Ghastly images in Processing

gistfile1.java

void setup()
{
  size(1000, 500);
  verts = new ArrayList<Vertex>();
  
  for(int i=0;i<50;i++) {
    verts.add(new Vertex(random(75, 150)));
  }
  background(bg);
}

class Vertex {
  public PVector x;
  public PVector v;
  public color c;
  public float r;
  public Vertex(float r) {
      this.r = r;
      this.x = new PVector(random(0, width), random(0, height));
      this.v = new PVector(random(-1, 1), random(-1, 1));
      this.c = color(random(255), random(128, 255), 0, 128);
  }
  public void draw() {
    if(showParticles) {
      stroke(this.c);
      fill(this.c);    
      ellipse(x.x, x.y, this.r, this.r);
    }
  }
  public void update() {
    if(x.x < 0 || x.x > width) { v.x = -v.x; }
    if(x.y < 0 || x.y > height) { v.y = -v.y; }
    x.x += v.x;
    x.y += v.y;
  }
  public void lineTo(Vertex o) {
    line(x.x, x.y, o.x.x, o.x.y);
  }
  public double dist(Vertex o) {
    /*return pow(
            pow(x.x - o.x.x, lPMetric) + 
            pow(x.y - o.x.y, lPMetric), invLP);*/
      return x.dist(o.x);
  }
  public List<Vertex> neighbors(ArrayList<Vertex> verts)
  {
    ArrayList<Vertex> opts = new ArrayList<Vertex>();
    for(Vertex v : verts) {
      if(this != v && v.dist(this) < v.r) {
        opts.add(v);
      }
    }
    
    return opts;
  }
  public void affect(Vertex o) {
    PVector d = new PVector(o.x.x, o.x.y);
    d.sub(this.x);
    float m = d.mag();
    d.normalize();
    
    o.v.x += d.x * 50.0 / (m * m);
    o.v.y += d.y * 50.0 / (m * m);
    o.v.x = constrain(o.v.x, -5.0, 5.0);
    o.v.y = constrain(o.v.y, -5.0, 5.0);
  }
}

ArrayList<Vertex> verts; 

boolean isRunning=true;
boolean showParticles=false;
float lPMetric = 2, invLP = 1.0f / 2.0f;
color bg = color(0);

void keyPressed() {
  if(key == 'h') {
    isRunning = !isRunning;
  } else if(key == 'r') {
    background(bg);
  } else if(key == 'p') {
    showParticles = !showParticles;
    background(bg);
  } else if(key >= '0' && key <= '9') {
    lPMetric = (float)(key - '0');
    invLP = 1.0f / lPMetric;
    println("Metric: "+lPMetric);
    background(bg);
  }
}

void draw()
{
  if(isRunning) {
    if(showParticles) {
      background(bg);
    }
    
    for(int i=0;i<verts.size();i++)
    {
      Vertex v = verts.get(i);
      v.draw();
        
      for(Vertex n : v.neighbors(verts)) {
        if(!showParticles) { stroke(random(240,255), 0, 128+128*sin(radians(frameCount * 0.2)), random(3,5)); }
        else { stroke(255, 0, 0); }
      
        v.lineTo(n);
        n.affect(v);
      }
      v.update();
    }
  }
}