The global simulation of collisions, gravity, joints, and other physics effects in a scene.


class SCNPhysicsWorld : NSObject


You do not create SCNPhysicsWorld objects directly; instead, read the physicsWorld property of an SCNScene object. Use physics world object to perform the following tasks:

  • Manage global properties of the simulation, such as its speed and constant gravity. (For more precise control of gravity and similar effects, see the SCNPhysicsField class.)

  • Register behaviors that modify interactions between the scene’s physics bodies, such as joints and vehicles. For more details, see SCNPhysicsBehavior.

  • Specify a delegate object to receive messages when two physics bodies contact each other

  • Perform specific contact tests, and search for physics bodies in the scene using ray and sweep tests.


Managing the Physics Simulation

var gravity: SCNVector3

A vector that specifies the gravitational acceleration applied to physics bodies in the physics world.

var speed: CGFloat

The rate at which the simulation executes.

var timeStep: TimeInterval

The time interval between updates to the physics simulation.

func updateCollisionPairs()

Forces the physics engine to reevaluate possible collisions between physics bodies.

Registering Physics Behaviors

func addBehavior(SCNPhysicsBehavior)

Adds a behavior to the physics world.

func removeBehavior(SCNPhysicsBehavior)

Removes a behavior from the physics world.

var allBehaviors: [SCNPhysicsBehavior]

The list of behaviors affecting bodies in the physics world.

func removeAllBehaviors()

Removes all behaviors affecting bodies in the physics world.

Detecting Contacts Between Physics Bodies

var contactDelegate: SCNPhysicsContactDelegate?

A delegate that is called when two physics bodies come in contact with each other.

func contactTest(with: SCNPhysicsBody, options: [SCNPhysicsWorld.TestOption : Any]? = nil) -> [SCNPhysicsContact]

Checks for contacts between one physics body and any other bodies in the physics world.

Searching for Physics Bodies

Search Options

struct SCNPhysicsWorld.TestOption

Keys in options dictionaries that affect how SceneKit searches for bodies in a collision, ray, or sweep test.


Inherits From

See Also

Physics in a Scene

class SCNPhysicsField

An object that applies forces, such as gravitation, electromagnetism, and turbulence, to physics bodies within a certain area of effect.

class SCNPhysicsBehavior

The abstract superclass for joints, vehicle simulations, and other high-level behaviors that incorporate multiple physics bodies.