n){
		// randomize the initial position
		position	= position.clone()
		// build mesh
		var material	= new THREE.MeshPhongMaterial({
			map	: texture,
			ambient	: 'cyan'
		})
		var geometry	= new THREE.SphereGeometry(0.5, 16, 32)
		var mesh	= new THREE.Mesh(geometry, material)
		container.add(mesh)

		var maxAge	= 3 + Math.random()*0
		// init opacity
		var age2Opacity	= (function(){
			var tweenFn	= createTweenMidi(maxAge, 0.05*maxAge, 0.3*maxAge)
			return function(age){ return 0.2 + tweenFn(age) * 0.5;	