TAPsOpenGLTrackball.hpp

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/******************************************************************************
TAPsOpenGLTrackball.hpp

An object using OpenGL for Trackball Rotation.

SUKITTI PUNAK   (10/06/2004)
UPDATE          (08/10/2010)
--------------------------------------------------------------------------------
Example of Usage:
-----------------
For providing a trackball rotation on OpenGL
    First create a trackball
        OpenGLTrackball *world_trackball_ptr = new OpenGLTrackball();

    Put this in a mouse function for starting of motion
        world_trackball_ptr->StartMotion(x, y, w_pix, h_pix);
    And put this in a mouse motion function for moving object by 
    calculating m in trackball
        world_trackball_ptr->MoveObject(x, y, w_pix, h_pix);

    Have it multiply in a display function for rotation
        glMultMatrixd(world_trackball_ptr->m);
    and make sure that it will be updated somewhere by
        glutPostRedisplay();

    Reset the trackball rotation with
        world_trackball_ptr->Reset();

    Where w_pix and h_pix should be integer global variables 
    for width and height sizes in pixel units respectively.
******************************************************************************/
#include <iostream>
#include <cmath>
#include "../Core/TAPsLib.hpp"

#ifndef TAPs_OPENGL_TRACKBALL_HPP
#define TAPs_OPENGL_TRACKBALL_HPP

BEGIN_NAMESPACE_TAPs
//=============================================================================
class OpenGLTrackball {
public:
    OpenGLTrackball();
    ~OpenGLTrackball();

    // The mouse position is x and y.
    // The size of viewport is w_pix (width) and h_pix (height).
    void MoveObject(int x, int y, int w_pix, int h_pix);
    void StartMotion(int x, int y, int w_pix, int h_pix);
    // purpose: reset the trackball back to the original position.
    // (by set the trackball matrix to an identity matrix.)
    void Reset();
    // These should be in private section, but it is easier to keep them here.
    double Om[16];      // old rotation matrix
    double m[16];       // new rotation matrix
    const double * const RetRotationMatrixDouble4by4 ()
        { return m; }
    //---------------------------------------------------------------
private:
    double M[16];       // temp matrix
    int curx, cury;         // current position (x and y)
    int startX, startY;     // start position (x and y)
    double lastPos[3];      // last position
    double rotationAxis[3]; // axis
    double rotationAngle;   // rotation angle

    // HELPER FUNCTION
    // The mouse position is x and y.
    // The size of viewport is w_pix (width) and h_pix (height).
    // v[3] is a position.
    void Trackball_ptov(int x, int y, int width, int height, double v[3]);
};
//=============================================================================
END_NAMESPACE_TAPs
//-----------------------------------------------------------------------------
// Include definition if TAPs_USE_EXPORT is not defined
#if !defined( TAPs_USE_EXPORT )
    #include "TAPsOpenGLTrackball.cpp"
#endif
//-----------------------------------------------------------------------------
#endif
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