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].
Declaration
static let cuboid: CAEmitterLayerEmitterShape