Trackball.H

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// TrackBall.H
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using amrex::Real;

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// Pass the x and y coordinates of the last and current positions of
// the mouse, scaled so they are from (-1.0 ... 1.0).
//
// The resulting rotation is returned as a quaternion rotation 
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extern AmrQuaternion trackball( Real p1x, Real p1y, Real p2x, Real p2y);

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