birthDirection
The possible initial directions for newly spawned particles, relative to the emitter shape.
Declaration
var birthDirection: SCNParticleBirthDirection { get set }Discussion
This property defines initial directions for new particles relative to the geometry specified in the emitterShape property. This property has no effect if the emitterShape property value is nil.
For example, if the emitter shape is an SCNSphere geometry and the birth location is SCNParticleBirthDirection.surfaceNormal, new particles radiate away from the center of the sphere. You can randomize the direction of newly spawned particles with the spreadingAngle property.
The default value is SCNParticleBirthDirection.constant, specifying that all particles use the same base emittingDirection value. For possible values, see SCNParticleBirthDirection.