// The Nature of Code

// The Coding Train / Daniel Shiffman

// https://youtu.be/9IQEM_Ijklg

// https://thecodingtrain.com/learning/nature-of-code/2.3-friction.html

// https://editor.p5js.org/codingtrain/sketches/zcTpMCpA

​

let movers = [];

let mu = 0.1;

​

function setup() {

  createCanvas(600, 400);

  for (let i = 0; i < 10; i++) {

    movers[i] = new Mover(random(width), random(0,100), random(2, 4));

  }

}

​

function draw() {

  background(0);

​

  for (let mover of movers) {

    if (mouseIsPressed) {

      let wind = createVector(0.1, 0);

      drawVector(wind, mover.pos.x, mover.pos.y, color(0, 0, 255), 100);

      mover.applyForce(wind, color(0, 0, 255));

    }

    let gravity = createVector(0, 0.2);

    let weight = p5.Vector.mult(gravity, mover.mass);

    drawVector(weight, mover.pos.x, mover.pos.y, color(255, 100, 150), 100);

​

    mover.applyForce(weight, color(0, 255, 0));

    mover.friction();

    mover.update();

    mover.edges();

    mover.show();

  }

}

​

function drawVector(v, x, y, col, factor) {

  push();

  let arrowsize = 4;

  // Translate to position to render vector

  translate(x, y);

  stroke(col);

  // Call vector heading function to get direction (note that pointing up is a heading of 0) and rotate

  rotate(v.heading());

  // Calculate length of vector & scale it to be bigger or smaller if necessary

  let len = v.mag() * factor;

  // Draw three lines to make an arrow (draw pointing up since we've rotate to the proper direction)

  line(0, 0, len, 0);

  line(len, 0, len - arrowsize, +arrowsize / 2);

  line(len, 0, len - arrowsize, -arrowsize / 2);

  pop();

}