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panda/src/egg/eggUtilities.I

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// Filename: eggUtilities.I
// Created by:  drose (10Feb99)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://www.panda3d.org/license.txt .
//
// To contact the maintainers of this program write to
// panda3d@yahoogroups.com .
//
////////////////////////////////////////////////////////////////////

#include "eggGroup.h"
#include "eggPrimitive.h"

#include <algorithm>

////////////////////////////////////////////////////////////////////
//     Function: split_vertex
//  Description: Splits a vertex into two or more vertices, each an
//               exact copy of the original and in the same vertex
//               pool.
//
//               The splitting is based on some arbitrary property of
//               the primitives that own the vertex.  In the extreme,
//               each primitive may get a different copy of the
//               vertex, although it is also possible for some
//               primitives to still share vertices.
//
//               This decision is made based on the function object
//               'sequence'.  This object must define the following
//               function:
//
//               int operator () (const EggPrimitive *prim) const;
//
//               This function returns a sequence number, which
//               determines which primitives will share which
//               vertices.  The sequence number 0 refers to the
//               original vertex pointer; other sequence numbers
//               indicate new vertices.  Other than that, the sequence
//               number is totally arbitrary.  Primitives for which
//               the sequence number is the same will end up sharing
//               the same copy of the vertex.
////////////////////////////////////////////////////////////////////
template<class FunctionObject>
void
split_vertex(EggVertex *vert, const FunctionObject &sequence) {
  // Did we start in a happy world?
  vert->test_pref_integrity();
  vert->test_gref_integrity();

  EggVertexPool *pool = vert->get_pool();

  // Define a map of ints to vert pointers, to indicate which sequence
  // numbers we have already created vertices for.
  typedef pmap<int, EggVertex *> Sequences;
  Sequences _sequences;

  // Get a copy of the list of primitives that reference this vertex.
  // We must have a copy because we will be modifying the list as we
  // traverse it.
  typedef pvector<EggPrimitive *> Prims;
  Prims prims;
  prims.reserve(vert->pref_size());
  copy(vert->pref_begin(), vert->pref_end(), back_inserter(prims));

  // Now walk through the list of primitives that reference this
  // vertex.
  Prims::const_iterator pri;
  for (pri = prims.begin(); pri != prims.end(); ++pri) {
    EggPrimitive *prim = *pri;
    prim->test_ref_count_integrity();

    int seq = sequence(prim);

    if (seq != 0) {
      // Here's a new sequence number!  Have we already defined it?
      EggVertex *new_vert = NULL;

      Sequences::const_iterator si = _sequences.find(seq);

      if (si != _sequences.end()) {
        // Yes, we've seen this sequence number before.  Use the same
        // vertex.
        new_vert = (*si).second;

      } else {
        // No, this is the first time we've encountered this sequence.
        // Split the vertex.
        new_vert = new EggVertex(*vert);
        pool->add_vertex(new_vert);
        _sequences[seq] = new_vert;

        // The new vertex gets all the same group memberships as the
        // old one.
        EggVertex::GroupRef::const_iterator gri;
        for (gri = vert->gref_begin(); gri != vert->gref_end(); ++gri) {
          EggGroup *group = *gri;
          group->ref_vertex(new_vert, group->get_vertex_membership(vert));
        }
      }

      // Now replace the vertex in the primitive.
      EggPrimitive::iterator pi;
      for (pi = prim->begin(); pi != prim->end(); ++pi) {
        if (*pi == vert) {
          prim->replace(pi, new_vert);
        }
      }
    }
  }

#ifndef NDEBUG
  // Now verify everything is still happy.
  vert->test_pref_integrity();
  vert->test_gref_integrity();

  Sequences::const_iterator si;
  for (si = _sequences.begin();
       si != _sequences.end();
       ++si) {
    EggVertex *new_vert = (*si).second;
    new_vert->test_gref_integrity();
    new_vert->test_pref_integrity();
  }
#endif  // NDEBUG

}

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