Box always in front of the camera

Hi guys,
I am working on a small tower defends game. I need to let player can select where they want to build the tower. Here is the code I create calculate the cursor position and attach the tower at it:

        Vector3f origin = cam.getWorldCoordinates(inputManager.getCursorPosition(),0.0f);
        Vector3f direction = cam.getWorldCoordinates(inputManager.getCursorPosition(),0.3f);
        Ray ray = new Ray(origin,direction);
        CollisionResults results = new CollisionResults();
        rootNode.collideWith(ray, results);
        if(results.size() > 0) {
            CollisionResult closest = results.getClosestCollision();
            Quaternion q = new Quaternion();
            q.lookAt(closest.getContactNormal(), Vector3f.UNIT_Z);

Here is the code that attach tower to the cursor position when player click mouse:

    public void onAnalog(String name, float value,float tpf) {
        if(name.equals("build")) {
            float x = mark.getLocalTranslation().x;
            float y = mark.getLocalTranslation().y;
            float z = mark.getLocalTranslation().z;
            geomTow.setLocalTranslation(x, y, z);
            System.out.println("x: "+x+"\ny: "+y+"\nz: "+z);

But the results show the cube(tower) always move in front of the camera:

I also use the System.out.println(); method to print out the cursor location, here is the results:

x: 0.66858315
y: 0.0
z: 8.816481

x: 0.7650244
y: 0.69080544
z: 7.8164825

And I realized that the cursor position always change when attach the cube to the cursor and don’t change when I disable this:


So the question is:
Does anything wrong there ? How to fix that ?