var projector = new THREE.Projector();

var world_vector = new THREE.Vector3(0,0,1);

var vector = projector.projectVector(world_vector, camera);

var halfWidth = window.innerWidth / 2;
var halfHeight = window.innerHeight / 2;

var result = {

	x: Math.round(vector.x * halfWidth + halfWidth),
	y: Math.round(-vector.y * halfHeight + halfHeight)

};

?