PluginFunctions.cc

/*===========================================================================*\
*                                                                            *
*                              OpenFlipper                                   *
*      Copyright (C) 2001-2011 by Computer Graphics Group, RWTH Aachen       *
*                           www.openflipper.org                              *
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*  This file is part of OpenFlipper.                                         *
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/*===========================================================================*\
*                                                                            *
*   $Revision$                                                       *
*   $LastChangedBy$                                                *
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\*===========================================================================*/




//=============================================================================
//
//  Plugin Functions
//
//=============================================================================

#include <OpenFlipper/common/Types.hh>
#include <QGLWidget>

#include "PluginFunctions.hh"
#include "PluginFunctionsCore.hh"

namespace PluginFunctions {

 /** \brief DONT USE DIRECTLY!!
  *
  * This Pointer will be used to access the data trees root in the plugin. Never use it directly as
 *  the internal Structure will change. Use the Access functions instead */
static BaseObject* objectRoot_ = 0;

/** \brief DONT USE DIRECTLY!!
 *
 * This pointer is internally used to acces the examiner widget in the main apllication
 */
static std::vector< glViewer* > examiner_widgets_;

/** \brief DONT USE DIRECTLY!!
 *
 * This vector is used internally to access properties of all viewers
 */
static std::vector< Viewer::ViewerProperties* > viewerProperties_;

/// TODO : Remove this variable and implement multiView correctly here
static glViewer*  examiner_widget_;

/// Contains the currently active examiner
static unsigned int activeExaminer_ = 0;

static bool internalLightHandling_ = true;

/** \brief DONT USE DIRECTLY!!
 *
 * The pointer to the beginning of the scenegraph nodes ( only the nodes belonging to objects )
 * Between the actual root node ( sceneGraphRootNode_ ) and this node global nodes could be added
 * This pointer is internally used to access the scenegraphs root node
 */
static SeparatorNode* dataRootNode_ = 0;

/** This node is used to add nodes between the root node of the scenegraph and the objects separator node.
* It is directly below the sceneGraphRootNode_
*/
static SeparatorNode* dataSeparatorNode_ = 0;

/** \brief Scenegraph global nodes root
 */
static SeparatorNode* sceneGraphRootNodeGlobal_ = 0;

/** \brief Scenegraph root node
 */
static SeparatorNode* sceneGraphRootNode_ = 0;

/** \brief a dummy properties object returned as a reference if the real object does not exist
 *
 */
static Viewer::ViewerProperties dummyProperties;


/** \brief DONT USE DIRECTLY!!
 *
 * This pointer is used internally
 */
static ViewObjectMarker* defaultMarker_ = 0;

/** \brief DONT USE DIRECTLY!!
 *
 * This pointer is used internally
 */
static QGLWidget* shareGLWidget_ = 0;

/** This is a unique id for the running OpenFlipper instance. Use it to identify yourself on the network
*/
static int viewerId_ = 0;

/// Number of currently open objects
static int objectCounter_ = 0;

/// Number of current target objects
static int targetCounter_ = 0;

/// Map that holds the object handles
static std::map<int, BaseObject*> objectMap_;

/// Map of scenegraph widget generators
QMap< std::string ,ACG::QtWidgets::SceneGraphWidgetGenerator* > sceneGraphGenerators_;

void setDataRoot( BaseObject* _root ) {
   objectRoot_ = _root;
}

int viewers( ) {
  return examiner_widgets_.size();
}

void disableExaminerLightHandling() {
  internalLightHandling_ = false;  
}

bool examinerLightHandling() {
  return internalLightHandling_;  
}

int viewerId() {
  return viewerId_;
}

void setViewers( std::vector< glViewer* > _viewerWidgets ) {
   PluginFunctions::examiner_widgets_ = _viewerWidgets;
   PluginFunctions::examiner_widget_ =  examiner_widgets_[0];

   // Generate a (hopefully) unique viewer id
   QTime time = QTime::currentTime();
   qsrand( time.hour() * 10 + time.minute() * 100 + time.second() * 1000 + time.msec() * 10000  );
   viewerId_ = qrand();
}

void setViewerProperties( std::vector< Viewer::ViewerProperties* > _viewerProperties ) {
   PluginFunctions::viewerProperties_ = _viewerProperties;
}

void setActiveExaminer( const unsigned int _id ) {
  activeExaminer_ = _id;
}

glViewer* viewer(int  _viewerId ) {
   if ( _viewerId < 0 || _viewerId >= (int)examiner_widgets_.size() ) {
     std::cerr << "Requested unknown viewer with id : " << _viewerId << std::endl;
     return examiner_widgets_[activeExaminer()];
   }

   return( examiner_widgets_[_viewerId] );
}

unsigned int activeExaminer( ) {
  return activeExaminer_;
}

QString getEncodedExaminerView() {
  return getEncodedExaminerView(activeExaminer());
}

/// Get the encoded view for the given
QString getEncodedExaminerView(int _viewerId) {

  QString view;

  if ( _viewerId < 0 || _viewerId >= (int)examiner_widgets_.size() ) {
     std::cerr << "Requested unknown viewer with id : " << _viewerId << std::endl;
     examiner_widgets_[activeExaminer()]->encodeView ( view );
     return view;
  }

  examiner_widgets_[_viewerId]->encodeView ( view );
  return view;

}

void setEncodedExaminerView( QString _view ) {
  setEncodedExaminerView( activeExaminer() , _view );
}

void setEncodedExaminerView(int _viewerId , QString _view ) {

  if ( _viewerId < 0 || _viewerId >= (int)examiner_widgets_.size() ) {
     std::cerr << "Requested unknown viewer with id : " << _viewerId << std::endl;
     examiner_widgets_[activeExaminer()]->decodeView ( _view );
  }

  examiner_widgets_[_viewerId]->decodeView ( _view );
}

void setDataSeparatorNodes( SeparatorNode* _dataSeparatorNode ) {
  
  // The function should only be called once by the core. 

  // Set the separatorNode
  PluginFunctions::dataSeparatorNode_ = _dataSeparatorNode;

  
  if ( PluginFunctions::dataSeparatorNode_->nChildren() != 1 ){
    std::cerr << "Only one child allowed for dataSeparatorNode on initialization!" << std::endl;
    std::cerr << "The Core has initialized the scenegraph in a strange way!" << std::endl;
  }
  
  // Set the root node for the data objects
  // which has to be a child of the dataSeparatorNode_
  PluginFunctions::dataRootNode_ = dynamic_cast<ACG::SceneGraph::SeparatorNode*> (*(PluginFunctions::dataSeparatorNode_->childrenBegin()) );
  
}

void setSceneGraphRootNode( SeparatorNode* _root_node ) {
   PluginFunctions::sceneGraphRootNode_ = _root_node;
}

void setSceneGraphRootNodeGlobal( SeparatorNode* _root_node ) {
   PluginFunctions::sceneGraphRootNodeGlobal_ = _root_node;
}

bool getPickedObject(const unsigned int _node_idx , BaseObjectData*& _object) {
  for ( ObjectIterator o_it(PluginFunctions::ALL_OBJECTS) ; o_it != PluginFunctions::objectsEnd(); ++o_it) {
    if ( o_it->picked( _node_idx ) ) {
      _object = *o_it;
      return true;
    }
  }
  return false;
}


bool getSourceIdentifiers( std::vector<int>& _identifiers  ) {
  _identifiers.clear();

  for ( ObjectIterator o_it(PluginFunctions::ALL_OBJECTS) ; o_it != PluginFunctions::objectsEnd(); ++o_it) {
    if ( o_it->source() )
      _identifiers.push_back ( o_it->id() );
  }
  return (_identifiers.size() >0 );
}

bool getTargetIdentifiers( std::vector<int>& _identifiers  ) {
  _identifiers.clear();

  for ( ObjectIterator o_it(PluginFunctions::ALL_OBJECTS) ; o_it != PluginFunctions::objectsEnd(); ++o_it) {
    if ( o_it->target() )
      _identifiers.push_back ( o_it->id() );
  }
  return (_identifiers.size() >0 );
}

// ===============================================================================
// Get objects
// ===============================================================================

bool getObject(  const int _identifier , BaseObject*& _object ) {

  if ( _identifier == -1 )
    return false;

  // Obsolete:
  //_object = objectRoot_->childExists( _identifier );
  
  // Search for specified object in object map:
  std::map<int, BaseObject*>::iterator it;
  it = objectMap_.find(_identifier);
  // Get object
  _object = (it != objectMap_.end() ? it->second : 0);
  
  return ( _object != 0 );
}

bool getObject(  const int _identifier , BaseObjectData*& _object ) {

  if ( _identifier == -1 )
    return false;

  // Obsolete: BaseObject* object = objectRoot_->childExists( _identifier );
  
  // Search for specified object in object map:
  std::map<int, BaseObject*>::iterator it;
  it = objectMap_.find(_identifier);
  // Get object
  BaseObject* object = (it != objectMap_.end() ? it->second : 0);
  
  _object = dynamic_cast< BaseObjectData* >(object);
  return ( _object != 0 );
}

int getObjectId( const QString _name ) {
  if(_name.isEmpty()) return -1;

  BaseObject* object = objectRoot_->childExists( _name );
  return object ? object->id() : -1;
}

// ===============================================================================
// ===============================================================================

bool object_exists(  const int _identifier ) {

  if ( _identifier == -1 )
    return false;

  BaseObject* object = objectRoot_->childExists( _identifier );
  return ( object != 0 );
}

//===============================================================================

bool getAllMeshes( std::vector<int>& _identifiers  ) {

  _identifiers.clear();

  // find changed manipulator
  for ( PluginFunctions::ObjectIterator o_it(PluginFunctions::ALL_OBJECTS,typeId("TriangleMesh")) ;
                                        o_it != PluginFunctions::objectsEnd(); ++o_it)  {
    _identifiers.push_back( o_it->id() );
  }

  return (_identifiers.size() > 0);
}

bool get_all_object_identifiers( std::vector<int>& _identifiers  ) {

  _identifiers.clear();

  // find changed manipulator
  for ( PluginFunctions::ObjectIterator o_it(PluginFunctions::ALL_OBJECTS) ;
                                        o_it != PluginFunctions::objectsEnd(); ++o_it)  {
    _identifiers.push_back( o_it->id() );
  }

  return (_identifiers.size() > 0);
}

void setBackColor( OpenMesh::Vec4f _color) {
  for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
    PluginFunctions::viewerProperties(i).backgroundColor(_color);
}

void setFixedView(int _mode, int _viewer ) {

  if ( (_viewer != ACTIVE_VIEWER ) && ( ( _viewer < 0 ) || _viewer >= (int)examiner_widgets_.size()) ){
    std::cerr << "Unable to set fixed view. Wrong viewer id (" << _viewer << ")" << std::endl;
    return;
  }

  switch ( _mode ){
    case VIEW_TOP : //TOP
      PluginFunctions::viewingDirection( ACG::Vec3d(0.0, -1.0, 0.0), ACG::Vec3d(0.0, 0.0, -1.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    case VIEW_BOTTOM : //BOTTOM
      PluginFunctions::viewingDirection( ACG::Vec3d(0.0, 1.0, 0.0), ACG::Vec3d(0.0, 0.0, -1.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    case VIEW_LEFT : //LEFT
      PluginFunctions::viewingDirection( ACG::Vec3d(1.0, 0.0, 0.0), ACG::Vec3d(0.0, 1.0, 0.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    case VIEW_RIGHT : //RIGHT
      PluginFunctions::viewingDirection( ACG::Vec3d(-1.0, 0.0, 0.0), ACG::Vec3d(0.0, 1.0, 0.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    case VIEW_FRONT : //FRONT
      PluginFunctions::viewingDirection( ACG::Vec3d(0.0, 0.0, -1.0), ACG::Vec3d(0.0, 1.0, 0.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    case VIEW_BACK : //BACK
      PluginFunctions::viewingDirection( ACG::Vec3d(0.0, 0.0, 1.0), ACG::Vec3d(0.0, 1.0, 0.0), _viewer );
      PluginFunctions::allowRotation(!PluginFunctions::viewerProperties().rotationLocked(), _viewer);
      break;
    default : //Free View
      PluginFunctions::allowRotation(true, _viewer);
      break;
  }

  if ( _viewer == ACTIVE_VIEWER )
    viewerProperties(activeExaminer()).currentViewingDirection( _mode );
  else
    viewerProperties( _viewer ).currentViewingDirection( _mode );
}

QPoint mapToGlobal(const QPoint _point ) {
  return examiner_widgets_[activeExaminer_]->glMapToGlobal(_point);
}

QPoint mapToLocal( const QPoint _point ) {
  return examiner_widgets_[activeExaminer_]->glMapFromGlobal(_point);
}

void setDrawMode( const ACG::SceneGraph::DrawModes::DrawMode _mode , int _viewer) {

  if ( _viewer == ACTIVE_VIEWER )
    viewerProperties(activeExaminer()).drawMode(_mode);
  else if ( _viewer == ALL_VIEWERS )
    for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
      viewerProperties(i).drawMode(_mode);
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    viewerProperties(_viewer).drawMode(_mode);
  else
    std::cerr << "Requested illegal viewer for setting DrawMode!!" << std::endl;

}

/** Get the current draw Mode of the examiner widget.\n
 *
 * The DrawModes are defined at ACG/Scenegraph/DrawModes.hh \n
 * They can be combined.
 */
ACG::SceneGraph::DrawModes::DrawMode drawMode( int _viewer ) {
  if ( _viewer == ACTIVE_VIEWER ) {
    return viewerProperties(activeExaminer()).drawMode();
  } else if ( _viewer == ALL_VIEWERS )
    std::cerr << "Please select viewer to get viewing direction!" << std::endl;
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    return viewerProperties(_viewer).drawMode();
  else
    std::cerr << "Requested illegal viewer for viewingDirection!!" << std::endl;

  return viewerProperties(activeExaminer()).drawMode();
}

bool scenegraphPick( ACG::SceneGraph::PickTarget _pickTarget, const QPoint &_mousePos, unsigned int &_nodeIdx, unsigned int &_targetIdx, ACG::Vec3d *_hitPointPtr=0 ) {

   return examiner_widgets_[activeExaminer_]->pick( _pickTarget,_mousePos,_nodeIdx,_targetIdx,_hitPointPtr );
}

bool scenegraphPick( const unsigned int _examiner, ACG::SceneGraph::PickTarget _pickTarget, const QPoint &_mousePos, unsigned int &_nodeIdx, unsigned int &_targetIdx, ACG::Vec3d *_hitPointPtr=0 ) {

  if ( _examiner >= examiner_widgets_.size() ) {
    std::cerr << "Wrong examiner id" << std::endl;
    return false;
  }
  return examiner_widgets_[_examiner]->pick( _pickTarget,_mousePos,_nodeIdx,_targetIdx,_hitPointPtr );
}

bool scenegraphRegionPick( ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list)
{
  return examiner_widgets_[activeExaminer_]->pick_region( _pickTarget, _region, _list);
}

bool scenegraphRegionPick( const unsigned int                         _examiner,
                           ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list)
{
  if ( _examiner >= examiner_widgets_.size() ) {
    std::cerr << "Wrong examiner id" << std::endl;
    return false;
  }
  return examiner_widgets_[_examiner]->pick_region( _pickTarget, _region, _list);
}

bool scenegraphRegionPick( ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<ACG::Vec3d>&                       _points)
{
  return examiner_widgets_[activeExaminer_]->pick_region( _pickTarget, _region, _list, _points);
}

bool scenegraphRegionPick( const unsigned int                         _examiner,
                           ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<ACG::Vec3d>&                       _points)
{
  if ( _examiner >= examiner_widgets_.size() ) {
    std::cerr << "Wrong examiner id" << std::endl;
    return false;
  }
  return examiner_widgets_[_examiner]->pick_region( _pickTarget, _region, _list, _points);
}

bool scenegraphRegionPick( ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<float>&                            _depths)
{
  return examiner_widgets_[activeExaminer_]->pick_region( _pickTarget, _region, _list, _depths);
}

bool scenegraphRegionPick( const unsigned int                         _examiner,
                           ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<float>&                            _depths)
{
  if ( _examiner >= examiner_widgets_.size() ) {
    std::cerr << "Wrong examiner id" << std::endl;
    return false;
  }
  return examiner_widgets_[_examiner]->pick_region( _pickTarget, _region, _list, _depths);
}

bool scenegraphRegionPick( ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<float>&                            _depths,
                           QVector<ACG::Vec3d>&                       _points)
{
  return examiner_widgets_[activeExaminer_]->pick_region( _pickTarget, _region, _list, _depths, _points);
}

bool scenegraphRegionPick( const unsigned int                         _examiner,
                           ACG::SceneGraph::PickTarget                _pickTarget,
                           const QRegion&                             _region,
                           QList<QPair<unsigned int, unsigned int> >& _list,
                           QVector<float>&                            _depths,
                           QVector<ACG::Vec3d>&                       _points)
{
  if ( _examiner >= examiner_widgets_.size() ) {
    std::cerr << "Wrong examiner id" << std::endl;
    return false;
  }
  return examiner_widgets_[_examiner]->pick_region( _pickTarget, _region, _list, _depths, _points);
}

//Warning : Dont use template function as external static pointer for examiner widget is not resolved correctly!!
void traverse( ACG::SceneGraph::MouseEventAction  &_action ) {
  // Single pass action, as the mouse action will only update the graph.
  // If its changed, it will be set to dirty and an automatic redraw is triggered.
  ACG::SceneGraph::traverse(sceneGraphRootNode_, _action );
}

const std::string pickMode () {
  // No seperate draw modes available all should have the same so take first
  return viewerProperties().pickMode();
}

void pickMode ( std::string _mode) {
  // switch to default marker
  setViewObjectMarker (defaultViewObjectMarker ());
  viewerProperties().pickMode(_mode);
}

Viewer::ActionMode actionMode() {
   return viewerProperties().actionMode();
}

void actionMode ( Viewer::ActionMode _mode) {

  viewerProperties().actionMode(_mode);
}

void shareGLWidget (QGLWidget *_widget)
{
  shareGLWidget_ = _widget;
}

QGLWidget *shareGLWidget ()
{
  return shareGLWidget_;
}

void getCurrentViewImage(QImage& _image) {
  viewer( activeExaminer() )->snapshot( _image );
}

Viewer::ViewerProperties& viewerProperties(int _id) {
  if ( _id >= (int)viewerProperties_.size() ) {
    std::cerr << " Error, requested properties for non-existing Viewer!" << std::endl;
    return dummyProperties;
  }

  if ( _id == -1 )
    _id = activeExaminer_;

  return ( *viewerProperties_[_id] );

}

void perspectiveProjection( int _viewer ) {
  if ( _viewer == ACTIVE_VIEWER ) {
    examiner_widgets_[activeExaminer_]->perspectiveProjection();
  } else if ( _viewer == ALL_VIEWERS )
    for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
      examiner_widgets_[i]->perspectiveProjection();
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    examiner_widgets_[_viewer]->perspectiveProjection();
  else
    std::cerr << "Requested illegal viewer for perspectiveProjection()!!" << std::endl;
}

void orthographicProjection( int _viewer ) {
  if ( _viewer == ACTIVE_VIEWER ) {
    examiner_widgets_[activeExaminer_]->orthographicProjection();
  } else if ( _viewer == ALL_VIEWERS )
    for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
      examiner_widgets_[i]->orthographicProjection();
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    examiner_widgets_[_viewer]->orthographicProjection();
  else
    std::cerr << "Requested illegal viewer for orthographicProjection()!!" << std::endl;
}

void setFOVY( double _fovy) {
  
  // Set FOVY for all viewers
  for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
    examiner_widgets_[i]->setFOVY(_fovy);
}

void allowRotation(bool _mode, int _viewer ) {
  if ( _viewer == ACTIVE_VIEWER ) {
    examiner_widgets_[activeExaminer_]->allowRotation(_mode);
  } else if ( _viewer == ALL_VIEWERS )
    for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
      examiner_widgets_[i]->allowRotation(_mode);
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    examiner_widgets_[_viewer]->allowRotation(_mode);
  else {
    std::cerr << "Requested illegal viewer for allowRotation!!" << std::endl;
    return;
  }
  
  if ( _viewer == ACTIVE_VIEWER )
    viewerProperties(activeExaminer()).rotationLocked( !_mode );
  else
    viewerProperties( _viewer ).rotationLocked( !_mode );
}

bool allowRotation( int _viewer ) {

  if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    return examiner_widgets_[_viewer]->allowRotation();
  else {

    std::cerr << "Requested illegal viewer for isRotationAllowed!!" << std::endl;
    return false;
  }
}

void setMainGLContext() {
  examiner_widget_->makeCurrent();
}

void viewingDirection(const ACG::Vec3d &_dir, const ACG::Vec3d &_up , int _viewer ) {
  if ( _viewer == ACTIVE_VIEWER ) {
    examiner_widgets_[activeExaminer_]->viewingDirection(_dir,_up);
  } else if ( _viewer == ALL_VIEWERS )
    for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
      examiner_widgets_[i]->viewingDirection(_dir,_up);
  else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
    examiner_widgets_[_viewer]->viewingDirection(_dir,_up);
  else
    std::cerr << "Requested illegal viewer for viewingDirection!!" << std::endl;
}

void lookAt(const ACG::Vec3d& _eye, const ACG::Vec3d& _center, const ACG::Vec3d& _up, int _viewer) {
    
    if ( _viewer == ACTIVE_VIEWER ) {
        examiner_widgets_[activeExaminer_]->lookAt(_eye,_center, _up);
    } else if ( _viewer == ALL_VIEWERS )
        for ( uint i = 0 ; i < examiner_widgets_.size(); ++i )
            examiner_widgets_[i]->lookAt(_eye,_center, _up);
        else if ( ( _viewer >= 0 ) && _viewer < (int)examiner_widgets_.size() )
            examiner_widgets_[_viewer]->lookAt(_eye,_center, _up);
        else
            std::cerr << "Requested illegal viewer for viewingDirection!!" << std::endl;
}

const ACG::Vec3d trackBallCenter( int _viewer ) {