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http://www.gamedev.net/reference/programming/features/quatcam/page3.asp

A Simple Quaternion-based Camera

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Last year may go down in history as The Year of the Hardware Acceleration. Much of the work rasterizing and texture-mapping polygons was off-loaded to dedicated hardware.

Features - Rotating Objects Using Quaternions

http://www.gamasutra.com/view/feature/3278/rotating_objects_using_quaternions.php