title: Avoiding collision between particles and collider in Unity
body: <p>I have an arbitrarily large number of things shooting particle systems at each other. I want the particles to hit the targets but not the origin objects. Is it possible to either:</p>
  
  <ul>
  <li><p>Use <code>IgnoreCollision</code> between a ParticleSystem and a Collider</p></li>
  <li><p>Define new collision layers at runtime</p></li>
  </ul>
  
  <p>Or is there some sneaky way of solving this I haven't considered?</p>