SCNParticleBirthLocation.volume
New particles can be created at any location within the volume of the emitter shape.
Declaration
case volumeDiscussion
This value applies only when the emitterShape property specifies one of SceneKit’s built-in basic geometries (SCNPlane, SCNBox, SCNSphere, SCNPyramid, SCNCone, SCNCylinder, SCNCapsule, SCNTube, and SCNTorus).