p2.js Documentation

To create a physics simulation, you need to instantiate a p2.World, create p2.Body objects, add shapes (like p2.Circle or p2.Plane) to those bodies, and add the bodies to the world. To animate the simulation, call world.step() within an animation loop using a fixed time step.

// Create a physics world, where bodies and constraints live
var world = new p2.World({
    gravity:[0, -9.82]
});

// Create an empty dynamic body
var circleBody = new p2.Body({
    mass: 5,
    position: [0, 10]
});

// Add a circle shape to the body
var circleShape = new p2.Circle({ radius: 1 });
circleBody.addShape(circleShape);

// ...and add the body to the world.
// If we don't add it to the world, it won't be simulated.
world.addBody(circleBody);

// Create an infinite ground plane body
var groundBody = new p2.Body({
    mass: 0 // Setting mass to 0 makes it static
});
var groundShape = new p2.Plane();
groundBody.addShape(groundShape);
world.addBody(groundBody);

// To animate the bodies, we must step the world forward in time, using a fixed time step size.
// The World will run substeps and interpolate automatically for us, to get smooth animation.
var fixedTimeStep = 1 / 60; // seconds
var maxSubSteps = 10; // Max sub steps to catch up with the wall clock
var lastTime;

// Animation loop
function animate(time){
	requestAnimationFrame(animate);

    // Compute elapsed time since last render frame
    var deltaTime = lastTime ? (time - lastTime) / 1000 : 0;

    // Move bodies forward in time
    world.step(fixedTimeStep, deltaTime, maxSubSteps);

    // Render the circle at the current interpolated position
    renderCircleAtPosition(circleBody.interpolatedPosition);

    lastTime = time;
}

// Start the animation loop
requestAnimationFrame(animate);

When instantiating a shape (via a subclass of Shape), you can pass an options object to configure its initial state. Note that Shape is a base class and should not be used directly.

Available Options:

• angle (number): Body-local angle. Defaults to 0.
• collisionGroup (number): Bit mask for the collision group. Defaults to 1.
• collisionMask (number): Bit mask for the collision mask. Defaults to 1.
• collisionResponse (boolean): If true, the shape produces contact forces. If false, the shape will move through other shapes but still trigger contact events. Defaults to true.
• material (Material): Material properties for collisions. Defaults to null (uses world defaults).
• position (array): Body-local position (e.g., [x, y]).
• sensor (boolean): If true, the shape becomes a sensor. Sensors do not generate contact forces but still report contact events. Defaults to false.
• type (number): The shape type (see Shape static constants).