Submitted on: 18 October 2002.
Revised on: 16 November 2002.
Accepted on: 03 December 2002.
___________________IEEE COMPUTER GRAPHICS AND APPLICATIONS
Submitted on: 12 March 2007.
Revised on: 30 June 2007.
Accepted on: 15 July 2007.
___________________IEEE COMPUTER GRAPHICS AND APPLICATIONS
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