bmesh_separate.cc

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/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

 
#include "bmesh_separate.hh" /* own include */
 
#include "MEM_guardedalloc.h"
 
#include "BLI_vector.hh"
 
#include "bmesh.hh"
#include "intern/bmesh_structure.hh"
 
void BM_mesh_separate_faces(BMesh *bm, BMFaceFilterFunc filter_fn, void *user_data)
{
  BMFace **faces_array_all = MEM_malloc_arrayN<BMFace *>(bm->totface, __func__);
  /*
   * - Create an array of faces based on 'filter_fn'.
   *   First part of array for match, for non-match.
   *
   * - Enable all vertex tags, then clear all tagged vertices from 'faces_b'.
   *
   * - Loop over 'faces_a', checking each vertex,
   *   splitting out any which aren't tagged (and therefor shared), disabling tags as we go.
   */
 
  BMFace *f;
  BMIter iter;
 
  uint faces_a_len = 0;
  uint faces_b_len = 0;
  {
    int i_a = 0;
    int i_b = bm->totface;
    BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
      faces_array_all[filter_fn(f, user_data) ? i_a++ : --i_b] = f;
    }
    faces_a_len = i_a;
    faces_b_len = bm->totface - i_a;
  }
 
  BMFace **faces_a = faces_array_all;
  BMFace **faces_b = faces_array_all + faces_a_len;
 
  /* Enable for all. */
  BM_mesh_elem_hflag_enable_all(bm, BM_VERT, BM_ELEM_TAG, false);
 
  /* Disable vert tag on faces_b */
  for (uint i = 0; i < faces_b_len; i++) {
    BMLoop *l_iter, *l_first;
    l_iter = l_first = BM_FACE_FIRST_LOOP(faces_b[i]);
    do {
      BM_elem_flag_disable(l_iter->v, BM_ELEM_TAG);
    } while ((l_iter = l_iter->next) != l_first);
  }
 
  blender::Vector<BMLoop *, 128> loop_split;
 
  /* Check shared verts ('faces_a' tag and disable) */
  for (uint i = 0; i < faces_a_len; i++) {
    BMLoop *l_iter, *l_first;
    l_iter = l_first = BM_FACE_FIRST_LOOP(faces_a[i]);
    do {
      if (!BM_elem_flag_test(l_iter->v, BM_ELEM_TAG)) {
        BMVert *v = l_iter->v;
        /* Enable, since we may visit this vertex again on other faces */
        BM_elem_flag_enable(v, BM_ELEM_TAG);
 
        /* We know the vertex is shared, collect all vertices and split them off. */
 
        /* Fill 'loop_split' */
        {
          BMEdge *e_first, *e_iter;
          e_iter = e_first = l_iter->e;
          do {
            if (e_iter->l != nullptr) {
              BMLoop *l_radial_first, *l_radial_iter;
              l_radial_first = l_radial_iter = e_iter->l;
              do {
                if (l_radial_iter->v == v) {
                  if (filter_fn(l_radial_iter->f, user_data)) {
                    loop_split.append(l_radial_iter);
                  }
                }
              } while ((l_radial_iter = l_radial_iter->radial_next) != l_radial_first);
            }
          } while ((e_iter = bmesh_disk_edge_next(e_iter, v)) != e_first);
        }
 
        /* Perform the split */
        BM_face_loop_separate_multi(bm, loop_split.data(), loop_split.size());
 
        loop_split.clear();
      }
    } while ((l_iter = l_iter->next) != l_first);
  }
 
  MEM_freeN(faces_array_all);
}