# PhysicsBodyComponent A component that defines an entity’s behavior in physics body simulations. ``` struct PhysicsBodyComponent ``` ## Overview Only entities with a [`PhysicsBodyComponent`](/documentation/RealityKit/PhysicsBodyComponent) and a [`CollisionComponent`](/documentation/RealityKit/CollisionComponent) can participate in a scene’s physics simulation. If you need to move an entity that participates in the physics system, it also needs a [`PhysicsMotionComponent`](/documentation/RealityKit/PhysicsMotionComponent). Add a physics body component to an entity by adopting the [`HasPhysicsBody`](/documentation/RealityKit/HasPhysicsBody) protocol, which allows RealityKit’s physics simulation to compute behavior in response to forces acting upon the body, following basic rules of Newtonian mechanics. Note the following when considering applying a non-uniform scale to an entity: - Non-uniform scaling is applicable only to box, convex mesh and triangle mesh collision shapes. - Non-uniform scaling is not supported for all other types of collision shapes. In this case the scale.x value is duplicated to the scale’s y and z components as well to force scale uniformity based on the x component. - If the entity has a non-uniform scale assigned to its transform then that entity should not have any descendants assigned that contain rotations in their transforms. A good rule of thumb is to assign the non-uniform scale to the entity that has the collision shape, and avoid adding children below that entity. > Note: Model entities have a physics body component by default. ## Topics ### Creating a physics body component [`init()`](/documentation/RealityKit/PhysicsBodyComponent/init()) Creates a physics body component with default settings. [`init(massProperties:material:mode:)`](/documentation/RealityKit/PhysicsBodyComponent/init(massProperties:material:mode:)) Creates a physics body component with the given mass properties, material, and mode. [`init(shapes:density:material:mode:)`](/documentation/RealityKit/PhysicsBodyComponent/init(shapes:density:material:mode:)) Creates a physics body component deriving mass properties from shape and density. [`init(shapes:mass:material:mode:)`](/documentation/RealityKit/PhysicsBodyComponent/init(shapes:mass:material:mode:)) Creates a physics body component deriving mass properties from shape and mass. ### Detecting collisions [`isContinuousCollisionDetectionEnabled`](/documentation/RealityKit/PhysicsBodyComponent/isContinuousCollisionDetectionEnabled) A Boolean that controls whether the physics simulation performs continuous collision detection. ### Locking movement [`isRotationLocked`](/documentation/RealityKit/PhysicsBodyComponent/isRotationLocked) A tuple of Boolean values that you use to lock rotation of the physics body around any of the three axes. [`isTranslationLocked`](/documentation/RealityKit/PhysicsBodyComponent/isTranslationLocked) A tuple of Boolean values that you use to lock the position of the physics body along any of the three axes. ### Setting the mode [`mode`](/documentation/RealityKit/PhysicsBodyComponent/mode) The behavioral mode that controls the way the physics body moves and interacts with other physics bodies in a simulation. ### Setting material properties [`material`](/documentation/RealityKit/PhysicsBodyComponent/material) The physics body’s material properties, like friction. ### Setting mass properties [`massProperties`](/documentation/RealityKit/PhysicsBodyComponent/massProperties) The physics body’s mass properties, like inertia and center of mass. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)