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# fieldBitMask

A mask that defines which categories of physics fields can exert forces on this physics body.

```
var fieldBitMask: UInt32 { get set }
```

## Discussion

When a physics body is inside the region of an [`SKFieldNode`](/documentation/SpriteKit/SKFieldNode) object, that field node’s [`categoryBitMask`](/documentation/SpriteKit/SKFieldNode/categoryBitMask) property is compared to this physics body’s [`fieldBitMask`](/documentation/SpriteKit/SKPhysicsBody/fieldBitMask) property by performing a logical AND operation. If the result is a nonzero value, the field node’s effect is applied to the physics body.

The default value is `0xFFFFFFFF` (all bits set).

---

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