Pairs

  // Pairs - Jim Bumgardner
  
  int startTime;
  float durationS = 2;
  float durationMS = durationS*1000;
  float segDist = 100;
  
  PVector[] coords = new PVector[4];
  float d1,d2;
  
  void setup()
  {
    size(500,500);
    noStroke();
    fill(0);
    smooth();
    background( #ffffff );
    for (int i = 1; i < 4; ++i) {
      coords[i] = new PVector(random(width),random(height));
    }
    for (int i = 1; i < 4; ++i) {
      nextPoint();
    }
    startTime = millis();
    frameRate(24);
    d1 = random(10,50);
    d2 = random(10,50);
  }
  
  void nextPoint()
  {
      coords[0] = coords[3];
      coords[1] = coords[2];
      // reflect about coords[0]
      coords[1].x = coords[0].x - (coords[1].x-coords[0].x);
      coords[1].y = coords[0].y - (coords[1].y-coords[0].y);
      do {
        float a = random(TWO_PI);
        coords[3] = new PVector(random(width),random(height));
      } while (dist(coords[3].x,coords[3].y,width/2,height/2) > width/3);
      float a = random(TWO_PI);
      coords[2] = new PVector(coords[3].x+cos(a)*segDist,coords[3].y+sin(a)*segDist);
      d1 = d2;
      d2 = random(10,50);
  }
  
  void draw()
  {
    fill(50,100,50,20);
    rect(0,0,width,height);
    float r = (millis() - startTime)/durationMS;
    while (r > 1.0) {
      r -= 1.0;
      nextPoint();
      startTime += durationMS;
    }
    float x = bezierPoint(coords[0].x,
                         coords[1].x,  
                         coords[2].x,  
                         coords[3].x,
                         r);  
    float y = bezierPoint(coords[0].y,
                         coords[1].y,  
                         coords[2].y,  
                         coords[3].y,
                         r);  
    float tx = bezierTangent(coords[0].x,
                         coords[1].x,  
                         coords[2].x,  
                         coords[3].x,
                         r);  
    float ty = bezierTangent(coords[0].y,
                         coords[1].y,  
                         coords[2].y,  
                         coords[3].y,
                         r);  
    float a = atan2(ty,tx);
    noStroke();
    
    float d = lerp(d1,d2,r);
    
    if (frameCount % 2 > 0) {
      fill( #ffaaaa );
      ellipse(x+cos(a-PI/2)*d,y+sin(a-PI/2)*d,10,10);
    } else {
      fill( #aaaaff );
      ellipse(x+cos(a+PI/2)*d,y+sin(a+PI/2)*d,10,10);
    }
  }