#include <arcball.h>

Collaboration diagram for MeshLib::CArcball:

Public Member Functions
	CArcball ()
	CArcball (int width, int height, int ox, int oy)
CQrot	update (int nx, int ny)
Private Member Functions
void	_plane2sphere (const CPoint2 &v, CPoint &r)
Private Attributes
CPoint	m_position
double	m_radius
CPoint2	m_center

Detailed Description

CArcball Interface.

Arcball interface is widely used for user interaction, because it is intuitive and efficient. Imagine there is a glass ball centered at the screen user can hold one point on the ball, and drag the ball to rotate it. Everything inisde the ball with be roated accordingly.

Definition at line 28 of file arcball.h.

Constructor & Destructor Documentation

MeshLib::CArcball::CArcball ( ) [inline]

CArcball default constructor

Definition at line 34 of file arcball.h.

{};

CArcball::CArcball	(	int	width,
		int	height,
		int	ox,
		int	oy
	)

CArcball constructor

Parameters:

	width	width of the window
	height	height of the window
	ox	original x position
	oy	original y position

Definition at line 16 of file arcball.cpp.

{
        m_radius = (win_width < win_height )? win_width/2: win_height/2;

  m_center = CPoint2( win_width/2, win_height/2 );

  CPoint2 p(ox,oy);

  _plane2sphere( p, m_position );
}

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Member Function Documentation

void CArcball::_plane2sphere	(	const CPoint2 &	v,
		CPoint &	r
	)			`[private]`

mapping a planar point v to the unit sphere point r

Parameters:

	v	input planar point
	r	output point on the unit sphere

Definition at line 29 of file arcball.cpp.

{

  CPoint2 f = p;
  f /= m_radius;

  double l = sqrt( f*f );

  if( l > 1.0 ){
      q=CPoint( f[0]/l, f[1]/l,0);
      return;
  }

  double fz = sqrt( 1 - l * l );

  q = CPoint( f[0],f[1],fz );
}

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CQrot CArcball::update	(	int	nx,
		int	ny
	)

Update the arcball

Parameters:

	nx	current x-position of mouse
	ny	current y-position of mouse

Returns:: quoternion of the roation from the old position to the new position

Definition at line 49 of file arcball.cpp.

{
    CPoint position;
    _plane2sphere( CPoint2(nx,ny), position );
    CPoint cp = m_position^position;
    CQrot r(m_position * position, cp[0],cp[1],cp[2]);
    m_position = position;

    return r;
}

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