Particle attractor (Unity)

ParticleAttractor.js

var target : Vector3;
var power = 5.0;
function LateUpdate () {
    var particles = particleEmitter.particles;
    for (var i = 0; i < particles.Length; i++) {
    	var rp = target - particles[i].position;
    	if (rp.magnitude < 0.5) {
            // 近づき過ぎたパーティクルを消す。
            particles[i].energy = 0.0;
    	} else {
            // 加速処理。
            particles[i].velocity += rp * (power / rp.sqrMagnitude * Time.deltaTime);
    	}
    }
    particleEmitter.particles = particles;
}