---
title: birthRate
framework: scenekit
role: symbol
role_heading: Instance Property
path: scenekit/scnparticlesystem/birthrate
---

# birthRate

The number of particles spawned during each emission period. Animatable.

## Declaration

```swift
var birthRate: CGFloat { get set }
```

## Discussion

Discussion The system emits this number of particles at a constant rate through the duration of the period specified by the emissionDuration property. A value of zero prevents the system from emitting particles, unless you randomize the birth rate with the birthRateVariation property. The default value is 1. You can animate changes to this property’s value. See Animating SceneKit Content.

## See Also

### Managing Particle Emission Timing

- [emissionDuration](scenekit/scnparticlesystem/emissionduration.md)
- [emissionDurationVariation](scenekit/scnparticlesystem/emissiondurationvariation.md)
- [idleDuration](scenekit/scnparticlesystem/idleduration.md)
- [idleDurationVariation](scenekit/scnparticlesystem/idledurationvariation.md)
- [loops](scenekit/scnparticlesystem/loops.md)
- [warmupDuration](scenekit/scnparticlesystem/warmupduration.md)
- [birthRateVariation](scenekit/scnparticlesystem/birthratevariation.md)