private void rotateScreenAligned(Camera camera) {
        // co-opt diff for our in direction:
        look.set(camera.getDirection()).negateLocal();
        // co-opt loc for our left direction:
        left.set(camera.getLeft()).negateLocal();
        orient.fromAxes(left, camera.getUp(), look);
        Node parent = spatial.getParent();
        Quaternion rot = new Quaternion().fromRotationMatrix(orient);
        if (parent != null) {
            rot =  parent.getWorldRotation().inverse().multLocal(rot);
            rot.normalizeLocal();
        }
        spatial.setLocalRotation(rot);
        fixRefreshFlags();
    }
Rotates the billboard so it points directly opposite the direction the
camera is facing.

@param camera
           Camera
jme3-core/src/main/java/com/jme3/scene/control/BillboardControl.java