viewgraphs.fm—8 
Nevatia - 14 
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Example of curved objects 
• Modelled by classes of generalized cylinders 
• Symmetry properties between the contours 
• Allowed junctions between the contours 
Handling Complexity 
• Combinatorial Search can be expensive 
• Parallelogram search can be O (n 4 ) 
• Solution: 
• Limit search space 
• only constant number in a fixed search space 
• Group Hierarchically 
• parallels, L-junctions 
• U- contours 
• parallelograms 
• combining parallelograms 
• adding walls 
viewgraphs.fm—7 
8/4/95