public Vector3f getScreenCoordinates(Vector3f worldPos) {
        return getScreenCoordinates(worldPos, null);
    }
Converts the given position from world space to screen space.

@param worldPos a location in world coordinates (not null, unaffected)
@return a new (3-D) location vector (in screen coordinates)
@see Camera#getScreenCoordinates
jme3-core/src/main/java/com/jme3/renderer/Camera.java