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# SCNParticleSystem.ParticleProperty

Keys identifying properties of individual particles, used by the [`propertyControllers`](/documentation/SceneKit/SCNParticleSystem/propertyControllers) dictionary and the [`handle(_:forProperties:handler:)`](/documentation/SceneKit/SCNParticleSystem/handle(_:forProperties:handler:)) and [`addModifier(forProperties:at:modifier:)`](/documentation/SceneKit/SCNParticleSystem/addModifier(forProperties:at:modifier:)) methods.

```
struct ParticleProperty
```

## Topics

### Type Properties

[`angle`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/angle)

The rotation angle, in radians, of the particle about its axis.

[`angularVelocity`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/angularVelocity)

The particle’s angular velocity (or rate of spin), in radians per second.

[`bounce`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/bounce)

The particle’s restitution coefficient.

[`charge`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/charge)

The particle’s electric charge, in coulombs.

[`color`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/color)

The particle’s tint color, as a vector of red, green, blue, and alpha component values.

[`contactNormal`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/contactNormal)

The normal vector, in scene coordinate space, of a collision between a particle and a geometry in the scene.

[`contactPoint`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/contactPoint)

The location, in scene coordinate space, of a collision between a particle and a geometry in the scene.

[`frame`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/frame)

The current frame index of the particle’s image animation.

[`frameRate`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/frameRate)

The rate, in frames per second, of the particle’s image animation.

[`friction`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/friction)

The particle’s friction coefficient.

[`life`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/life)

The remaining time in the particle’s life span, in seconds.

[`opacity`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/opacity)

The particle’s opacity (or alpha value).

[`position`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/position)

The particle’s position vector in scene coordinate space.

[`rotationAxis`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/rotationAxis)

The particle’s axis of rotation, expressed as a vector in the particle’s local coordinate space.

[`size`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/size)

The width and height of the rendered particle image, in units of scene coordinate space.

[`velocity`](/documentation/SceneKit/SCNParticleSystem/ParticleProperty/velocity)

The particle’s velocity vector in units (of scene coordinate space) per second.


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