noite 4

ArrayList<Body> bodies;
float G;
float mm;//massa do mouse
PVector mouse;
//zA2UYM2s

void setup(){
  fullScreen();
  bodies = new ArrayList();
  for( int i = 0; i < 4; i++ ){
    bodies.add( new Body( random( width ), random( height ), random(2, 8) ) );
  }
  G = 2;
  mm = 25;
  noStroke();
  background(0);
}

void draw(){
  //background(0);
  mouse = new PVector( mouseX, mouseY );
  for( int i = 0; i < bodies.size(); i++ ){
    for( int j = i+1; j < bodies.size(); j++ ){
      bodies.get(i).gravitate( bodies.get(j) );
    }
  }
  for( int i = 0; i < bodies.size(); i++ ) bodies.get(i).run();

}

class Body{
  float mass;
  PVector pos, vel, acc;
  Body(float x, float y, float m){
    mass = m;
    pos = new PVector( x, y );
    //vel = new PVector( random( -2, 2), random(-2, 2) );
    vel = new PVector();
    acc = new PVector();
  }
  void gravitate( Body b ){
    float f = G * (mass * b.mass) / sq( pos.dist(b.pos) );
    float a = atan2( b.pos.y - pos.y, b.pos.x - pos.x );
    acc.add( new PVector( f*cos(a), f*sin(a) ) );
    b.acc.add( new PVector( f*cos(a+PI), f*sin(a+PI) ) );
  }
  void gravitate_to_mouse(){
    float f = G * (mass * mm) / sq( pos.dist(mouse) );
    float a = atan2( mouseY - pos.y, mouseX - pos.x );
    acc.add( new PVector( f*cos(a), f*sin(a) ) );
  }
  void run(){
    //vel.y += 0.005;
    //vel.setMag( 0.99 * vel.mag() );
    gravitate_to_mouse();
    vel.add(acc);
    pos.add(vel);
    ellipse( pos.x, pos.y, mass, mass );
    acc = new PVector();
  }
}
//zA2UYM2s