threejs-viewer-11

render() {
  // ... other code snippet e.g. this.renderer.render(this.scene, this.camera);

  //don't let renderer erase canvas
  this.renderer.autoClear = false;
  this.renderer.render( this.selectionScene, this.camera );

  //let renderer clean next time
  // (next time is when we render scene1 again)
  this.renderer.autoClear = true;

  // ... other code snippet
}