OCCT

// Created on: 1993-01-21
// Created by: Peter KURNEV
// Copyright (c) 1993-1999 Matra Datavision
// Copyright (c) 1999-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#include <BRepClass3d.hxx>

#include <BRep_Builder.hxx>
#include <BRepClass3d_SolidClassifier.hxx>
#include <TopAbs_Orientation.hxx>
#include <TopAbs_State.hxx>
#include <TopoDS_Iterator.hxx>
#include <TopoDS_Shell.hxx>
#include <TopoDS_Solid.hxx>

static bool IsInternal(const TopoDS_Shell& aSx);

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

TopoDS_Shell BRepClass3d::OuterShell(const TopoDS_Solid& aSolid)
{
  bool                        bFound;
  double                      aTol;
  TopoDS_Solid                aSDx;
  TopoDS_Shell                aShell, aDummy;
  TopoDS_Iterator             aIt;
  BRep_Builder                aBB;
  BRepClass3d_SolidClassifier aSC;
  //
  if (aSolid.IsNull())
  {
    return aDummy;
  }
  //
  aTol   = 1.e-7;
  bFound = false;
  //
  // if solid has one shell, it will return, without checking orientation
  int aShellCounter = 0;
  for (aIt.Initialize(aSolid); aIt.More(); aIt.Next())
  {
    const TopoDS_Shape& aSx = aIt.Value();
    if (aSx.ShapeType() == TopAbs_SHELL)
    {
      aShell = *((TopoDS_Shell*)&aSx);
      aShellCounter++;
      if (aShellCounter >= 2)
      {
        break;
      }
    }
  }
  if (aShellCounter == 0)
  {
    return aDummy;
  }
  else if (aShellCounter == 1)
  {
    return aShell;
  }
  //
  for (aIt.Initialize(aSolid); aIt.More(); aIt.Next())
  {
    const TopoDS_Shape& aSx = aIt.Value();
    if (aSx.ShapeType() == TopAbs_SHELL)
    {
      aShell = *((TopoDS_Shell*)&aSx);
      if (!IsInternal(aShell))
      {
        aSDx = aSolid;
        aSDx.EmptyCopy();
        aBB.Add(aSDx, aShell);
        //
        aSC.Load(aSDx);
        aSC.PerformInfinitePoint(aTol);
        if (aSC.State() == TopAbs_OUT)
        {
          bFound = true;
          break;
        }
      }
    }
  }
  //
  if (!bFound)
  {
    return aDummy;
  }
  //
  return aShell;
}

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

bool IsInternal(const TopoDS_Shell& aSx)
{
  bool               bInternal;
  TopAbs_Orientation aOr;
  TopoDS_Iterator    aIt;
  //
  bInternal = false;
  //
  aIt.Initialize(aSx);
  if (aIt.More())
  {
    const TopoDS_Shape& aSy = aIt.Value();
    aOr                     = aSy.Orientation();
    bInternal               = (aOr == TopAbs_INTERNAL);
  }
  //
  return bInternal;
}