# PortalComponent.Volume A box-shaped region in portal-local space that defines a volumetric portal boundary. ``` struct Volume ``` ## Overview Pair this type with [`PortalComponent.ClippingMode.volume(_:)`](/documentation/RealityKit/PortalComponent/ClippingMode-swift.enum/volume(_:)) to clip portal world content to a box, or with [`PortalComponent.CrossingMode.volume(_:)`](/documentation/RealityKit/PortalComponent/CrossingMode-swift.enum/volume(_:)) to allow crossing entities to pass through the box’s faces. [`PortalComponent.Volume`](/documentation/RealityKit/PortalComponent/Volume) describes an axis-aligned box in the portal entity’s local coordinate space. The box is centered at [`position`](/documentation/RealityKit/PortalComponent/Volume/position) and spans the full lengths given by [`extents`](/documentation/RealityKit/PortalComponent/Volume/extents) along each axis. [`extents`](/documentation/RealityKit/PortalComponent/Volume/extents) are full extents, not half-extents — a volume with `extents = [1, 1, 1]` is a one-cubic-meter box. For typical room-sized portals where the box should enclose the portal surface, prefer [`enclosingBox(depth:)`](/documentation/RealityKit/PortalComponent/BoundaryStyle/enclosingBox(depth:)), which derives the X and Y extents from the portal’s [`PortalComponent.SurfaceStyle`](/documentation/RealityKit/PortalComponent/SurfaceStyle) for you. ## Topics ### Creating a volume [`init(position: SIMD3, extents: SIMD3)`](/documentation/RealityKit/PortalComponent/Volume/init(position:extents:)) Creates a volume with the given center position and extents. ### Configuring the extents [`var extents: SIMD3`](/documentation/RealityKit/PortalComponent/Volume/extents) The full lengths of the volume along the X, Y, and Z axes of portal-local space, in meters. ### Instance Properties [`var position: SIMD3`](/documentation/RealityKit/PortalComponent/Volume/position) The center of the volume in portal-local space, in meters. ## Relationships ### Conforms To [`Equatable`](/documentation/Swift/Equatable) --- 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)