threejs-viewer-11

render() {
    // put below after 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 (i.e. requestAnimationFrame(this.render.bind(this));)
}