arcball.cpp

/**********************************************************************

  arcball.cpp


          --------------------------------------------------

  GLUI User Interface Toolkit
  Copyright (c) 1998 Paul Rademacher
     Feb 1998, Paul Rademacher (rademach@cs.unc.edu)
     Oct 2003, Nigel Stewart - GLUI Code Cleaning

  WWW:    http://sourceforge.net/projects/glui/
  Forums: http://sourceforge.net/forum/?group_id=92496

  This software is provided 'as-is', without any express or implied
  warranty. In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
  claim that you wrote the original software. If you use this software
  in a product, an acknowledgment in the product documentation would be
  appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
  misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

**********************************************************************/

#include "arcball.h"

#include <cstdio>


/**************************************** Arcball::Arcball() ****/
/* Default (void) constructor for Arcball                         */

Arcball::Arcball()
{
    rot_ptr = &rot;
    init();
}

/**************************************** Arcball::Arcball() ****/
/* Takes as argument a mat4 to use instead of the internal rot  */

Arcball::Arcball(mat4 *mtx)
{
    rot_ptr = mtx;
}


/**************************************** Arcball::Arcball() ****/
/* A constructor that accepts the screen center and arcball radius*/

Arcball::Arcball(const vec2 &_center, float _radius)
{
    rot_ptr = &rot;
    init();
    set_params(_center, _radius);
}


/************************************** Arcball::set_params() ****/

void Arcball::set_params(const vec2 &_center, float _radius)
{
    center      = _center;
    radius      = _radius;
}

/*************************************** Arcball::init() **********/

void Arcball::init()
{
    center.set( 0.0, 0.0 );
    radius         = 1.0;
    q_now          = quat_identity();
    *rot_ptr       = identity3D();
    q_increment    = quat_identity();
    rot_increment  = identity3D();
    is_mouse_down  = false;
    is_spinning    = false;
    damp_factor    = 0.0;
    zero_increment = true;
}

/*********************************** Arcball::mouse_to_sphere() ****/

vec3 Arcball::mouse_to_sphere(const vec2 &p)
{
    float mag;
    vec2  v2 = (p - center) / radius;
    vec3  v3( v2[0], v2[1], 0.0 );

    mag = v2*v2;

    if ( mag > 1.0 )
        v3.normalize();
    else
        v3[VZ] = (float) sqrt( 1.0 - mag );

    /* Now we add constraints - X takes precedence over Y */
    if ( constraint_x )
    {
        v3 = constrain_vector( v3, vec3( 1.0, 0.0, 0.0 ));
    }
    else if ( constraint_y )
        {
            v3 = constrain_vector( v3, vec3( 0.0, 1.0, 0.0 ));
        }

    return v3;
}


/************************************ Arcball::constrain_vector() ****/

vec3 Arcball::constrain_vector(const vec3 &vector, const vec3 &axis)
{
    return (vector-(vector*axis)*axis).normalize();
}

/************************************ Arcball::mouse_down() **********/

void Arcball::mouse_down(int x, int y)
{
    down_pt.set( (float)x, (float) y );
    is_mouse_down = true;

    q_increment   = quat_identity();
    rot_increment = identity3D();
    zero_increment = true;
}


/************************************ Arcball::mouse_up() **********/

void Arcball::mouse_up()
{
    q_now = q_drag * q_now;
    is_mouse_down = false;
}


/********************************** Arcball::mouse_motion() **********/

void Arcball::mouse_motion(int x, int y, int shift, int ctrl, int alt)
{
    /* Set the X constraint if CONTROL key is pressed, Y if ALT key */
    set_constraints( ctrl != 0, alt != 0 );

    vec2 new_pt( (float)x, (float) y );
    vec3 v0 = mouse_to_sphere( down_pt );
    vec3 v1 = mouse_to_sphere( new_pt );

    vec3 cross = v0^v1;

    q_drag.set( cross, v0 * v1 );

    //    *rot_ptr = (q_drag * q_now).to_mat4();
    mat4 temp = q_drag.to_mat4();
    *rot_ptr = *rot_ptr * temp;

    down_pt = new_pt;

    /* We keep a copy of the current incremental rotation (= q_drag) */
    q_increment   = q_drag;
    rot_increment = q_increment.to_mat4();

    set_constraints(false, false);

    if ( q_increment.s < .999999 )
    {
        is_spinning = true;
        zero_increment = false;
    }
    else
    {
        is_spinning = false;
        zero_increment = true;
    }
}


/********************************** Arcball::mouse_motion() **********/

void Arcball::mouse_motion(int x, int y)
{
    mouse_motion(x, y, 0, 0, 0);
}


/***************************** Arcball::set_constraints() **********/

void Arcball::set_constraints(bool _constraint_x, bool _constraint_y)
{
    constraint_x = _constraint_x;
    constraint_y = _constraint_y;
}

/***************************** Arcball::idle() *********************/

void Arcball::idle()
{
    if (is_mouse_down)
    {
        is_spinning = false;
        zero_increment = true;
    }

    if (damp_factor < 1.0f)
        q_increment.scale_angle(1.0f - damp_factor);

    rot_increment = q_increment.to_mat4();

    if (q_increment.s >= .999999f)
    {
        is_spinning = false;
        zero_increment = true;
    }
}


/************************ Arcball::set_damping() *********************/

void Arcball::set_damping(float d)
{
    damp_factor = d;
}