<!--
{
  "availability" : [
    "iOS: 8.0.0 - 26.0.0",
    "iPadOS: 8.0.0 - 26.0.0",
    "macCatalyst: 13.1.0 - 26.0.0",
    "macOS: 10.8.0 - 26.0.0",
    "tvOS: 9.0.0 - 26.0.0",
    "visionOS: 1.0.0 - 26.0.0",
    "watchOS: 3.0.0 - 26.0.0"
  ],
  "documentType" : "symbol",
  "framework" : "SceneKit",
  "identifier" : "/documentation/SceneKit/SCNPhysicsWorld/TestOption/backfaceCulling",
  "metadataVersion" : "0.1.0",
  "role" : "Type Property",
  "symbol" : {
    "kind" : "Type Property",
    "modules" : [
      "SceneKit"
    ],
    "preciseIdentifier" : "c:@SCNPhysicsTestBackfaceCullingKey"
  },
  "title" : "backfaceCulling"
}
-->

# backfaceCulling

The key for choosing whether to ignore back-facing polygons in physics shapes when searching for contacts.

```
static let backfaceCulling: SCNPhysicsWorld.TestOption
```

## Discussion

The value for this key is an <doc://com.apple.documentation/documentation/Foundation/NSNumber> object containing a Boolean value. The default value is <doc://com.apple.documentation/documentation/Swift/true>, specifying that the search should only return contacts with the exterior surfaces of any physics shapes. Change the value to <doc://com.apple.documentation/documentation/Swift/false> to consider contacts with both interior and exterior surfaces.

This key applies only to ray and convex sweep tests, and only to physics shapes created using the [`concavePolyhedron`](/documentation/SceneKit/SCNPhysicsShape/ShapeType/concavePolyhedron) option.

---

Copyright &copy; 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)