shareDepth between 2 RTs

.js

function shareDepth ( rendertarget1, rendertarget2 ) {

  // to force setup RT1, not for rendering
  renderer.render( new THREE.Scene(), new THREE.Camera(), rendertarget1 );

  // to force setup RT2, not for rendering
  renderer.render( new THREE.Scene(), new THREE.Camera(), rendertarget2 );

  // NOTE
  // To get frame buffer name
  // ```
  // renderer.properties.get( rendertarget1 ).__webglFramebuffer
  // ```
  //
  // To get frame buffer name
  // ```
  // renderer.properties.get( rendertarget1 ).__webglDepthbuffer
  // ```

  var _gl = renderer.context;
  var framebuffer = renderer.properties.get( rendertarget2 ).__webglFramebuffer;
  var renderbufferShareFrom = renderer.properties.get( rendertarget1 ).__webglDepthbuffer;

  _gl.bindFramebuffer( _gl.FRAMEBUFFER, framebuffer );
  _gl.bindRenderbuffer( _gl.RENDERBUFFER, renderbufferShareFrom );

  _gl.framebufferRenderbuffer(
    _gl.FRAMEBUFFER,
    _gl.DEPTH_ATTACHMENT,
    _gl.RENDERBUFFER,
    renderbufferShareFrom
  );

  _gl.bindFramebuffer( _gl.FRAMEBUFFER, null );
  _gl.bindRenderbuffer( _gl.RENDERBUFFER, null );

}