// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/CodingChallenges/160-spring-forces.html

// https://youtu.be/Rr-5HiXquhw

​

// Simple Spring: https://editor.p5js.org/codingtrain/sketches/dcd6-2mWa

// Spring Vector: https://editor.p5js.org/codingtrain/sketches/_A2pm_SSg

// Spring OOP: https://editor.p5js.org/codingtrain/sketches/9BAoEn4Po

// Soft Spring: https://editor.p5js.org/codingtrain/sketches/S5dY7qjxP

​

let particles = [];

let springs = [];

let spacing = 28;

let cols = 15, rows = 15;

let k = 0.5;

let xoff = 0;

let gravity;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  let startX = width / 2 - (spacing * (cols - 1)) / 2;

  for (let j = 0; j < rows; j++) {

    for (let i = 0; i < cols; i++) {

      particles.push(

        new Particle(1, startX + i * spacing, j * spacing, spacing * 0.5)

      );

      if (i > 0 && j > 0) {

        let a = particles[i + j * cols];

        let b = particles[i - 1 + j * cols];

        let c = particles[i + (j - 1) * cols];

        springs.push(new Spring(k, spacing, a, b));

        springs.push(new Spring(k, spacing, a, c));

      }

      if (i == 0 && j > 0) {

        let a = particles[i + j * cols];

        let b = particles[i + (j - 1) * cols];

        springs.push(new Spring(k, spacing, a, b));

      }

      if (i > 0 && j == 0) {

        let a = particles[i + j * cols];

        let b = particles[i - 1 + j * cols];

        springs.push(new Spring(k, spacing, a, b));

      }

    }

  }

​

  for (let i = 0; i < cols; i++) particles[i].locked = true;

​

  gravity = createVector(0, 0.1);

}

​

function draw() {

  background(255);

  fill(0);

  noStroke();

  textAlign(RIGHT, BOTTOM);

  textSize(16);

  text("framerate: " + nf(frameRate(), 1, 2), width - 5, height - 5);

  stroke(0);

  strokeWeight(2);

  for (let i = springs.length - 1; i >= 0; i--) {

    let s = springs[i];

    s.show();

    s.update();

    if (s.a.position.y > height && s.b.position.y > height) {springs.splice(i, 1);}

    if (mouseIsPressed) {

      let x1 = s.a.position.x;

      let y1 = s.a.position.y;

      let x2 = s.b.position.x;

      let y2 = s.b.position.y;

      if (collideLineCircle(x1, y1, x2, y2, mouseX, mouseY, 10)) {

        springs.splice(i, 1);

      }

    }

  }

  let wind = createVector(0.2*noise(xoff)-0.1,0);

  for (let p of particles) {

    p.applyForce(gravity);

    let drag = p.velocity.copy();

    let speed = drag.mag();

    let dragMag = speed * speed * 0.02;

    drag.normalize().mult(-1).mult(dragMag);

    p.applyForce(drag);

    p.applyForce(wind);

    p.update();

  }

  xoff+=0.01;

}

​