repelAttract

int num = 50, fc;
Mover[ ]movers = new Mover[num];
Attractor a;
float theta;
PFont myFont;
String watermark = "p5art.tumblr.com";
Boolean save = false;

void setup() {
  size(540, 540);
  background(0);
  noCursor();
  myFont = loadFont("PTSans-Caption-12.vlw");
  textFont(myFont);
  for (int i=0; i<movers.length; i++) {
    movers[i] = new Mover(random(0.5, 2), random(width), random(height));
  }
  a = new Attractor();
}

void draw() {
  background(#490A3D);
  fill(255, 100);
  text(watermark, width-textWidth(watermark)-5, height-5);
  a.update();
  a.display();

  for (int i=0; i<movers.length; i++) {
    for (int j=0; j<movers.length; j++) {
      if (i!= j) {
        //PVector force = movers[j].repel(movers[i]);
        PVector force = movers[j].attract(movers[i]);
        movers[i].applyForce(force);
      }
    }
    movers[i].update();
    movers[i].display();
    //movers[i].drawLines();
    movers[i].checkEdges();
  }

  for (int i=0; i<movers.length; i++) {
    //PVector force = a.attract(movers[i]);
    PVector force = a.repel(movers[i]);
    movers[i].applyForce(force);
  }

  if (save) {
    if (frameCount%1==0 && frameCount<fc+120)saveFrame("image-####.gif");
    if (frameCount==fc+120) noLoop();
  }
}

void keyPressed() {
  fc = frameCount;
  save = true;
}

class Attractor {

  float mass;
  PVector location;
  float G;

  Attractor() {
    location = new PVector(width/2, height/2);
    mass = 20;
    G = 40.0;
  }

  void update() {
    location = new PVector(mouseX, mouseY);
  }

  void display() {
    stroke(#ffffff);
    strokeWeight(7);
    fill(#BD1550);
    ellipse(location.x, location.y, mass*2, mass*2);
  }

  PVector attract(Mover m) {
    PVector force = PVector.sub(location, m.location);
    float distance = force.mag();
    distance = constrain(distance, 5.0, 15.0);
    float d = map(distance, 5.0, 15.0, .25, 1.0);
    //d = 1;
    force.normalize();
    float strength = (G*mass*m.mass)/(distance*distance)*d;
    force.mult(strength);

    return force;
  }

  PVector repel(Mover m) {

    PVector force = PVector.sub(location, m.location);
    float distance = force.mag();
    distance = constrain(distance, 5.0, 5000.0);
    force.normalize();

    float strength = (G * mass * m.mass) / (distance * distance)*-1;
    force.mult(strength);
    return force;
  }
}

class Attractor {

  float mass;
  PVector location;
  float G;

  Attractor() {
    location = new PVector(width/2, height/2);
    mass = 20;
    G = 40.0;
  }

  void update() {
    location = new PVector(mouseX, mouseY);
  }

  void display() {
    stroke(#ffffff);
    strokeWeight(7);
    fill(#BD1550);
    ellipse(location.x, location.y, mass*2, mass*2);
  }

  PVector attract(Mover m) {
    PVector force = PVector.sub(location, m.location);
    float distance = force.mag();
    distance = constrain(distance, 5.0, 15.0);
    float d = map(distance, 5.0, 15.0, .25, 1.0);
    //d = 1;
    force.normalize();
    float strength = (G*mass*m.mass)/(distance*distance)*d;
    force.mult(strength);

    return force;
  }

  PVector repel(Mover m) {

    PVector force = PVector.sub(location, m.location);
    float distance = force.mag();
    distance = constrain(distance, 5.0, 5000.0);
    force.normalize();

    float strength = (G * mass * m.mass) / (distance * distance)*-1;
    force.mult(strength);
    return force;
  }
}