title: How to implement a ShaderToy shader in three.js?
body: <p>looking for info on how to recreate the ShaderToy parameters iGlobalTime, iChannel etc within threejs. I know that iGlobalTime is the time elapsed since the Shader started, and I think the iChannel stuff is for pulling rgb out of textures, but would appreciate info on how to set these.</p>
  
  <p>edit: have been going through all the shaders that come with three.js examples and think that the answers are all in there somewhere - just have to find the equivalent to e.g. iChannel1 =  a texture input etc.</p>