# continuousCollisionDetectionThreshold The minimum distance the body must travel for SceneKit to apply a more precise (but more costly) algorithm to detect contacts with other bodies. ``` var continuousCollisionDetectionThreshold: CGFloat { get set } ``` ## Discussion SceneKit’s physics engine can employ two kinds of collision detection: - With *discrete* collision detection, when SceneKit simulates physics before rendering each frame (see [`timeStep`](/documentation/SceneKit/SCNPhysicsWorld/timeStep) and [`SCNSceneRendererDelegate`](/documentation/SceneKit/SCNSceneRendererDelegate)), it updates the position of each physics body based on the body’s velocity during that time interval, then checks to see whether the body at its new position intersects other bodies. - With *continuous* collision detection, SceneKit calculates the volume that will be traversed by a body during each frame, then checks to see whether that volume intersects other bodies. This property’s value defaults to `0.0`, resulting in discrete collision detection at all times. When this value is nonzero, SceneKit applies continuous collision whenever the body travels more than the specified distance within one [`timeStep`](/documentation/SceneKit/SCNPhysicsWorld/timeStep). Discrete collision detection offers high performance, but can lead to inaccurate results for small, fast-moving bodies. Continuous collision detection has a performance cost and works only for spherical physics shapes, but provides more accurate results. For example, in a game involving projectiles and targets, a small projectile may pass through a target if it moves farther than the target’s thickness within one time step. By setting the projectile’s [`continuousCollisionDetectionThreshold`](/documentation/SceneKit/SCNPhysicsBody/continuousCollisionDetectionThreshold) to match its diameter, you ensure that SceneKit always detects collisions between the projectile and other objects. --- 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)