// https://cargocollective.com/sagejenson/physarum

​

const positions = [];

const headings = [];

const numParts = 1000;

​

const senseAng = 3.14/16;

const senseRad = 2;

const moveAng = 3.14/32;

const moveRad = 0.1;

const decay = 0.99;

​

function setup() {

  createCanvas(200, 200);

  for(let i = 0; i < numParts; i ++) {

    positions.push(createVector(random(width), random(height)));

    headings.push(random(TWO_PI));

  }

  stroke(255);

  background(0);

}

​

function draw() {

  // Sense, Rotate, Move

  for(let i = 0; i < numParts; i ++) {    

    headings[i] = getHeading(positions[i], headings[i]);

    positions[i].x += cos(headings[i]) * moveRad;

    positions[i].y += sin(headings[i]) * moveRad;

    positions[i].x %= width;

    positions[i].y %= height;

  }

  // Deposite

  for(let i = 0; i < numParts; i ++) {

    const p = positions[i];

    point(p.x, p.y);

  }

  // // Defuse

  // filter(BLUR);

  // Decay

  blendMode(MULTIPLY);

  background(255 * decay);

  blendMode(BLEND);

}

​

function getHeading(pos, heading) {

  const fSensePos = getSensorPos(pos, heading);

  const lSensePos = getSensorPos(pos, heading - senseAng);

  const rSensePos = getSensorPos(pos, heading + senseAng);

  const f = get(fSensePos.x, fSensePos.y);

  const l = get(lSensePos.x, lSensePos.y);

  const r = get(rSensePos.x, rSensePos.y);

  if(f > l && f > r) {

    return heading; // forward is largest, no change

  } else if(f < l && f < r) {

    return heading + (random(1) < 0.5 ? moveAng : -moveAng); // forward smallest, random turn

  } else if(l < r) {

    return heading + moveAng; // right largest, left smallest, turn right

  } else if(r < l) {

    return heading - moveAng; // left largest, right smallest, turn left

  }

  return heading;

}

​

function getSensorPos(pos, angle) {

  const vec = pos.copy();

  vec.x += cos(angle) * senseRad;

  vec.y += sin(angle) * senseRad;

  return vec;

}