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# SCNPhysicsCollisionCategory

Default values for a physics body’s [`categoryBitMask`](/documentation/SceneKit/SCNPhysicsBody/categoryBitMask) and [`collisionBitMask`](/documentation/SceneKit/SCNPhysicsBody/collisionBitMask) properties.

```
struct SCNPhysicsCollisionCategory
```

## Overview

You specify contact and collision behaviors by defining your own categories for the kinds of bodies your app simulates and setting the [`categoryBitMask`](/documentation/SceneKit/SCNPhysicsBody/categoryBitMask) and [`collisionBitMask`](/documentation/SceneKit/SCNPhysicsBody/collisionBitMask) properties for each body to determine which kinds of bodies it collides with. Additionally, you can use the [`contactDelegate`](/documentation/SceneKit/SCNPhysicsWorld/contactDelegate) property of the physics world to be notified of collisions between bodies.

For more details and example usage, see [`Defining a Body’s Category and Collisions`](/documentation/SceneKit/SCNPhysicsBody#Defining-a-Bodys-Category-and-Collisions) in the class overview.

## Topics

### Constants

[`SCNPhysicsCollisionCategoryDefault`](/documentation/SceneKit/SCNPhysicsCollisionCategory/default)

The default [`categoryBitMask`](/documentation/SceneKit/SCNPhysicsBody/categoryBitMask) value for dynamic and kinematic bodies.

[`SCNPhysicsCollisionCategoryStatic`](/documentation/SceneKit/SCNPhysicsCollisionCategory/static)

The default [`categoryBitMask`](/documentation/SceneKit/SCNPhysicsBody/categoryBitMask) value for static bodies.

[`SCNPhysicsCollisionCategoryAll`](/documentation/SceneKit/SCNPhysicsCollisionCategory/all)

This is the default value for a physics body’s [`collisionBitMask`](/documentation/SceneKit/SCNPhysicsBody/collisionBitMask) property.

## Relationships

### Conforms To

[`RawRepresentable`](/documentation/Swift/RawRepresentable)

[`Equatable`](/documentation/Swift/Equatable)

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`Sendable`](/documentation/Swift/Sendable)

[`BitwiseCopyable`](/documentation/Swift/BitwiseCopyable)

[`SetAlgebra`](/documentation/Swift/SetAlgebra)

[`OptionSet`](/documentation/Swift/OptionSet)

[`ExpressibleByArrayLiteral`](/documentation/Swift/ExpressibleByArrayLiteral)

---

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