davies-rogers.js

// Run this in https://editor.p5js.org/

// https://qiita.com/aa_debdeb/items/e416ae8a018692fc07eb
function randomOnSphere() {
  const cosTheta = -2.0 * Math.random() + 1.0;
  const sinTheta = Math.sqrt(1.0 - cosTheta * cosTheta);
  const phi = 2.0 * Math.PI * Math.random();
  return [
    sinTheta * Math.cos(phi),
    sinTheta * Math.sin(phi),
    cosTheta
  ];
}

function setup() {
  createCanvas(700, 700, WEBGL);
  noLoop();  
}

function draw() {
  camera(0, 0, 300, 0, 0, 0, 0, 1, 0);
  lights();
  background(255);
  stroke("black");
  strokeWeight(0.01);
  let positions = [];
  const N = 500;
  for(let i = 0; i < N; i++) {
    const pos = randomOnSphere();
    positions.push(pos);
  }
  for(let i = 0; i < N; i++) {
    for(let j = 0; j < i; j++) {
      let p = positions[i], q = positions[j];
      if (dist(p[0], p[1], p[2], q[0], q[1], q[2]) >= 2 - 1 / 8) {
        line(100.0 * p[0], 100.0 * p[1], 100.0 * p[2], 100.0 * q[0], 100.0 * q[1], 100.0 * q[2]);
      }
    }
  }
  noStroke();
  for(let i = 0; i < N; i++) {
    push();
    translate(100.0 * positions[i][0], 100.0 * positions[i][1], 100.0 * positions[i][2]);
    sphere(2.0);
    pop();
  }
}