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# SCNPhysicsContact

Detailed information about a contact between two physics bodies in a scene’s physics simulation.

```
class SCNPhysicsContact
```

## Overview

You don’t create  [`SCNPhysicsContact`](/documentation/SceneKit/SCNPhysicsContact) instances directly; SceneKit automatically creates these objects whenever contacts occur.

To receive contact messages, assign your custom class implementing the [`SCNPhysicsContactDelegate`](/documentation/SceneKit/SCNPhysicsContactDelegate) protocol to the [`contactDelegate`](/documentation/SceneKit/SCNPhysicsWorld/contactDelegate) property of your scene’s [`SCNPhysicsWorld`](/documentation/SceneKit/SCNPhysicsWorld) obejct. Next, for each physics body in your scene, set the [`categoryBitMask`](/documentation/SceneKit/SCNPhysicsBody/categoryBitMask) and [`collisionBitMask`](/documentation/SceneKit/SCNPhysicsBody/collisionBitMask) properties to define which interactions should generate contact messages.

## Topics

### Inspecting the Contact Properties

[`nodeA`](/documentation/SceneKit/SCNPhysicsContact/nodeA)

The node containing the first body in the contact.

[`nodeB`](/documentation/SceneKit/SCNPhysicsContact/nodeB)

The node containing the second body in the contact.

[`contactPoint`](/documentation/SceneKit/SCNPhysicsContact/contactPoint)

The contact point between the two physics bodies, in scene coordinates.

[`contactNormal`](/documentation/SceneKit/SCNPhysicsContact/contactNormal)

The normal vector at the contact point between the two physics bodies, in scene coordinates.

[`collisionImpulse`](/documentation/SceneKit/SCNPhysicsContact/collisionImpulse)

The force over time of the collision, in newton-seconds.

[`penetrationDistance`](/documentation/SceneKit/SCNPhysicsContact/penetrationDistance)

The distance of overlap, in units of scene coordinate space, between the two physics bodies.

## Relationships

### Conforms To

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

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

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

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

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

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

### Inherits From

[`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class)

---

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