {

  mode = (mode+1)%2;

}