---
title: SCNParticleBirthDirection.surfaceNormal
framework: scenekit
role: symbol
role_heading: Case
path: scenekit/scnparticlebirthdirection/surfacenormal
---

# SCNParticleBirthDirection.surfaceNormal

The emitting direction for each particle is along the surface normal vector at the point where the particle is emitted.

## Declaration

```swift
case surfaceNormal
```

## Discussion

Discussion The particle system creates new particles at points in space defined by the emitterShape geometry. When a new particle is emitted, the geometry’s surface normal vector at the point nearest the particle determines the particle’s initial direction. (Note that the birthLocation property defines where particles may be created relative to the emitterShape geometry.) This value has no effect if the emitterShape property value is nil.

## See Also

### Constants

- [SCNParticleBirthDirection.constant](scenekit/scnparticlebirthdirection/constant.md)
- [SCNParticleBirthDirection.random](scenekit/scnparticlebirthdirection/random.md)