球状でのパーティクルの軌跡

/**
* track on sphere
*
* @author aa_debdeb
* @date 2016/04/19
*/

float radious = 250;
ArrayList<Particle> particles;
PVector rNoise1, rNoise2;
float nScale = 3.4;
float maxVel = PI / 2048;
float velStep = PI / 20480;

void setup(){
  size(640, 640, P3D);
  
  particles = new ArrayList<Particle>();
  for(int i = 0; i < 30; i++){
    particles.add(new Particle());
  }
  rNoise1 = new PVector(random(100000), random(100000));
  rNoise2 = new PVector(random(100000), random(100000));
  
  stroke(0, 128);
  noFill();
}

void draw(){
  background(255);
  translate(width / 2, height / 2);
  rotateX(0.001 * frameCount);
  rotateY(0.002 * frameCount);
  rotateZ(0.003 * frameCount);
  for(Particle particle: particles){
    particle.update();
    particle.draw();
  }
}

class Particle{
  
  float r1, r2;
  float vr1, vr2;
  ArrayList<PVector> track;
  
  Particle(){
    r1 = random(TWO_PI);
    r2 = random(TWO_PI);
    vr1 = random(-maxVel, maxVel);
    vr2 = random(-maxVel, maxVel);
    track = new ArrayList<PVector>();
    float x = radious * sin(r1) * cos(r2);
    float y = radious * sin(r1) * sin(r2);
    float z = radious * cos(r1);
    track.add(new PVector(x, y, z));
  }
  
  void update(){
    vr1 +=  map(noise(rNoise1.x + cos(r1) * nScale, rNoise1.y + sin(r1) * nScale), 0, 1, -velStep, velStep);
    constrain(vr1, -maxVel, maxVel);
    r1 += vr1;
    if(r1 < 0){
      r1 += TWO_PI;
    } else if(r1 >= TWO_PI){
      r1 -= TWO_PI;
    }
    vr2 += map(noise(rNoise2.x + cos(r2) * nScale, rNoise2.y + sin(r2) * nScale), 0, 1, -velStep, velStep);
    constrain(vr2, -maxVel, maxVel);
    r2 += vr2;
    if(r2 < 0){
      r2 += TWO_PI;
    } else if(r2 >= TWO_PI){
      r2 -= TWO_PI;
    }

    float x = radious * sin(r1) * cos(r2);
    float y = radious * sin(r1) * sin(r2);
    float z = radious * cos(r1);
    track.add(new PVector(x, y, z));
    if(track.size() > 1000){
      track.remove(0);
    }
  }
  
  void draw(){
    beginShape();
    for(PVector p: track){
      vertex(p.x, p.y, p.z);
    }
    endShape();
  }
  
}