EgtGraphics/SceneBasic.cpp

//----------------------------------------------------------------------------
//  EgalTech 2013-2014
//----------------------------------------------------------------------------
// File : SceneBasic.cpp         Data : 03.02.14           Versione : 1.5b1
// Contenuto : Implementazione della classe gestione scena.
//
//
//
// Modifiche : 29.01.14 DS Creazione modulo.
//
//
//----------------------------------------------------------------------------

//--------------------------- Include ----------------------------------------
#include "stdafx.h"
#include "Scene.h"
#include "GraphObjs.h"
#include "DllMain.h"
#include "/EgtDev/Include/EgtILogger.h"
#include "/EgtDev/Include/EGnStringUtils.h"
#include "/EgtDev/Include/EGkFrame3d.h"
#include "/EgtDev/Include/EGkGdbConst.h"
#include "/EgtDev/Include/EGkGeomDB.h"

using namespace std ;

//--------------------------- Constants --------------------------------------
static const double MIN_EXTENSION = 50 ;
static const double MIN_ZCLIP_EXT = 5000 ;


//----------------------------------------------------------------------------
IEGrScene*
CreateEGrScene( void)
{
   return static_cast<IEGrScene*> ( new(nothrow) Scene) ;
}

//----------------------------------------------------------------------------
Scene::Scene( void)
{
  // Context data
   m_hDC = nullptr ;
   m_hRC = nullptr ;
   memset( &m_wglewc, 0, sizeof( WGLEWContext)) ;
   memset( &m_glewc, 0, sizeof( GLEWContext)) ;
   m_bNewWay = false ;
  // Camera e viewport
   m_ptCenter = ORIG ;
   SetCamera( 0, 0, 0) ;
   m_nViewportW = 0 ;
   m_nViewportH = 0 ;
  // Sfondo
   m_BackTop.Set( 128, 128, 128) ;
   m_BackBottom.Set( 128, 128, 128) ;
  // GeomData
   m_pGeomDB = nullptr ;
   m_colDef.Set( 0, 0, 0) ;
  // Extension
   SetExtension( BBox3d( -MIN_EXTENSION, -MIN_EXTENSION, -MIN_EXTENSION,
                         MIN_EXTENSION, MIN_EXTENSION, MIN_EXTENSION)) ;
  // WinRect
   m_bOutlineWR = true ;
   m_colorWR.Set( 0, 0, 0) ;
   m_bWinRect = false ;
}

//----------------------------------------------------------------------------
Scene::~Scene( void)
{
}

//----------------------------------------------------------------------------
bool
Scene::Init( IGeomDB* pGeomDB)
{
   m_pGeomDB = pGeomDB ;
   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::CreateContext( HDC hDC, int nDriver, bool b2Buff, int nColorBits, int nDepthBits)
{
  // verifico validità Device Context
   if ( hDC == nullptr)
      return false ;
   m_hDC = hDC ;

  // riporto nei limiti il tipo di driver
   if ( nDriver < OD_SOFT)
      nDriver = OD_SOFT ;
   else if ( nDriver > OD_NEW)
      nDriver = OD_NEW ;

  // assegno formato pixel
   PIXELFORMATDESCRIPTOR pfd ;
   memset( &pfd, 0, sizeof(PIXELFORMATDESCRIPTOR)) ;
   pfd.nSize  = sizeof(PIXELFORMATDESCRIPTOR) ;
   pfd.nVersion   = 1 ;
   pfd.dwFlags    = ( b2Buff ? PFD_DOUBLEBUFFER : 0) | PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW ;
   pfd.iPixelType = PFD_TYPE_RGBA ;
   pfd.cColorBits = nColorBits ;
   pfd.cDepthBits = nDepthBits ;
   pfd.iLayerType = PFD_MAIN_PLANE ;

   int nPixelFormat = ChoosePixelFormat( m_hDC, &pfd) ; 
   if ( nPixelFormat == 0)
      return false ;
   if ( nDriver == OD_SOFT) {
      int nPixFormGen = ChooseGenPixelFormat( nPixelFormat, b2Buff, nColorBits, nDepthBits) ;
      if ( nPixFormGen != 0)
         nPixelFormat = nPixFormGen ;
   }
   if ( ! SetPixelFormat( m_hDC, nPixelFormat, &pfd))
      return false ; 

   HGLRC tempContext = wglCreateContext( m_hDC) ;
   wglMakeCurrent( m_hDC, tempContext) ;

   GLenum WglewInitResult ;
   WglewInitResult = wglewInit() ;

   if ( WglewInitResult != GLEW_OK)
      LOG_INFO( GetEGrLogger(), "WGLEW is not initialized !")

   int attribs[10] ;
   if ( nDriver == OD_SOFT) {
      attribs[0] = WGL_CONTEXT_MAJOR_VERSION_ARB ;
      attribs[1] = 1 ;
      attribs[2] = WGL_CONTEXT_MINOR_VERSION_ARB ;
      attribs[3] = 1 ;
      attribs[4] = 0 ;
   }
   else if ( nDriver == OD_OLD) {
      attribs[0] = WGL_CONTEXT_MAJOR_VERSION_ARB ;
      attribs[1] = 2 ;
      attribs[2] = WGL_CONTEXT_MINOR_VERSION_ARB ;
      attribs[3] = 0 ;
      attribs[4] = 0 ;
   }
   else {
      attribs[0] = WGL_CONTEXT_MAJOR_VERSION_ARB ;
      attribs[1] = 3 ;
      attribs[2] = WGL_CONTEXT_MINOR_VERSION_ARB ;
      attribs[3] = 0 ;
      attribs[4] = 0 ;
   }

   if ( wglewIsSupported( "WGL_ARB_create_context") == 1) {
      m_hRC = wglCreateContextAttribsARB( m_hDC, 0, attribs) ;
      wglMakeCurrent( m_hDC, NULL) ;
      wglDeleteContext( tempContext) ;
      wglMakeCurrent( m_hDC, m_hRC) ;
   }
   else {
     //It's not possible to make a GL 3.x context. Use the old style context (GL 2.1 and before)
      m_hRC = tempContext ;
      LOG_INFO( GetEGrLogger(), "WGL_ARB_create_context missing !")
   }

  // verifico validità Rendering Context
   if ( m_hRC == nullptr)
      return false ;

   GLenum GlewInitResult ;
   glewExperimental = GL_TRUE ;
   GlewInitResult = glewInit() ;

   if ( GlewInitResult != GLEW_OK)
      LOG_INFO( GetEGrLogger(), "GLEW is not initialized !")

  // verifico se posso lavorare in modalità nuova
   m_bNewWay = ( nDriver == OD_NEW  &&  glewIsSupported( "GL_VERSION_3_0") == 1) ;
   if ( ! m_bNewWay)
      LOG_INFO( GetEGrLogger(), "OpenGL old way rendering !")

  // reset stato di errore di OpenGL
   glGetError() ;

   return true ;
}

//----------------------------------------------------------------------------
int
Scene::ChooseGenPixelFormat( int nPfd, bool b2Buff, int nColorBits, int nDepthBits)
{
   PIXELFORMATDESCRIPTOR pfdR ;


  // verifica del pixel format proposto
   int nTotPfd = DescribePixelFormat( m_hDC, nPfd, sizeof(PIXELFORMATDESCRIPTOR), &pfdR) ;
   if ( pfdR.dwFlags & PFD_GENERIC_FORMAT  &&  
        ! ( pfdR.dwFlags & PFD_GENERIC_ACCELERATED))
      return nPfd ;

  // eventuale ricerca di un pixel format soddisfacente 
   int nIOpt = 0 ;
   int nErrOpt = 1000 ;
   for ( int nI = 1 ; nI <= nTotPfd ; nI ++) {
      DescribePixelFormat( m_hDC, nI, sizeof(PIXELFORMATDESCRIPTOR), &pfdR) ;
      if ( pfdR.dwFlags & PFD_GENERIC_FORMAT  &&  
           ! (pfdR.dwFlags & PFD_GENERIC_ACCELERATED)  &&
           ( ! b2Buff  ||  pfdR.dwFlags & PFD_DOUBLEBUFFER)) {
         int nErr = abs( nColorBits - pfdR.cColorBits) + 
                    abs( nDepthBits - pfdR.cDepthBits) ;
         if ( nErr < nErrOpt) {
            nErrOpt = nErr ;
            nIOpt = nI ;
         }
      }
   }

   return nIOpt ;
}

//----------------------------------------------------------------------------
bool
Scene::MakeCurrent( void)
{
  // se RC della scena non è definito, errore
   if ( m_hRC == nullptr)
      return false ;

  // se RC della scena non è quello corrente, lo imposto
   HGLRC hRC = wglGetCurrentContext() ;
   if ( m_hRC != hRC)
      return ( wglMakeCurrent( m_hDC, m_hRC) != 0) ;

   return true ;
}

//----------------------------------------------------------------------------
string
Scene::GetOpenGLInfo( void)
{
   string sInfo = "OpenGL " ;

   if ( MakeCurrent()) {
      const char* p ;
      if ( ( p = reinterpret_cast<const char*> ( glGetString( GL_VERSION))) != nullptr)
         sInfo += p ;
      sInfo += " " ;
      if ( ( p = reinterpret_cast<const char*> ( glGetString( GL_VENDOR))) != nullptr)
         sInfo += p ;
      sInfo += " " ;
      if ( ( p = reinterpret_cast<const char*> ( glGetString( GL_RENDERER))) != nullptr)
         sInfo += p ;
   }
   else
      sInfo += "ERROR" ;

  // reset stato di errore di OpenGL
   glGetError() ;

   return sInfo ;
}

//----------------------------------------------------------------------------
string
Scene::GetGLSLInfo( void)
{
   string sInfo = "GLSL " ;

   if ( MakeCurrent()) {
      const char* p ;
      if ( ( p = reinterpret_cast<const char*> ( glGetString( GL_SHADING_LANGUAGE_VERSION))) != nullptr)
         sInfo += p ;
      else
         sInfo += "NONE" ;
   }
   else
      sInfo += "ERROR" ;

  // reset stato di errore di OpenGL
   glGetError() ;

   return sInfo ;
}

//----------------------------------------------------------------------------
string
Scene::GetPixelFormatInfo( void)
{
   string sInfo = "PixFmt " ;

   if ( MakeCurrent()) {
      int nPixFmt ;
      PIXELFORMATDESCRIPTOR Pfd ;
      if ( ( nPixFmt = GetPixelFormat( m_hDC)) > 0  &&
           DescribePixelFormat( m_hDC, nPixFmt, sizeof(PIXELFORMATDESCRIPTOR), &Pfd) > 0) {
        // indice
         sInfo += ToString( nPixFmt) ;
        // tipo di driver
         if ( ! ( Pfd.dwFlags & PFD_GENERIC_FORMAT))
            sInfo += " ICD" ;
         else if ( Pfd.dwFlags & PFD_GENERIC_ACCELERATED)
            sInfo += " MCD" ;
         else
            sInfo += " GEN" ;
        // singolo o doppio buffer
         sInfo += ( ( Pfd.dwFlags & PFD_DOUBLEBUFFER) ? " BUFF2" : " BUFF1") ;
        // RGBA o COLORINDEX
         sInfo += ( ( Pfd.iPixelType == PFD_TYPE_RGBA) ? " RGBA" : " CI") ;
        // color bits
         sInfo += ToString( Pfd.cColorBits) ;
        // depth bits
         sInfo += " Z" + ToString( Pfd.cDepthBits) ;
      }
      else
         sInfo = "NO DESCRIBE" ;
   }
   else
      sInfo += "ERROR" ;

  // reset stato di errore di OpenGL
   glGetError() ;

   return sInfo ;
}

//----------------------------------------------------------------------------
bool
Scene::RedrawWindow( void)
{
   HWND hWnd = ::WindowFromDC( m_hDC) ;
   if ( hWnd == nullptr)
      return false ;

   return ( ::RedrawWindow( hWnd, nullptr, nullptr, RDW_INVALIDATE | RDW_UPDATENOW) != 0) ;
}

//----------------------------------------------------------------------------
bool
Scene::SetExtension( const BBox3d& b3Ext)
{
   if ( b3Ext.IsEmpty())
      m_b3ExtWorld.Set( -MIN_EXTENSION, -MIN_EXTENSION, -MIN_EXTENSION,
                         MIN_EXTENSION, MIN_EXTENSION, MIN_EXTENSION) ;
   else
      m_b3ExtWorld = b3Ext ;
   m_bExtViewOk = false ;
   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::CalcExtView( void)
{
  // verifico se il calcolo è necessario
   if ( m_bExtViewOk  &&  m_bUpOk)
      return true ;
  // calcolo direzione camera Up
   if ( ! CalcDirUp())
      return false ;
  // calcolo il riferimento di vista
   Frame3d frView ;
   if ( ! CalcCameraFrame( frView))
      return false ;
  // calcolo l'estensione nel riferimento di vista
   m_b3ExtView = m_b3ExtWorld ;
   m_b3ExtView.ToLoc( frView) ;
   m_bExtViewOk = true ;
   return m_bExtViewOk ;
}

//----------------------------------------------------------------------------
bool
Scene::CalcDimViewFromExtView( void)
{
  // calcolo estensione nel riferimento di vista
   if ( ! CalcExtView())
      return false ;

  // recupero gli ingombri
   Point3d ptMin ;
   Point3d ptMax ;
   if ( ! m_b3ExtView.GetMinMax( ptMin, ptMax))
      return false ;

  // ricavo le dimensioni
   const double COEFF = 1.05 ;
   double dHalfWidth = COEFF * max( fabs( ptMin.x), fabs( ptMax.x)) ;
   double dHalfHeight = COEFF * max( fabs( ptMin.y), fabs( ptMax.y)) ;

  // adatto le dimensioni a quelle della vista
   return AdjustDimView( dHalfWidth, dHalfHeight) ;
}

//----------------------------------------------------------------------------
bool
Scene::AdjustDimView( double dHalfWidth, double dHalfHeight)
{
  // se non assegnate, recupero dimensioni vista
   if ( m_nViewportW == 0) {
      HWND hWnd = ::WindowFromDC( m_hDC) ;
      RECT rect ;
      if ( ! ::GetClientRect( hWnd, &rect))
         return false ;
      m_nViewportW = rect.right ;
      m_nViewportH = rect.bottom ;
     // aggiorno la vista
      glViewport( 0, 0, m_nViewportW, m_nViewportH) ; 
     // verifico presenza errori
      GLenum nErr = glGetError() ;
      if ( nErr != GL_NO_ERROR) {
         string sOut = "First glViewport OpenGL error " + ToString( (int)nErr) ;
         LOG_INFO( GetEGrLogger(), sOut.c_str())
      }
   }

  // adatto il rapporto tra le dimensioni calcolate a quello delle dimensioni della vista
   double dAspect = m_nViewportH / ( double) m_nViewportW ;
   if ( dAspect * dHalfWidth > dHalfHeight) {
      m_dHalfWidth = dHalfWidth ;
      m_dHalfHeight = dAspect * dHalfWidth ;
   }                                        
   else {
      m_dHalfWidth = dHalfHeight / dAspect ;
      m_dHalfHeight = dHalfHeight ;
   }

   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::CalcClippingPlanesFromExtView( void)
{
  // calcolo estensione nel riferimento di vista
   if ( ! CalcExtView())
      return false ;

  // recupero gli ingombri
   Point3d ptCenter ;
   Vector3d vtExtent ;
   if ( ! m_b3ExtView.GetCenterExtent( ptCenter, vtExtent))
      return false ;
  // ricavo la posizione dei piani di clipping sull'asse Z di vista
   const double EXP_COEFF = 1.1 ;
   double dExtent = __max( ( EXP_COEFF * vtExtent.z), MIN_ZCLIP_EXT) ;
   m_dZNear = - ( ptCenter.z + dExtent) ;
   m_dZFar = - ( ptCenter.z - dExtent) ;
   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::Reshape( int nW, int nH)
{
   if ( ! MakeCurrent())
      return false ;

  // assegno le dimensioni della vista
   m_nViewportW = nW ;
   m_nViewportH = nH ;

  // aggiorno la vista
   glViewport( 0, 0, m_nViewportW, m_nViewportH) ; 

  // verifico presenza errori
   GLenum nErr = glGetError() ;
   if ( nErr != GL_NO_ERROR) {
      string sOut = "Reshape OpenGL error " + ToString( (int)nErr) ;
      LOG_INFO( GetEGrLogger(), sOut.c_str())
   }

  // aggiorno
   AdjustDimView( m_dHalfWidth, m_dHalfHeight) ;

  // ridisegno
   return Draw() ;
}

//----------------------------------------------------------------------------
bool
Scene::SetBackground( Color BackTop, Color BackBottom)
{
   m_BackTop = BackTop ;
   m_BackBottom = BackBottom ;

   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::Background( void)
{
  // imposto il rendering corrente
   if ( ! MakeCurrent())
      return false ;

  // cancello lo Zbuffer
   glClearDepth( 1) ;
   glClear( GL_DEPTH_BUFFER_BIT) ;

  // se lo sfondo ha un colore uniforme
   if ( m_BackTop == m_BackBottom) {
     // imposto il colore dello sfondo e lo cancello
      glClearColor( m_BackTop.GetRed(), m_BackTop.GetGreen(), m_BackTop.GetBlue(), m_BackTop.GetAlpha()) ;
      glClear( GL_COLOR_BUFFER_BIT) ;
      return true ;
   }

  // rendo neutre matrici di proiezione e di modello/vista
   glMatrixMode( GL_PROJECTION) ;
   glLoadIdentity() ;
   glMatrixMode( GL_MODELVIEW) ;
   glLoadIdentity() ;

  // disabilito lo Zdepth
   glDisable( GL_DEPTH_TEST) ;

  // disegno lo sfondo con due colori
   if ( ! m_bNewWay) {
      glBegin( GL_TRIANGLE_STRIP) ;
      glColor3f( m_BackBottom.GetRed(), m_BackBottom.GetGreen(), m_BackBottom.GetBlue()) ;
      glVertex3f( -1, -1, 0.5) ;
      glVertex3f( 1, -1, 0.5) ;
      glColor3f( m_BackTop.GetRed(), m_BackTop.GetGreen(), m_BackTop.GetBlue()) ;
      glVertex3f( -1, 1, 0.5) ;
      glVertex3f( 1, 1, 0.5) ;
      glEnd() ;
   }
   else {
      unsigned int nVaoId ;
      unsigned int nVboId ;
     // definizione
      glGenVertexArrays( 1, &nVaoId) ;
      if ( nVaoId == 0)
         return false ;
      glBindVertexArray( nVaoId) ;
      glGenBuffers( 1, &nVboId) ;
      glBindBuffer( GL_ARRAY_BUFFER, nVboId) ;
      glBufferData( GL_ARRAY_BUFFER, 8 * SIZEV3F, NULL, GL_STATIC_DRAW) ;
      glVertexPointer( 3, GL_FLOAT, 2 * SIZEV3F, ((void*)(0))) ;
      glEnableClientState( GL_VERTEX_ARRAY) ;
      glColorPointer( 3, GL_FLOAT, 2 * SIZEV3F, ((void*)(1 * SIZEV3F))) ;
      glEnableClientState( GL_COLOR_ARRAY) ;
      Vert3f v3V ;
      Vert3f v3C ;
     // bottom left
      v3V.Set( -1, -1, 0.5) ;
      glBufferSubData( GL_ARRAY_BUFFER, 0 * SIZEV3F, SIZEV3F, &v3V) ;
      v3C.Set( m_BackBottom.GetRed(), m_BackBottom.GetGreen(), m_BackBottom.GetBlue()) ;
      glBufferSubData( GL_ARRAY_BUFFER, 1 * SIZEV3F, SIZEV3F, &v3C) ;
     // bottom right
      v3V.Set( 1, -1, 0.5) ;
      glBufferSubData( GL_ARRAY_BUFFER, 2 * SIZEV3F, SIZEV3F, &v3V) ;
      // v3C constant
      glBufferSubData( GL_ARRAY_BUFFER, 3 * SIZEV3F, SIZEV3F, &v3C) ;
     // top left
      v3V.Set( -1, 1, 0.5) ;
      glBufferSubData( GL_ARRAY_BUFFER, 4 * SIZEV3F, SIZEV3F, &v3V) ;
      v3C.Set( m_BackTop.GetRed(), m_BackTop.GetGreen(), m_BackTop.GetBlue()) ;
      glBufferSubData( GL_ARRAY_BUFFER, 5 * SIZEV3F, SIZEV3F, &v3C) ;
     // top right
      v3V.Set( 1, 1, 0.5) ;
      glBufferSubData( GL_ARRAY_BUFFER, 6 * SIZEV3F, SIZEV3F, &v3V) ;
      // v3C constant
      glBufferSubData( GL_ARRAY_BUFFER, 7 * SIZEV3F, SIZEV3F, &v3C) ;
     // disegno
      glDrawArrays( GL_TRIANGLE_STRIP, 0, 4) ;
     // cancellazione
      glBindBuffer( GL_ARRAY_BUFFER, 0) ;
      glDeleteBuffers( 1, &nVboId) ;
      glBindVertexArray( 0) ;
      glDeleteVertexArrays( 1, &nVaoId) ;
   }

   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::Prepare( void)
{
  // imposto il rendering corrente
   if ( ! MakeCurrent())
      return false ;

  // eventuale ricalcolo parametri di vista
   CalcDirUp() ;

  // imposto matrice di proiezione
   glMatrixMode( GL_PROJECTION) ;
   glLoadIdentity() ;
   glOrtho( - m_dHalfWidth, m_dHalfWidth, - m_dHalfHeight, m_dHalfHeight, m_dZNear, m_dZFar) ;

  // imposto matrice modello/vista
   glMatrixMode( GL_MODELVIEW) ;
   glLoadIdentity() ;
   Point3d ptCamera = m_ptCenter + m_dDistCamera * m_vtDirCamera ;
   gluLookAt( ptCamera.x, ptCamera.y, ptCamera.z,
              m_ptCenter.x, m_ptCenter.y, m_ptCenter.z,
              m_vtUp.x, m_vtUp.y, m_vtUp.z) ;

  // verifico presenza errori
   GLenum nErr = glGetError() ;
   if ( nErr != GL_NO_ERROR) {
      string sOut = "Prepare OpenGL error " + ToString( (int)nErr) ;
      LOG_INFO( GetEGrLogger(), sOut.c_str())
   }

   return true ;
}

//----------------------------------------------------------------------------
bool
Scene::Draw( void)
{
  // sistemo lo sfondo e lo Zbuffer
   if ( ! Background())
      return false ;

  // imposto la camera
   if ( ! Prepare())
      return false ;

  // imposto l'utilizzo dello Zbuffer
   glDepthFunc( GL_LESS) ;
   glEnable( GL_DEPTH_TEST) ;

  // aggiorno il colore di default
   if ( m_pGeomDB != nullptr)
      m_pGeomDB->GetDefaultColor( m_colDef) ;

  // imposto la dimensione standard dei punti
   glPointSize( 3) ;

  // disegno le geometrie del DB
   DrawGroup( GDB_ID_ROOT, GDB_MD_STD, GDB_ST_ON) ;

  // aggiungo disegni diretti (senza test Zbuffer)
   glDisable( GL_DEPTH_TEST) ;
   DrawWinRect() ;

  // aggiorno
   glFlush() ;

  // verifico presenza errori
   GLenum nErr = glGetError() ;
   if ( nErr != GL_NO_ERROR) {
      string sOut = "Draw OpenGL error " + ToString( (int)nErr) ;
      LOG_INFO( GetEGrLogger(), sOut.c_str())
   }

  // scambio i buffer back e front ( eseguita solo se previsti)
   if ( ! SwapBuffers( m_hDC))
      LOG_INFO( GetEGrLogger(), "Draw SwapBuffers error")

   return true ;
}

/*------------------------------------------------------------------------------------------*/
bool
Scene::Project( const Point3d& ptWorld, Point3d& ptView)
{
   if ( ! MakeCurrent())
      return false ;

  // recupero le matrici
   GLdouble ModelView[ 16] ;
   glGetDoublev( GL_MODELVIEW_MATRIX, ModelView) ;
   GLdouble Projection[ 16] ;
   glGetDoublev( GL_PROJECTION_MATRIX, Projection) ;
   GLint Viewport[ 4] ;
   glGetIntegerv( GL_VIEWPORT, Viewport) ;

  // eseguo la proiezione
   // l'asse y della vista OpenGL va in alto con l'origine in basso,
   // quello di Windows va in basso con l'origine in alto 
   int nRes =gluProject( ptWorld.x, ptWorld.y, ptWorld.z,
                         ModelView, Projection, Viewport,
                         &ptView.x, &ptView.y, &ptView.z) ;
   ptView.y = (double) Viewport[3] - ptView.y ;

   return ( nRes == GL_TRUE) ;
}

/*------------------------------------------------------------------------------------------*/
bool
Scene::UnProject( const Point3d& ptView, Point3d& ptWorld)
{
   if ( ! MakeCurrent())
      return false ;

  // recupero le matrici
   GLdouble ModelView[ 16] ;
   glGetDoublev( GL_MODELVIEW_MATRIX, ModelView) ;
   GLdouble Projection[ 16] ;
   glGetDoublev( GL_PROJECTION_MATRIX, Projection) ;
   GLint Viewport[ 4] ;
   glGetIntegerv( GL_VIEWPORT, Viewport) ;

  // eseguo la contro proiezione
   // l'asse y della vista OpenGL va in alto con l'origine in basso,
   // quello di Windows va in basso con l'origine in alto 
   int nRes = gluUnProject( ptView.x, ((double) Viewport[3] - ptView.y), ptView.z,
                            ModelView, Projection, Viewport,
                            &ptWorld.x, &ptWorld.y, &ptWorld.z) ;

   return ( nRes == GL_TRUE) ;
}

//----------------------------------------------------------------------------
void
Scene::Destroy( void)
{
  // cancellazione eventuali ObjEgrGraphics attaccati a oggetti geometrici
   DeleteObjGraphicsGroup( GDB_ID_ROOT) ;

  // cancellazione rendering context
   wglMakeCurrent( nullptr, nullptr) ;
   if ( m_hRC != nullptr) {
      wglDeleteContext( m_hRC) ;
      m_hRC = nullptr ;
   }
}