In animated modes, this determines how quickly the particle emission position moves across the Mesh.
The value is specified in terms of the number of complete passes over the Mesh. A value of 2 would mean that the particle emission position traversed the Mesh twice per second. See Also: ParticleSystem.ShapeModule.meshSpawnMode, ParticleSystemShapeMultiModeValue, ParticleSystem.ShapeModule.shapeType.