text: #ifndef AC_GEPONSRF_H
  #define AC_GEPONSRF_H
  //
  // (C) Copyright 1993-1999 by Autodesk, Inc.
  //
  // Permission to use, copy, modify, and distribute this software in
  // object code form for any purpose and without fee is hereby granted, 
  // provided that the above copyright notice appears in all copies and 
  // that both that copyright notice and the limited warranty and
  // restricted rights notice below appear in all supporting 
  // documentation.
  //
  // AUTODESK PROVIDES THIS PROGRAM "AS IS" AND WITH ALL FAULTS. 
  // AUTODESK SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTY OF
  // MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE.  AUTODESK, INC. 
  // DOES NOT WARRANT THAT THE OPERATION OF THE PROGRAM WILL BE
  // UNINTERRUPTED OR ERROR FREE.
  //
  // Use, duplication, or disclosure by the U.S. Government is subject to 
  // restrictions set forth in FAR 52.227-19 (Commercial Computer
  // Software - Restricted Rights) and DFAR 252.227-7013(c)(1)(ii)
  // (Rights in Technical Data and Computer Software), as applicable.
  //
  // DESCRIPTION:
  // class AcGePointOnSurface to keep information of a point belonging
  // to a surface.
  
  #include "gepent3d.h"
  #pragma pack (push, 8)
  
  class AcGeSurface;
  
  class
  #ifdef AC_GEPONSRF_CPP
  GE_DLLEXPORT
  #else
  GE_DLLIMPORT
  #endif
  AcGePointOnSurface : public AcGePointEnt3d
  {
  public:
      AcGePointOnSurface();
      AcGePointOnSurface(const AcGeSurface& surf);
      AcGePointOnSurface(const AcGeSurface& surf, const AcGePoint2d& param);
      AcGePointOnSurface(const AcGePointOnSurface& src);
  
      // Assignment operator.
      //
      AcGePointOnSurface& operator =     (const AcGePointOnSurface& src);
  
      // Query functions.
      //
      const AcGeSurface*  surface        () const;
      AcGePoint2d         parameter      () const;
  
      // Functions to evaluate a point.
      //
      AcGePoint3d         point          () const;
      AcGePoint3d         point          (const AcGePoint2d& param );
      AcGePoint3d         point          (const AcGeSurface& surf,
                                          const AcGePoint2d& param);
  
      // Functions to evaluate surface normal.
      //
      AcGeVector3d        normal         () const;
      AcGeVector3d        normal         (const AcGePoint2d& param );
      AcGeVector3d        normal         (const AcGeSurface& surf,
                                          const AcGePoint2d& param);
      // Functions to evaluate derivatives.
      //
      AcGeVector3d        uDeriv         (int order) const;
      AcGeVector3d        uDeriv         (int order, const AcGePoint2d& param);
      AcGeVector3d        uDeriv         (int order, const AcGeSurface& surf,
                                          const AcGePoint2d& param);
  
      AcGeVector3d        vDeriv         (int order) const;
      AcGeVector3d        vDeriv         (int order, const AcGePoint2d& param);
      AcGeVector3d        vDeriv         (int order, const AcGeSurface& surf,
                                          const AcGePoint2d& param);
  
      // Functions to evaluate the mixed partial.
      //
      AcGeVector3d        mixedPartial   () const;
      AcGeVector3d        mixedPartial   (const AcGePoint2d& param);
      AcGeVector3d        mixedPartial   (const AcGeSurface& surf,
                                          const AcGePoint2d& param);
  
      // Functions to compute the tangent vector in a given direction.
      //
      AcGeVector3d        tangentVector  (const AcGeVector2d& vec) const;
      AcGeVector3d        tangentVector  (const AcGeVector2d& vec,
                                          const AcGePoint2d& param);
      AcGeVector3d        tangentVector  (const AcGeVector2d& vec,
                                          const AcGeSurface& vecSurf,
                                          const AcGePoint2d& param);
  
      // Functions to invert a tangent vector to parameter space.
      //
      AcGeVector2d        inverseTangentVector  (const AcGeVector3d& vec) const;
      AcGeVector2d        inverseTangentVector  (const AcGeVector3d& vec,
                                                 const AcGePoint2d& param);
      AcGeVector2d        inverseTangentVector  (const AcGeVector3d& vec,
                                                 const AcGeSurface& surf,
                                                 const AcGePoint2d& param);
      // Set functions.
      //
      AcGePointOnSurface& setSurface     (const AcGeSurface& surf);
      AcGePointOnSurface& setParameter   (const AcGePoint2d& param);
  };
  
  #pragma pack (pop)
  #endif
  
  