let tube = SCNCylinder(radius: 0.5, height: 2)
    tube.firstMaterial?.diffuse.contents = UIColor.white
    tube.firstMaterial?.transparency = 0.4
    let nodeTube = SCNNode(geometry: tube)
    nodeTube.position = SCNVector3(0, 0, -3)

    let particleSystem = SCNParticleSystem(named: "FloatingParticleSystem", inDirectory: nil)
    particleSystem?.emitterShape = tube
    particleSystem?.birthLocation = .volume

    nodeTube.addParticleSystem(particleSystem!)
    nodeTube.addChildNode(nodeTube)

    sceneView.scene.rootNode.addChildNode(nodeTube)