(a) III: Bad assignment (costly)
(b) IV: Good assignment (no costs)
Figure 4: (a) (Case III) a pair of nodes and becomes neighbours and after the assignment. This undesired assignment adds 1 to the costs. (b) (Case IV) nodes and which are not adjacent in the object graph are assigned to nodes which are also not adjacent in the scene graph . This assignment is associated with no additional cost in (5.6).