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# Emitter Shape

The emission shape is a one, two or three dimensional shape that defines where the emitted particles originate. The shapes are defined by a subset of [`emitterPosition`](/documentation/QuartzCore/CAEmitterLayer/emitterPosition), [`emitterZPosition`](/documentation/QuartzCore/CAEmitterLayer/emitterZPosition), [`emitterSize`](/documentation/QuartzCore/CAEmitterLayer/emitterSize) and [`emitterDepth`](/documentation/QuartzCore/CAEmitterLayer/emitterDepth) properties.

## Topics

### Constants

[`point`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/point)

Particles are emitted from a single point at (`emitterPosition.x`, `emitterPosition.y`, `emitterZPosition`)

[`line`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/line)

Particles are emitted along a line from (`emitterPosition.x - emitterSize.width/2`, `emitterPosition.y`, `emitterZPosition`) to (`emitterPosition.x + emitterSize.width/2`, `emitterPosition.y`, `emitterZPosition`).

[`rectangle`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/rectangle)

Particles are emitted from a rectangle with opposite corners [emitterPosition.x - emitterSize.width/2, emitterPosition.y - emitterSize.height/2, emitterZPosition], [emitterPosition.x + emitterSize.width/2, emitterPosition.y + emitterSize.height/2, emitterZPosition].

[`cuboid`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/cuboid)

Particles are emitted from a cuboid (3D rectangle) with opposite corners: [emitterPosition.x - emitterSize.width/2, emitterPosition.y - emitterSize.height/2, emitterZPosition - emitterDepth/2], [emitterPosition.x + emitterSize.width/2, emitterPosition.y + emitterSize.height/2, emitterZPosition+emitterDepth/2].

[`circle`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/circle)

Particles are emitted from a circle centered at (`emitterPosition.x`, `emitterPosition.y`, `emitterZPosition`) of radius `emitterSize.width`.

[`sphere`](/documentation/QuartzCore/CAEmitterLayerEmitterShape/sphere)

Particles are emitted from a sphere centered at (`emitterPosition.x`, `emitterPosition.y`, `emitterZPosition`) of radius `emitterSize.width`.


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