openmesh/src/OpenMesh/Tools/Utils/StripifierT_impl.hh

/* ========================================================================= *
 *                                                                           *
 *                               OpenMesh                                    *
 *           Copyright (c) 2001-2023, RWTH-Aachen University                 *
 *           Department of Computer Graphics and Multimedia                  *
 *                          All rights reserved.                             *
 *                            www.openmesh.org                               *
 *                                                                           *
 *---------------------------------------------------------------------------*
 * This file is part of OpenMesh.                                            *
 *---------------------------------------------------------------------------*
 *                                                                           *
 * Redistribution and use in source and binary forms, with or without        *
 * modification, are permitted provided that the following conditions        *
 * are met:                                                                  *
 *                                                                           *
 * 1. Redistributions of source code must retain the above copyright notice, *
 *    this list of conditions and the following disclaimer.                  *
 *                                                                           *
 * 2. Redistributions in binary form must reproduce the above copyright      *
 *    notice, this list of conditions and the following disclaimer in the    *
 *    documentation and/or other materials provided with the distribution.   *
 *                                                                           *
 * 3. Neither the name of the copyright holder nor the names of its          *
 *    contributors may be used to endorse or promote products derived from   *
 *    this software without specific prior written permission.               *
 *                                                                           *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS       *
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED *
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A           *
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER *
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,  *
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,       *
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR        *
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF    *
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING      *
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS        *
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.              *
 *                                                                           *
 * ========================================================================= */



//=============================================================================
//
//  CLASS StripifierT - IMPLEMENTATION
//
//=============================================================================

#define OPENMESH_STRIPIFIERT_C

//== INCLUDES =================================================================

#include <OpenMesh/Tools/Utils/StripifierT.hh>
#include <list>


//== NAMESPACES ===============================================================

namespace OpenMesh {


  //== IMPLEMENTATION ==========================================================

template <class Mesh>
StripifierT<Mesh>::
StripifierT(Mesh& _mesh) :
    mesh_(_mesh)
{

}

template <class Mesh>
StripifierT<Mesh>::
~StripifierT() {

}

template <class Mesh>
size_t
StripifierT<Mesh>::
stripify()
{
  // preprocess:  add new properties
  mesh_.add_property( processed_ );
  mesh_.add_property( used_ );
  mesh_.request_face_status();

  // build strips
  clear();
  build_strips();

  // postprocess:  remove properties
  mesh_.remove_property(processed_);
  mesh_.remove_property(used_);
  mesh_.release_face_status();

  return n_strips();
}


//-----------------------------------------------------------------------------


template <class Mesh>
void
StripifierT<Mesh>::
build_strips()
{
  Strip                           experiments[3];
  typename Mesh::HalfedgeHandle   h[3];
  FaceHandles                     faces[3];
  typename FaceHandles::iterator  fh_it, fh_end;
  typename Mesh::FaceIter         f_it, f_end=mesh_.faces_end();



  // init faces to be un-processed and un-used
  // deleted or hidden faces are marked processed
  if (mesh_.has_face_status())
  {
    for (f_it=mesh_.faces_begin(); f_it!=f_end; ++f_it)
      if (mesh_.status(*f_it).hidden() || mesh_.status(*f_it).deleted())
        processed(*f_it) = used(*f_it) = true;
      else
        processed(*f_it) = used(*f_it) = false;
  }
  else
  {
    for (f_it=mesh_.faces_begin(); f_it!=f_end; ++f_it)
      processed(*f_it) = used(*f_it) = false;
  }



  for (f_it=mesh_.faces_begin(); true; )
  {
    // find start face
    for (; f_it!=f_end; ++f_it)
      if (!processed(*f_it))
        break;
    if (f_it==f_end) break; // stop if all have been processed


    // collect starting halfedges
    h[0] = mesh_.halfedge_handle(*f_it);
    h[1] = mesh_.next_halfedge_handle(h[0]);
    h[2] = mesh_.next_halfedge_handle(h[1]);


    // build 3 strips, take best one
    size_t best_length = 0;
    size_t best_idx    = 0;

    for (size_t i=0; i<3; ++i)
    {
      build_strip(h[i], experiments[i], faces[i]);

      const size_t length = experiments[i].size();
      if ( length  > best_length)
      {
        best_length = length;
        best_idx    = i;
      }

      for (fh_it=faces[i].begin(), fh_end=faces[i].end();
           fh_it!=fh_end; ++fh_it)
        used(*fh_it) = false;
    }


    // update processed status
    fh_it  = faces[best_idx].begin();
    fh_end = faces[best_idx].end();
    for (; fh_it!=fh_end; ++fh_it)
      processed(*fh_it) = true;



    // add best strip to strip-list
    strips_.push_back(experiments[best_idx]);
  }
}


//-----------------------------------------------------------------------------


template <class Mesh>
void
StripifierT<Mesh>::
build_strip(typename Mesh::HalfedgeHandle _start_hh,
            Strip& _strip,
            FaceHandles& _faces)
{
  std::list<unsigned int>  strip;
  typename Mesh::HalfedgeHandle   hh;
  typename Mesh::FaceHandle       fh;


  // reset face list
  _faces.clear();


  // init strip
  strip.push_back(mesh_.from_vertex_handle(_start_hh).idx());
  strip.push_back(mesh_.to_vertex_handle(_start_hh).idx());


  // walk along the strip: 1st direction
  hh = mesh_.prev_halfedge_handle(mesh_.opposite_halfedge_handle(_start_hh));
  while (1)
  {
    // go right
    hh = mesh_.next_halfedge_handle(hh);
    hh = mesh_.opposite_halfedge_handle(hh);
    hh = mesh_.next_halfedge_handle(hh);
    if (mesh_.is_boundary(hh)) break;
    fh = mesh_.face_handle(hh);
    if (processed(fh) || used(fh)) break;
    _faces.push_back(fh);
    used(fh) = true;
    strip.push_back(mesh_.to_vertex_handle(hh).idx());

    // go left
    hh = mesh_.opposite_halfedge_handle(hh);
    hh = mesh_.next_halfedge_handle(hh);
    if (mesh_.is_boundary(hh)) break;
    fh = mesh_.face_handle(hh);
    if (processed(fh) || used(fh)) break;
    _faces.push_back(fh);
    used(fh) = true;
    strip.push_back(mesh_.to_vertex_handle(hh).idx());
  }


  // walk along the strip: 2nd direction
  bool flip(false);
  hh = mesh_.prev_halfedge_handle(_start_hh);
  while (1)
  {
    // go right
    hh = mesh_.next_halfedge_handle(hh);
    hh = mesh_.opposite_halfedge_handle(hh);
    hh = mesh_.next_halfedge_handle(hh);
    if (mesh_.is_boundary(hh)) break;
    fh = mesh_.face_handle(hh);
    if (processed(fh) || used(fh)) break;
    _faces.push_back(fh);
    used(fh) = true;
    strip.push_front(mesh_.to_vertex_handle(hh).idx());
    flip = true;

    // go left
    hh = mesh_.opposite_halfedge_handle(hh);
    hh = mesh_.next_halfedge_handle(hh);
    if (mesh_.is_boundary(hh)) break;
    fh = mesh_.face_handle(hh);
    if (processed(fh) || used(fh)) break;
    _faces.push_back(fh);
    used(fh) = true;
    strip.push_front(mesh_.to_vertex_handle(hh).idx());
    flip = false;
  }

  if (flip) strip.push_front(strip.front());



  // copy final strip to _strip
  _strip.clear();
  _strip.reserve(strip.size());
  std::copy(strip.begin(), strip.end(), std::back_inserter(_strip));
}


//=============================================================================
} // namespace OpenMesh
  //=============================================================================