arcball.h

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/*
    Sheep - A Rigid Body Dynamics Engine
    Copyright (C) 2001-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of Sheep.

    Sheep is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    Sheep is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Sheep; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#ifndef SHEEP_FRAMEWORK_ARCBALL_H
#define SHEEP_FRAMEWORK_ARCBALL_H

#include "common/math/quaternion.h"
#include "common/math/vector2.h"
#include "common/math/vector3.h"

#include <cassert>

namespace sheep {

    // This code implements the Arcball device as described in
    // the article "Arcball Rotation Control" by Ken Shoemake
    // (shoemake@graphics.cis.upenn.edu) in "Graphics Gems IV",
    // Academic Press, 1994.

    class Arcball {
    public:
        Arcball();

        void BeginDrag(const Vector2 &p);
        void UpdateDrag(const Vector2 &p);
        void EndDrag();
        void CancelDrag();

        bool IsDragging() const;

        void SetOrientation(const Quaternion &q);
        const Quaternion &GetOrientation() const;

    private:
        Quaternion m_q, m_start_q;
        Vector3 m_from;
        bool m_is_dragging;

        Vector3 point_on_sphere(const Vector2 &p) const;
    };

#include "arcball.inl"

}

#endif  // !SHEEP_FRAMEWORK_ARCBALL_H

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