sceneorbiter.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_SCENEORBITER_H
#define SHEEP_FRAMEWORK_SCENEORBITER_H

#include "common/math/point3.h"
#include "common/math/real.h"
#include "common/math/vector2.h"

#include <cassert>
#include <cmath>

//#define REVERSE_AZIMUTH

namespace sheep {

    class SceneOrbiter {
    public:
        enum Movement {
            TUMBLE, TRACK, DOLLY
        };

        // Assuming we have a right-hand coordinate system,
        // azimuth zero is on positive part of the x axis
        // and is increasing in the direction of the positive
        // part of the z axis.

        // Elevation is measured from the x-z plan and is
        // increasing in the direction of the positive part
        // of the y axis.

        SceneOrbiter(
            const Point3 &center = 0,
            Real azimuth = PI / 4.0,
            Real elevation = PI / 4.0,
            Real distance = 1.0
        );

        void Configure(
            const Point3 &center,
            Real azimuth,
            Real elevation,
            Real distance
        );

        // (x, y) is a point on the screen. By convention, it is
        // assumed that the point (-1, -1) is at the lower left
        // corner of the screen whereas the point (1, 1) is at the
        // upper right corner.

        // By convention, azimuth and elevation increase or decrease
        // by PI / 2 for a one unit (mouse) drag, that is, we have:
        // d(azimuth) = PI / 2 * d(x) and d(elevation) = PI / 2 * d(y).

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

        bool IsTumbling() const;
        bool IsTracking() const;
        bool IsDollying() const;
        bool IsDragging() const;

        void SetCenter(const Point3 &center);
        const Point3 &GetCenter() const;

        Point3 GetEyePosition() const;

        Real GetAzimuth() const;
        Real GetElevation() const;
        Real GetDistance() const;

    private:
        Point3 m_center, m_old_center;
        Real m_azimuth, m_old_azimuth;
        Real m_elevation, m_old_elevation;
        Real m_distance, m_old_distance;

        Movement m_movement;
        Vector2 m_old_point;

        bool m_is_dragging;

#ifdef REVERSE_AZIMUTH
        bool m_reverse_azimuth;
#endif  // REVERSE_AZIMUTH

        void tumble(const Vector2 &delta);
        void track(const Vector2 &delta);
        void dolly(const Vector2 &delta);
    };

#include "sceneorbiter.inl"

}

#endif  // !SHEEP_FRAMEWORK_SCENEORBITER_H

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