An Introduction to Verlet.js

Verlet.js, a lightweight JavaScript physics engine by Sub Protocol, simplifies 2D physics simulations for web games and scientific applications. This tutorial explores its core functionalities.

Key Concepts:

• Verlet.js leverages Verlet integration, a numerical method solving Newton's equations of motion for efficient 2D particle simulation.
• The library provides functions for creating and manipulating particles, constraints (distance, angle), and handling collisions using continuous collision detection.
• While primarily 2D, 3D simulation is possible with manual handling of the third dimension.

Setting Up:

1. Download Verlet.js from GitHub.

2. Include it in your HTML using a

3. Add a canvas element to your HTML:

   <code class="language-html"><canvas width="800" height="300" id="canvas"></canvas></code>

Initializing and Rendering:

1. VerletJS()Initialize the 2D world using the

   constructor:

   <code class="language-javascript">var world;
   function initializeWorld() {
      world = new VerletJS(800, 300, document.getElementById("canvas"));
   }</code>

2. frame()Render the world by repeatedly calling draw() (physics calculations) and

   (rendering):

   <code class="language-javascript">var fps = 32;
   function renderWorld() {
      world.frame(16);
      world.draw();
      setTimeout(renderWorld, 1000 / fps);
   }</code>

3. Activate the world on page load:

   <code class="language-javascript">window.addEventListener("load", function() {
      initializeWorld();
      renderWorld();
   });</code>

Adding Objects:

Verlet.js uses particles and constraints to build shapes.

• tire()Shapes (using ):tire(origin, radius, segments, stiffness1, stiffness2) Create simple shapes like triangles and squares.

  defines the shape's origin, radius, number of segments, and constraint stiffness.

  <code class="language-javascript">world.tire(new Vec2(100, 100), 100, 3, 1, 1); // Triangle
  world.tire(new Vec2(100, 100), 100, 4, 1, 1); // Square</code>

• lineSegments()Line Segments (using ):Vec2 Create lines using an array of

  points and stiffness.

  <code class="language-javascript">world.lineSegments([new Vec2(100, 100), new Vec2(150, 150)], 1);</code>

• cloth()Cloths (using ):cloth(origin, width, height, segments, pinned, stiffness) Simulate cloth using

  .

  <code class="language-javascript">world.cloth(new Vec2(100, 100), 200, 200, 10, 3, 1);</code>

• CompositeCustom Shapes (using ):Composite For complex shapes, create a

  object, adding particles and constraints manually.

  <code class="language-javascript">var triangle = new world.Composite();
  // Add particles and constraints...
  world.composites.push(triangle);</code>

• Pins:triangle.pin(index, position) Pin particles to fixed positions using

  .

• Gravity:world.gravity = new Vec2(x, y) Modify the world's gravity using

  .

Further Exploration:

This introduction covers the basics. Explore the Verlet.js GitHub repository for advanced features, examples, and further documentation. Experiment with different particle configurations, constraints, and gravity settings to create dynamic simulations.<script> tag: <pre class="brush:php;toolbar:false"><code class="language-html"><script src="verlet-1.0.0-min.js"></script>

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