gridwalkers gws;
int numgw;
float sc1, sc2, sc3, sc4, t1, t2, t3, t4, cmin, cmax, zrange;
float sr=1.f;
int[] bkg;

void setup(){
  size(680,680);
  bkg=new int[width*height];
  smooth();
  //hint(NO_DEPTH_TEST);
  background(120);
  calculateBackground();
  drawBackground();
  numgw=50;
  sc1=1.f;
  sc2=7.f;
  sc3=13.f;
  sc4=37.f;
  t1=t2=t3=t4=PI/18.0f/sr;
  cmin=1.f;
  cmax=1.f;
  zrange=250.0f/sr;
  gws=new gridwalkers(width, height, numgw);
}

void draw(){
  for(int f=0;f<5;f++){
    gws.update();
  }
  //drawFrame();


}

void calculateBackground(){
  int c;
  for(int i=0; i<width;i++){
    for(int j=0; j<height;j++){
      
      bkg[i+j*width]=color(0);
    }
  }
  for(int i=20; i<width-20;i++){
    for(int j=20; j<height-20;j++){
      c=120+int(135.0f*(float)Math.exp(-10.0*sr*dist(i,j,width/2,height/2)/width));
      bkg[i+j*width]=color(c,c,c);
    }
  } 
}

void drawBackground(){
  loadPixels();
  for(int i=0; i<height*width;i++){
    pixels[i]=bkg[i];
  }
  updatePixels();
}

void drawFrame(){
  noStroke();
  fill(0);
  rect(0,0,680,20);
  rect(0,660,880,680);
  rect(0,20,20,660);
  rect(860,20,880,660);
}

void mouseReleased(){
  background(120);
  drawBackground();
  gws.newGridwalkers();
}

class gridwalkers{
  gridwalker[] gw;
  int w,h,numgw;
  int[][] grid;
  float lx, ly;

  gridwalkers(){
  }

  gridwalkers(int ww, int hh, int nn){
    w=ww;
    h=hh;
    numgw=nn;
    newGridwalkers();
  }

  void newGridwalkers(){
    lx =w/2.0f;
    ly =h/2.0f;
    gw = new gridwalker[numgw];
    grid = new int[w][h];
    for (int i=0;i<numgw;i++){
      gw[i] = new gridwalker(w,h,i+1);
    }
    for (int i=0;i<w;i++){
      for (int j=0;j<h;j++){
        grid[i][j] = -1;
      }
    }

  }

  void update(){
    float d, dprox, ddist,r;
    int g;
    for (int i=0;i<numgw;i++){
      g=grid[int(gw[i].cx)][int(gw[i].cy)];
      d=dist(gw[i].cx,gw[i].cy, gw[i].cz,lx,ly,0);
      dprox=(d-1.0f/sr)/d;
      ddist=(d+1.0f/sr)/d;
      r=0.85*4.0/sr*(0.1+(float)Math.exp(-gw[i].run/50.0));
      if((g>-1)&&(g!=i)){
        gw[i].reset();
      }
      else{
        grid[int(gw[i].cx)][int(gw[i].cy)]=i;
        stroke(255,0,0,200);
        /*if ((pixels[int(gw[i].cx)+int(gw[i].cy)*width]<bkg[int(gw[i].cx)+int(gw[i].cy)*width]+255)&&(pixels[int(gw[i].cx)+int(gw[i].cy)*width]>bkg[int(gw[i].cx)+int(gw[i].cy)*width]-255))*/ point(gw[i].cx,gw[i].cy);
        pushMatrix();
        translate(0,0);//,gw[i].cz);
        noStroke();
        fill(200+int(55.0f*(float)Math.exp(-6.0*sr*d/w)),60*(300-gw[i].cz)/300);
        ellipse(lx+(gw[i].cx-lx)*dprox,ly+(gw[i].cy-ly)*dprox,r,r);
        fill(int(200.0f*(float)Math.exp(-6.0*sr*d/w)),60*(300-gw[i].cz)/300);
        ellipse(lx+(gw[i].cx-lx)*ddist,ly+(gw[i].cy-ly)*ddist,r,r);
        fill(int(255.0f*(float)Math.exp(-6.0*sr*d/w)),int(255.0f*(float)Math.exp(-6.0*sr*d/w)),int(255.0f*(float)Math.exp(-6.0*sr*d/w)),180*(300-gw[i].cz)/300);
        ellipse(gw[i].cx,gw[i].cy,r,r);
        popMatrix();
        stroke(60,10);
        //if ((gw[i].cz<-50)&&(d>50)) line(gw[i].cx,gw[i].cy,gw[i].cz,gw[i].cx+(gw[i].cx-w/2)*(2*w-d)/d,gw[i].cy+(gw[i].cy-h/2)*(2*w-d)/d,gw[i].cz+gw[i].cz*(2*w-d)/d);
                if ((gw[i].cz<-50)&&(d>50)) line(gw[i].cx,gw[i].cy,gw[i].cx+(gw[i].cx-w/2)*(2*w-d)/d,gw[i].cy+(gw[i].cy-h/2)*(2*w-d)/d);

      }
      gw[i].update(1.0f/sr*(1.0f-(float)Math.exp(-10.0*sr*d/w) ));
    }
  }
}

class gridwalker{
  int w,h;
  float cx,cy,cz,dir, dirchange;
  int age;
  float m1,m2,m3,m4;
  float p1,p2,p3,p4;
  float curvature;
  int index;
  int run;

  gridwalker(){
    w=h=age=run=index=0;
    cx=cy=cz=dir=dirchange=m1=m2=m3=m4=p1=p2=p3=p4=curvature=0.0f;
  }

  gridwalker(int ww, int hh, int i){
    index=i;
    run=0;
    w=ww;
    h=hh;
    init();
  }

  void init(){
    cx=int(random(w));
    cy=int(random(h));
    cz=random(-zrange,0);
    dir=random(TWO_PI);
    dirchange=0;
    age=0;
    m1=random(-1.0f,1.0f)*t1;
    m2=random(-1.0f,1.0f)*t2;
    m3=random(-1.0f,1.0f)*t3;
    m4=random(-1.0f,1.0f)*t4;
    p1=random(-PI,PI);
    p2=random(-PI,PI);
    p3=random(-PI,PI);
    p4=random(-PI,PI);
    curvature=random(cmin,cmax);
  }

  void update(float d){
    cx+=d*cos(dir);
    cy+=d*sin(dir);
    if(random(1.0)<curvature){
      dirchange=m1*sin(p1+0.f/sc1*age)+m2*sin(p2+0.1f/sc2*age)+m3*sin(p3+0.1f/sc3*age)+m4*sin(p4+0.1f/sc4*age);
      dir+=dirchange;
    }
    age++;
    check();
    if (cz>0) cz-=0.1;
    if (cz<0) cz+=0.1;
  }

  void check(){
    if (cx<0) cx+=w;
    if (cx>=w) cx-=w;
    if (cy<0) cy+=h;
    if (cy>=h) cy-=h;
  }

    void reset(){
    index+=numgw;
    run+=1;
    init();
  }

}