---
title: contactTestBitMask
framework: scenekit
role: symbol
role_heading: Instance Property
path: scenekit/scnphysicsbody/contacttestbitmask
---

# contactTestBitMask

A mask that defines which categories of bodies cause intersection notifications with this physics body.

## Declaration

```swift
var contactTestBitMask: Int { get set }
```

## Discussion

Discussion When two physics bodies overlap, a contact may occur. SceneKit compares the body’s contact mask to the other body’s category mask by performing a bitwise AND operation. If the result is a nonzero value, SceneKit creates an SCNPhysicsContact object describing the contact and sends messages to the  contactDelegate object of the scene’s physics world. For best performance, only set bits in the contact mask for interactions you are interested in. For applications running in OS X v10.10 or iOS 8, this property’s value matches that of the collisionBitMask property—that is, SceneKit sends contact messages if and only if a collision occurs. For applications running in OS X v10.11 or iOS 9 or later, this property’s value defaults to zero and need not match the collision mask—that is, a pair of bodies generates contact messages whenever the bodies intersect, regardless of whether they collide or pass through one another.

## See Also

### Working with Contacts and Collisions

- [categoryBitMask](scenekit/scnphysicsbody/categorybitmask.md)
- [collisionBitMask](scenekit/scnphysicsbody/collisionbitmask.md)
- [SCNPhysicsCollisionCategory](scenekit/scnphysicscollisioncategory.md)
- [continuousCollisionDetectionThreshold](scenekit/scnphysicsbody/continuouscollisiondetectionthreshold.md)