public int getChildIndex(Spatial sp) {
        return children.indexOf(sp);
    }
<code>getChildIndex</code> returns the index of the given spatial
in this node's list of children.
@param sp
         The spatial to look up
@return  The index of the spatial in the node's children, or -1
         if the spatial is not attached to this node
jme3-core/src/main/java/com/jme3/scene/Node.java