transport network simulation.js

// by gonzalo moiguer www.gonzamoiguer.com.ar
// p5.js sketch
// simulates patterns arising from a transport network
// Based on this 2010 paper by Jeff Jones "Characteristics of pattern formation and evolution in approximations of Physarum transport networks." http://eprints.uwe.ac.uk/15260/1/artl.2010.16.2.pdf
// Also helped by Sage Jenson breakdown and awesome GPU-powered work: https://sagejenson.com/physarum

var mapWidth = 500;
var mapHeight = 500;

var trailMap = [];

var mold = [];
var particleCount = 5000;

//
var particleDepositStrength = 1;
var decaySpeed = 1.01;
var diffusionStrength = 0.1;

var sensorDistance = 1;
var sensorsAngle = 22;
var particleRotationStrength = 27;
//

var showTrailMap = false;
var isSimulating = true;

var diffusion = [
  1/16, 1/8, 1/16, 
  1/8,  1/4, 1/8, 
  1/16, 1/8, 1/16
];


function setup() {
  createCanvas(mapWidth, mapHeight);

  for (let i = 0; i < particleCount; i++) {
    let temp = new Particle();
    mold.push(temp);
  }


  for (let i = 0; i < mapWidth; i++) {
    trailMap[i] = []; // init second dimension
    for (let j = 0; j < mapWidth; j++) {
      trailMap[i][j] = random(0, 0.2);
    }
  }

}

function draw() {
  background(0);

  for (let i = 0; i < mapWidth; i++) {
    for (let j = 0; j < mapWidth; j++) {
      // 5- diffuse
      if (isSimulating) {
        if (i > 1 && i < mapWidth - 2 && j > 1 && j < mapHeight - 2) {
          let suma = 0;
          suma += diffusion[0] * trailMap[i - 1][j - 1];
          suma += diffusion[1] * trailMap[i]    [j - 1];
          suma += diffusion[2] * trailMap[i + 1][j - 1];
          suma += diffusion[3] * trailMap[i - 1][j];
          suma += diffusion[4] * trailMap[i]    [j];
          suma += diffusion[5] * trailMap[i + 1][j]; 
          suma += diffusion[6] * trailMap[i - 1][j + 1];
          suma += diffusion[7] * trailMap[i]    [j + 1];
          suma += diffusion[8] * trailMap[i + 1][j + 1];
          
          trailMap[i][j] = suma;
        }


        // 6- decay
        trailMap[i][j] /= decaySpeed;
      }
      // show
      if (showTrailMap) {
        let color = trailMap[i][j] * 255;
        stroke(color, 0, 0);
        point(i, j);
      }
    }
  }

  noStroke();
  fill(255, 255, 255, 25);
  for (let i = 0; i < mold.length; i++) {
    if (!mold[i].alive) continue;

    if (isSimulating) {
      mold[i].tick();
      mold[i].show();
    }

  }
}

function keyPressed() {
  if (isSimulating) {
    showTrailMap = true;
    isSimulating = false;
  } else {
    showTrailMap = false;
    isSimulating = true;
  }

}


function Particle() {
  this.alive = true;

  this.pos = createVector(random(50, mapWidth - 50), random(50, mapHeight - 50));
  //this.pos  = createVector(width/2,height/2);
  //this.acceleration = createVector(0,0)
  this.speed = random(0.5, 1.5);
  this.maxspeed = 4;
  //this.maxforce = 0.1;
  this.heading = random();


  this.show = function() {
    //point(this.pos.x, this.pos.y); 
    ellipse(this.pos.x, this.pos.y, 3);
  }

  this.tick = function() {
    if (!this.alive) return;
    // 1- sense
    this.maxSense = 0;
    this.maxSenseDir = 0;
    //left
    let radAngle = radians(this.heading - sensorsAngle);
    let sensorX = round(this.pos.x + (sensorDistance * cos(radAngle)));
    let sensorY = round(this.pos.y + (sensorDistance * sin(radAngle)));
    let sensorRead = trailMap[constrain(sensorY, 0, mapWidth - 1)][constrain(sensorX, 0, mapHeight - 1)];
    if (sensorRead > this.maxSense) {
      this.maxSense = sensorRead;
      this.maxSenseDir = -1;
    }
    // center
    radAngle = radians(this.heading);
    sensorX = round(this.pos.x + (sensorDistance * cos(radAngle)));
    sensorY = round(this.pos.y + (sensorDistance * sin(radAngle)));
    sensorRead = trailMap[constrain(sensorY, 0, mapWidth - 1)][constrain(sensorX, 0, mapHeight - 1)];
    if (sensorRead >= this.maxSense) {
      this.maxSense = sensorRead;
      this.maxSenseDir = 0;
    }
    // right
    radAngle = radians(this.heading + sensorsAngle);
    sensorX = round(this.pos.x + (sensorDistance * cos(radAngle)));
    sensorY = round(this.pos.y + (sensorDistance * sin(radAngle)));
    sensorRead = trailMap[constrain(sensorY, 0, mapWidth - 1)][constrain(sensorX, 0, mapHeight - 1)];
    if (sensorRead > this.maxSense) {
      this.maxSense = sensorRead;
      this.maxSenseDir = 1;
    }

    // 2- rotate
    this.heading += particleRotationStrength * this.maxSenseDir;

    // 3- move
    radAngle = radians(this.heading);
    this.pos.x += this.speed * cos(radAngle);
    this.pos.y += this.speed * sin(radAngle);

    // collision dead
    if (this.pos.x <= 0 || this.pos.x >= mapWidth || this.pos.y <= 0 || this.pos.y >= mapHeight) {
      this.alive = false;
    }

    // 4- deposit material
    if (this.alive) {
      trailMap[constrain(round(this.pos.x), 0, mapWidth - 1)]
        [constrain(round(this.pos.y), 0, mapHeight - 1)] += particleDepositStrength;
    } else {
      trailMap[constrain(round(this.pos.x), 0, mapWidth - 1)]
        [constrain(round(this.pos.y), 0, mapHeight - 1)] = 0; // les aviso que todo mal
    }

  }

  /*
   this.seek = function(target) {
    this.desired = p5.Vector.sub(target, this.pos);
    this.desired.normalize();
    this.desired.mult(this.maxspeed);
    this.steer = p5.Vector.sub(this.desired,this.velocity);
    this.steer.limit(this.maxforce);
    applyForce(steer);
  }
  
  this.applyForce = function(force) {
    this.acceleration.add(force);
  }
  */

}


function mousePressed() {
  for (let i = 0; i < mapWidth; i++) {
    for (let j = 0; j < mapWidth; j++) {
      if (dist(i, j, mouseX, mouseY) < 10) {
        trailMap[i][j] = 99900;
      }

    }
  }

}