Вот ответ ...
function onDocumentMouseMove( event ) {
event.preventDefault();
mouse2D.x = ( event.clientX / window.innerWidth ) * 2 - 1;
mouse2D.y = - ( event.clientY / window.innerHeight ) * 2 + 1;
}
function render() {
mouse3D = projector.unprojectVector( mouse2D.clone(), camera );
...