Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <script src="https://anuraghazra.github.io/CanvasFun/src/lib/Vector.js"></script>
<canvas id="c">
              
            
!

CSS

              
                * {
  box-sizing: border-box;
}
body {
  margin: 0;
  padding: 0;
}

              
            
!

JS

              
                let canvas = document.getElementById("c");
let ctx = canvas.getContext("2d");
let CANVAS_WIDTH = window.innerWidth-5;
let CANVAS_HEIGHT = window.innerHeight-5;
canvas.width = CANVAS_WIDTH;
canvas.height = CANVAS_HEIGHT;

class Dot {
  constructor(x, y, vx, vy) {
    this.pos = new Vector(x, y);
    this.oldpos = new Vector(x + (vx||0), y + (vy||0)); // velocity x, y

    this.friction = 0.97;
    this.groundFriction = 0.7;

    this.gravity = new Vector(0, 1);

    this.radius = 5;
    this.color = "#e62a4f";
    this.mass = 1;
  }

  update() {
    let vel = Vector.sub(this.pos, this.oldpos);
    vel.mult(this.friction);

    // if the point touches the ground set groundFriction
    if (this.pos.y >= CANVAS_HEIGHT - this.radius && vel.magSq() > 0.000001) {
      var m = vel.mag();
      vel.x /= m;
      vel.y /= m;
      vel.mult(m * this.groundFriction);
    }
    this.oldpos.setXY(this.pos.x, this.pos.y);
    this.pos.add(vel);
    this.pos.add(this.gravity);
  }

   constrain() {
    if (this.pos.x > CANVAS_WIDTH - this.radius) {
      this.pos.x = CANVAS_WIDTH - this.radius;
    }
    if (this.pos.x < this.radius) {
      this.pos.x = this.radius;
    }
    if (this.pos.y > CANVAS_HEIGHT - this.radius) {
      this.pos.y = CANVAS_HEIGHT - this.radius;
    }
    if (this.pos.y < this.radius) {
      this.pos.y = this.radius;
    }
  };
  
  render(ctx) {
    ctx.beginPath();
    ctx.fillStyle = this.color;
    ctx.arc(this.pos.x, this.pos.y, this.radius, 0, Math.PI * 2);
    ctx.fill();
    ctx.closePath();
  }
}
 
class Stick {
  constructor(p1, p2, length) {
    this.startPoint = p1;
    this.endPoint = p2;
    this.stiffness = 2;
    this.color = '#f5476a';
    // if the length is not given then calculate the distance based on position
    if (!length) {
      this.length = this.startPoint.pos.dist(this.endPoint.pos);
    } else {
      this.length = length;
    }

  }
  
  update() {
    // calculate the distance between two dots
    let dx = this.endPoint.pos.x - this.startPoint.pos.x;
    let dy = this.endPoint.pos.y - this.startPoint.pos.y;
    // pythagoras theorem
    let dist = Math.sqrt(dx * dx + dy * dy);
    // calculate the resting distance betwen the dots
    let diff = (this.length - dist) / dist * this.stiffness;

    // getting the offset of the dots
    let offsetx = dx * diff * 0.5;
    let offsety = dy * diff * 0.5;

    // calculate mass
    let m1 = this.startPoint.mass + this.endPoint.mass;
    let m2 = this.startPoint.mass / m1;
    m1 = this.endPoint.mass / m1;

    // and finally apply the offset with calculated mass
    if (!this.startPoint.pinned) {
      this.startPoint.pos.x -= offsetx * m1;
      this.startPoint.pos.y -= offsety * m1;
    }
    if (!this.endPoint.pinned) {
      this.endPoint.pos.x += offsetx * m2;
      this.endPoint.pos.y += offsety * m2;
    }

  }
  
  render(ctx) {
    ctx.beginPath();
    ctx.strokeStyle = this.color;
    ctx.moveTo(this.startPoint.pos.x, this.startPoint.pos.y);
    ctx.lineTo(this.endPoint.pos.x, this.endPoint.pos.y);
    ctx.stroke();
    ctx.closePath();
  }
}

class Entity {
  constructor(iterations) {
    this.dots = [];
    this.sticks = [];
    this.iterations = iterations || 16;
  }

  addDot(x, y, vx, vy) {
    this.dots.push(new Dot(x, y, vx, vy));
  }

  addStick(p1, p2, length) {
    this.sticks.push(new Stick(this.dots[p1], this.dots[p2], length));
  }

  updatePoints() {
    for (let i = 0; i < this.dots.length; i++) {
      this.dots[i].update();
    }
  }

  updateSticks() {
    for (let i = 0; i < this.sticks.length; i++) {
      this.sticks[i].update();
    }
  }

  updateContrains() {
    for (let i = 0; i < this.dots.length; i++) {
      this.dots[i].constrain();
    }
  }

  renderPoints(ctx) {
    for (let i = 0; i < this.dots.length; i++) {
      this.dots[i].render(ctx);
    }
  }
  renderSticks(ctx) {
    for (let i = 0; i < this.sticks.length; i++) {
      this.sticks[i].render(ctx);
    }
  }

  update(ctx) {

    this.updatePoints();
    for (let j = 0; j < this.iterations; j++) {
      this.updateSticks();
      this.updateContrains();
    }
    this.renderPoints(ctx);
    this.renderSticks(ctx);
  }
}

let box = new Entity(100);
box.addDot(100, 100, (Math.random() - 0.5) * 100.0); //x, y, vx, vy
box.addDot(200, 100);
box.addDot(200, 200);
box.addDot(100, 200);

box.addStick(0, 1);
box.addStick(1, 2);
box.addStick(2, 3);
box.addStick(3, 0);
box.addStick(3, 1);


function animate() {
  ctx.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);

  box.update(ctx);
    

  requestAnimationFrame(animate);
}
animate();

              
            
!
999px

Console