title: Filtering collisions between particles and bodies in liquidfun
body: <p>I created a functioning JavaScript game using the Box2d framework that LiquidFun provides (and implemented filtering effectively). I understand how to filter using maskBits, categoryBits, and groupIndices.</p>
  
  <p>I've successfully created one particle, but it is colliding with all fixtures. My hope is to filter out some fixtures so that the particle only collides with some fixtures. <strong>What tag is used to handle particle/fixture collisions and filtering?</strong> </p>
  
  <p>The LiquidFun update notes for the 1.0.0 release states <em>"Added option to call a contact listener or filter on particle / fixture or particle / particle interactions."</em> However, I can't find where this was done. </p>
  
  <p>Looking through the source code, <code>b2ContactFilter</code> seemed appropriate, but that looks to handle collisions between two fixtures. Similarly, <code>b2ParticleBodyContact</code>seems pretty appropriate, but I cannot determine how that is supposed to be implemented.</p>