int maxPoints = 20000;
particle [] points;

int frame = 0;

//int numNodes = 4;
PImage imageA,imageB; 

class particle
{

  float x1,y1,x2,y2,len,angle,mx,my;

  particle()
  {
    x1=0;
    y1=0;
    x2=0;
    y2=0;
  }

}

//float nodeLength[maxNodes];


void setup() { 
  size(400, 400); 

  points = new particle[maxPoints];

  for (int i=0;i<maxPoints;i++)
    points[i] = new particle();


  // Images must be in the "data" directory to load correctly 
  imageA = loadImage("einstein_b.jpg"); 
  imageB = loadImage("monroe_b.jpg");

  preProcess(); 
  noStroke();

  for (int i=0;i<5000000;i++)
  {
    closer((int)(random(1)*(float)(maxPoints-1)), (int)(random(1)*(float)(maxPoints-1)));
  }

  precalc();

  //saveOutput();
} 

void preProcess()
{


  int x=0,y=0;
  color col;
  for (int i=0;i<maxPoints;i++)
  {

    col=0;

    while (red(col)<10.5)
    {
      x = (int)(random(1)*(width-1));
      y = (int)(random(1)*(width-1));
      col = imageA.pixels[x+(y*width)];
    }

    points[i].x1 = x;
    points[i].y1 = y;
    col=0;

    while (red(col)<10.5)
    {
      x = (int)(random(1)*(width-1));
      y = (int)(random(1)*(width-1));
      col = imageB.pixels[x+(y*width)];
    }

    points[i].x2 = x;
    points[i].y2 = y;
  }
}

void saveOutput()
{
  float x,y,l;

  l=0;
  l = (float)mouseX / 400.0;

  for (int j=0;j<=10;j++)
  {
    background(128);
    l = (float)j/20.0f;
    for (int i=0;i<maxPoints-1;i++)
    {
      x = lerp(points[i].x1,points[i].x2,l);
      y = lerp(points[i].y1,points[i].y2,l);
      rect(x,y,1,1);
    }



  }


}






void closer(int p1, int p2)
{
  float da1,da2,db1,db2;

  da1=dist(points[p1].x1,points[p1].y1,points[p1].x2,points[p1].y2);
  db1=dist(points[p2].x1,points[p2].y1,points[p2].x2,points[p2].y2);

  da2=dist(points[p1].x1,points[p1].y1,points[p2].x2,points[p2].y2);
  db2=dist(points[p2].x1,points[p2].y1,points[p1].x2,points[p1].y2);

  if (da2<da1 && db2<db1 )
  {
    float tx,ty;

    tx = points[p2].x2;
    ty = points[p2].y2;

    points[p2].x2 = points[p1].x2;
    points[p2].y2 = points[p1].y2;

    points[p1].x2 = tx;
    points[p1].y2 = ty;
  }

}

void precalc()
{
  float len,w,h,a,mx,my;
  for (int i=0;i<maxPoints-1;i++)
  {
    // rotation method.
    len = dist(points[i].x1,points[i].y1,points[i].x2,points[i].y2) * 0.5f;
    w = points[i].x2 - points[i].x1;
    h = points[i].y2 - points[i].y1;
    a = atan2(w, h);
    mx = (points[i].x2 + points[i].x1)*0.5f;
    my = (points[i].y2 + points[i].y1)*0.5f;

    points[i].angle = a;
    points[i].len = len;
    points[i].mx = mx;
    points[i].my = my;
  }
}

void draw() { 
  //for (int i=0;i<5000;i++)
  {
    //closer((int)(random(1)*(float)(maxPoints-1)), (int)(random(1)*(float)(maxPoints-1)));
  }

  background(128);

  stroke(255);

  //  lerp(a, b, .2);

  float x,y,l;

  l=0;
  l = (float)mouseX / (float)width;



  float xo,yo,len,a,w,h;

  for (int i=0;i<maxPoints-1;i++)
  {

    //points[i].x1 = 100;
    //points[i].y1 = 100;
    //points[i].x2 = 300;
    //points[i].y2 = 300;

    //x = lerp(points[i].x1,points[i].x2,l);
    //y = lerp(points[i].y1,points[i].y2,l);
    //rect(x,y,1,1);


    // rotation method.
    /*
    len = dist(points[i].x1,points[i].y1,points[i].x2,points[i].y2) * 0.5f;
     w = points[i].x2 - points[i].x1;
     h = points[i].y2 - points[i].y1;
     a = atan2(w, h);
     x = (points[i].x1+points[i].x2)*0.5f;
     y = (points[i].y1+points[i].y2)*0.5f;
     xo = sin(a+(2*PI*l)) * len;
     yo = cos(a+(2*PI*l)) * len;
     point(x+xo,y+yo);
     */

    // precalced rotation
    
    len = points[i].len;
     a =  points[i].angle;
     x = points[i].mx;
     y = points[i].my;
     xo = sin(a+(2*PI*l)) * len;
     yo = cos(a+(2*PI*l)) * len;
     point(x+xo,y+yo);
     

  }


/*
  int maxFrames=30;
  if (frame<=maxFrames)
  {

    l = (float)frame/(float)maxFrames;

    for (int i=0;i<maxPoints-1;i++)
    {
      // precalced rotation

      len = points[i].len;
      a =  points[i].angle;
      x = points[i].mx;
      y = points[i].my;
      xo = sin(a+(2*PI*l)) * len;
      yo = cos(a+(2*PI*l)) * len;
      point(x+xo,y+yo);

    }


    //saveFrame("line-####.tif");
    frame++;
  }
*/
}