jme3 BoundingVolume.merge


when I try to merge 2 BoundingVolume I always get "java.lang.NullPointerException" error

what could the problem be ?

BoundingVolume border=Spatial1.getWorldBound();
BoundingVolume border2=Spatial2.getWorldBound();

without row 3. and 4. I dont get any error, but when I add 3. or 4. row then I will get the error.
also I am curious about the result of merged volume (if successful)
Let Spatial1 and 2 are 2 long boxes with grad 90, then after merging I will get a huge box, or a L like shape?
+ are there anyway to see the BoundingVolume in jme3? (may be BoundingDebugger?)

You can't access the world bound of a spatial unless it is properly updated. Make sure to call rootNode.updateGeometricState() before accessing the world bounds.