function onDocumentMouseDown( event ) {
  event.preventDefault();
  
  mouse.x = ( event.clientX / window.innerWidth ) * 2 - 1;
  mouse.y = - ( event.clientY / window.innerHeight ) * 2 + 1;



  // find intersections
  raycaster.setFromCamera( mouse, camera );
  var intersects = raycaster.intersectObjects( scene.children );
  var vector = new THREE.Vector3().copy( intersects[ 0 ].point );

  intersects[ 0 ].object.worldToLocal( vector );
  mat.uniforms.mouse.value.x = vector.x;
  mat.uniforms.mouse.value.y = vector.y;

}

document.addEventListener( 'mousemove', onDocumentMouseDown, false );