# init(type:shape:) Creates a physics body with the specified type and shape. ``` convenience init(type: SCNPhysicsBodyType, shape: SCNPhysicsShape?) ``` ## Parameters `type` A constant that determines how a body responds to forces and collisions. See [`SCNPhysicsBodyType`](/documentation/SceneKit/SCNPhysicsBodyType). `shape` A physics shape defining the volume of the body for collision detection purposes. ## Return Value A new physics body object. ## Discussion For the body to participate in collision detection or respond to forces, you must attach it to the [`physicsBody`](/documentation/SceneKit/SCNNode/physicsBody) property of an [`SCNNode`](/documentation/SceneKit/SCNNode) object in a scene. If you pass `nil` for the shape parameter, SceneKit automatically creates a physics shape for the body when you attach it to a node, based on that node’s [`geometry`](/documentation/SceneKit/SCNNode/geometry) property. To create a physics shape that’s based on the geometries of a node and its hierarchy of children, or to control the level of detail in a physics shape, create the physics shape manually using an [`SCNPhysicsShape`](/documentation/SceneKit/SCNPhysicsShape) class method. > Note: > For nodes containing custom geometry, the physics shape SceneKit automatically creates is a rough approximation of the geometry. This approximation, or *convex hull*, provides a compromise between accuracy and performance in collision detection. For the best collision detection performance, create an ``doc://com.apple.scenekit/documentation/SceneKit/SCNPhysicsShape`` instance based on a basic geometry class (``doc://com.apple.scenekit/documentation/SceneKit/SCNBox``, ``doc://com.apple.scenekit/documentation/SceneKit/SCNSphere``, ``doc://com.apple.scenekit/documentation/SceneKit/SCNPyramid``, ``doc://com.apple.scenekit/documentation/SceneKit/SCNCone``, ``doc://com.apple.scenekit/documentation/SceneKit/SCNCylinder``, or ``doc://com.apple.scenekit/documentation/SceneKit/SCNCapsule``). ## See Also [`type`](/documentation/SceneKit/SCNPhysicsBody/type) A constant that determines how the physics body responds to forces and collisions. [`physicsShape`](/documentation/SceneKit/SCNPhysicsBody/physicsShape) An object that defines the solid volume of the physics body for use in collision detection. --- 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)