title: get transformed vertices positions after vertex shader in THREE.js
body: <p>I am changing the positions of some vertices inside a vertex shader but i can't find a way to get those new updated vertices positions back inside js (i'm currently using THREE.js : the vertex position of my mesh's vertices  always remains the same).
  I found this link <a href="https://stackoverflow.com/questions/29053870/retrieve-vertices-data-in-three-js">Retrieve Vertices Data in THREE.js</a>, but glGetTexImage doesn't exist in webgl (and i'm quite skeptical about this floating-point texture method as well).
  Thanks for your help !</p>