title: Three.js - Buffer geometry particles, need to animate random groups of particles in system
body: <p>I have a <code>PointCloud</code> with a large number ( 200K+ ) of particles. This <code>PointCloud</code> is constructed using <code>THREE.BufferGeometry</code>, with each vertices position set using <code>Float32Array( numParticles * 3 )</code>. </p>
  
  <p>I would like to animate the <code>x,y</code> positions of randomly selected clusters of particles every <code>n</code> number of seconds. This process needs to be as efficient as possible — so looping though all the particles in the <code>update()</code> and selecting random clusters to animate, is too computationally expensive. </p>
  
  <p>Is there a better way to achieve something like this in <code>Three.js</code> ?</p>