let FoV = 200;

let w;

let alpha_min;

let alp, bet;

let dalp = 0;

let dbet = 0;

let speed;

let theta = 0;

​

function setup() {

  createCanvas(2*FoV, 2*FoV);

  w = FoV * 2 / (N - 1);

  alpha_min = -FoV;

  alp = random(-FoV, FoV);

  bet = random(-FoV, FoV);

  speed = document.getElementById("speedslider")

}

​

function draw() {

  theta += (speed.value/100)/60*PI;

//  theta TWO_PI*frameCount*(speed.value/100)/300;

  alp = FoV*cos(theta*1/4)*cos(theta);

  bet = FoV*cos(theta*1/4)*sin(theta);

  background(245);

  push();

  translate(width / 2, height / 2);

  noStroke();

  fill(0, 0, 0);

  for (let mi = 0; mi < N; mi++) {

    for (let ni = 0; ni < N; ni++) {

      ellipse((alpha_min + ni * w), (alpha_min + mi * w), 1 * 20, 1 * 20);

    }

  }

  //text("ρ1",width/2-30,-30)

  //text("ρ2",30,-height/2+30)

  stroke(0);

  line(-width,0,width,0);

  line(0,-height,0,height);

  noStroke();

  let sum = 0;

  for (let mi = 0; mi < N; mi++) {

    let dy = abs(bet - (alpha_min + mi * w)) / w;

    if (dy >= 1) {

      continue;

    }

    for (let ni = 0; ni < N; ni++) {

      let dx = abs(alp - (alpha_min + ni * w)) / w;

      if (dx >= 1) {

        continue;

      }

      let coeff = (1 - dx) * (1 - dy);

      sum += coeff;

      fill(0, 255, 0);

      stroke(0,255,0);

      strokeWeight(5*coeff);

      line((alpha_min + ni * w),(alpha_min + mi * w),alp,bet);

      noStroke();

      ellipse((alpha_min + ni * w), (alpha_min + mi * w), coeff * 20, coeff * 20);

      fill(0);

      text(coeff.toFixed(2),15+(alpha_min + ni * w),15+(alpha_min + mi * w));

    }

  }

  fill(0, 0, 255);

  ellipse(alp, bet, 10, 10);

  pop();

  //text(sum.toFixed(8),20,20);

}