/Users/jab/Documents/Teaching/02585/GEL2_and_demos/GEL/src/GLGraphics/SimpleTrackBall.h

#ifndef __GLGRAPHICS_SIMPLETRACKBALL_H__
#define __GLGRAPHICS_SIMPLETRACKBALL_H__

#include "CGLA/CGLA.h"
#include "CGLA/Vec3f.h"


namespace GLGraphics
{

                class SimpleTrackBall
                {
                                CGLA::Vec3f center;
        
                                float r;     // Distance to center (origin)
                                float theta; // Horizontal angle (azimuth)
                                float phi;   // vertical angle (zenith)
        
                                float da;    // angle increment
                                float dr;    // zoom increment

                                bool firsttime;   // used by the roll function
                                float oldx, oldy;

                                int X,Y,Z;

                                void roll_x(float dx);
                                void roll_y(float dy);

                public:

                                SimpleTrackBall(const CGLA::Vec3f& _center, float _r): 
                                                center(_center),
                                                r(_r), theta(static_cast<float>(M_PI_2)), phi(0.0f), 
                                                da(static_cast<float>(M_PI/100.0)), dr(r/100.0f), firsttime(true),
                                                X(0), Y(1), Z(2)
                                                {} 

                                void gl_view() const;

                                void get_view(CGLA::Vec3f& c, CGLA::Vec3f& e, CGLA::Vec3f& u)
                                                {
                                                                const CGLA::Vec3f up(0,1,0);
                                                                float x = r * sin(theta) * cos(phi);
                                                                float y = r * cos(theta);
                                                                float z = r * sin(theta) * sin(phi);
                                                                CGLA::Vec3f dir(x,y,z);
                                                                CGLA::Vec3f eye = center + CGLA::Vec3f(dir[X], dir[Y], dir[Z]);
                                                                c = center;
                                                                e = eye;
                                                                u = CGLA::Vec3f(up[X], up[Y], up[Z]);
                                                }

                                void up_axis(char up);

                                void farther()
                                                {
                                                                r += dr;
                                                }
                
                                void closer()
                                                {
                                                                r = CGLA::s_max(0.0f, r - dr);
                                                }

                                void roll(int x, int y);

                                void set_center(const CGLA::Vec3f& _center)
                                                {
                                                                center = _center;
                                                }
                };

}
#endif