/// update of the rotation matrix 'mat_cur', using the position
/// of the beginning of the dragging and the current position.
/// both coordinates mapped to the surface of the virtual trackball.
inline void update(void)
{
math::vec3 v_from = map_sphere(v_down, center, radius);
math::vec3 v_to = map_sphere(v_cur, center, radius);
if (drag) q_cur = from_ball_points(v_from, v_to) * q_end;
to_matrix(mat_cur, q_cur);
}
/// indicates the beginning of the dragging.
void ArcBall::click( int x, int y )
{
m_lastRot = m_currentRot;
v_mouse_down.setX( x );
v_mouse_down.setY( y );
v_mouse_down.setZ( 0.0 );
v_from = map_sphere( x, y );
}
/// sets the current position and calculates the current
/// rotation matrix.
void ArcBall::drag( int x, int y )
{
QVector3D v_to = map_sphere( x, y );
QVector3D perp = QVector3D::crossProduct( v_from, v_to);
if ( perp.length() > Epsilon )
{
q_current_rotation.setX( perp.x() );
q_current_rotation.setY( perp.y() );
q_current_rotation.setZ( perp.z() );;
q_current_rotation.setScalar( ( v_from.x() * v_to.x() ) + ( v_from.y() * v_to.y() ) + ( v_from.z() * v_to.z() ) );
}
else
{
q_current_rotation.setX( 0.0 );
q_current_rotation.setY( 0.0 );
q_current_rotation.setZ( 0.0 );
q_current_rotation.setScalar( 0.0 );
}
m_currentRot.setToIdentity();
m_currentRot.rotate( q_current_rotation );
m_currentRot = m_currentRot * m_lastRot ;
}
