# categoryBitMask A mask that defines which categories the node belongs to. ``` var categoryBitMask: Int { get set } ``` ## Discussion You can assign each node in a scene to one or more categories, where each category corresponds to a bit in the bit mask. You define the mask values used in your app. When SceneKit renders a scene, it compares each node’s [`categoryBitMask`](/documentation/SceneKit/SCNNode/categoryBitMask) property with the category bit masks of every other object that participates in the rendering process—lights, cameras, and techniques—using a bitwise AND operation. If the result is a nonzero value, SceneKit includes the node when rendering. The default category bit mask is `1`. Use a node’s category bit mask together with: - An [`SCNLight`](/documentation/SceneKit/SCNLight) object’s [`categoryBitMask`](/documentation/SceneKit/SCNLight/categoryBitMask) property to exclude the node from that light’s illumination - An [`SCNCamera`](/documentation/SceneKit/SCNCamera) object’s [`categoryBitMask`](/documentation/SceneKit/SCNCamera/categoryBitMask) property to make the node invisible to that camera - The category bit masks in an [`SCNTechnique`](/documentation/SceneKit/SCNTechnique) object’s definition dictionary to include or exclude the node from phases of a multipass rendering technique > Note: > This property doesn’t affect SceneKit’s physics simulation. To include or exclude a node from physics interactions, use the ``doc://com.apple.scenekit/documentation/SceneKit/SCNPhysicsBody/categoryBitMask`` property of the node’s ``doc://com.apple.scenekit/documentation/SceneKit/SCNNode/physicsBody`` and ``doc://com.apple.scenekit/documentation/SceneKit/SCNNode/physicsField`` 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)