1 // Copyright (C) 2007-2016 CEA/DEN, EDF R&D, OPEN CASCADE
3 // Copyright (C) 2003-2007 OPEN CASCADE, EADS/CCR, LIP6, CEA/DEN,
4 // CEDRAT, EDF R&D, LEG, PRINCIPIA R&D, BUREAU VERITAS
6 // This library is free software; you can redistribute it and/or
7 // modify it under the terms of the GNU Lesser General Public
8 // License as published by the Free Software Foundation; either
9 // version 2.1 of the License, or (at your option) any later version.
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // Lesser General Public License for more details.
16 // You should have received a copy of the GNU Lesser General Public
17 // License along with this library; if not, write to the Free Software
18 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 // See http://www.salome-platform.org/ or email : webmaster.salome@opencascade.com
22 // File : SMESH_Triangulate.cxx
23 // Created : Thu Jan 18 18:00:13 2018
24 // Author : Edward AGAPOV (eap)
26 // Extracted from ../DriverSTL/DriverSTL_W_SMDS_Mesh.cxx
28 #include "SMESH_MeshAlgos.hxx"
30 #include <Standard_ErrorHandler.hxx>
31 #include <Standard_Failure.hxx>
34 #include <boost/container/flat_set.hpp>
36 using namespace SMESH_MeshAlgos;
40 struct Node // node of a triangle
42 size_t _triaIndex; // triangle index == index of the 1st triangle node in triangulation array
43 size_t _nodeIndex; // node index within triangle [0-2]
45 //! return node index within the node array
46 size_t Index() const { return _triaIndex + _nodeIndex; }
48 //! return local 3-d index [0-2]
49 static size_t ThirdIndex( size_t i1, size_t i2 )
51 size_t i3 = ( i2 + 1 ) % 3;
56 //! return 3-d node index within the node array
57 static size_t ThirdIndex( const Node& n1, const Node& n2 )
59 return n1._triaIndex + ThirdIndex( n1._nodeIndex, n2._nodeIndex );
61 bool operator<(const Node& other) const { return _triaIndex < other._triaIndex; }
63 typedef boost::container::flat_set< Node > TNodeSet;
67 struct Triangulate::Optimizer
69 std::vector< TNodeSet > _nodeUsage; // inclusions of a node in triangles
71 //================================================================================
73 * \brief Optimize triangles by edge swapping
74 * \param [inout] nodes - polygon triangulation, i.e. connectivity of all triangles to optimize
75 * \param [in] points - coordinates of nodes of the input polygon
76 * \param [in] nodeIndices - indices of triangulation nodes within the input polygon
78 //================================================================================
80 void optimize( std::vector< const SMDS_MeshNode*>& nodes,
81 std::vector< PolyVertex > & points,
82 std::vector< size_t > & nodeIndices)
84 // for each node of the polygon, remember triangles using it
85 _nodeUsage.resize( points.size() );
86 for ( size_t i = 0; i < points.size(); ++i ) // clear old data
88 _nodeUsage[ i ].clear();
90 for ( size_t i = 0, iTria = 0; i < nodeIndices.size(); ++iTria )
92 _nodeUsage[ nodeIndices[ i++ ]].insert({ iTria * 3, 0 });
93 _nodeUsage[ nodeIndices[ i++ ]].insert({ iTria * 3, 1 });
94 _nodeUsage[ nodeIndices[ i++ ]].insert({ iTria * 3, 2 });
98 for ( size_t iTria = 0; iTria < nodeIndices.size(); iTria += 3 )
100 double badness1 = computeBadness( nodeIndices[ iTria + 0 ],
101 nodeIndices[ iTria + 1 ],
102 nodeIndices[ iTria + 2 ],
104 for ( size_t i = 0; i < 3; ++i ) // loop on triangle edges to find a neighbor triangle
106 size_t i1 = iTria + i; // node index in nodeIndices
107 size_t i2 = iTria + ( i + 1 ) % 3;
108 size_t ind1 = nodeIndices[ i1 ]; // node index in points
109 size_t ind2 = nodeIndices[ i2 ];
110 TNodeSet & usage1 = _nodeUsage[ ind1 ]; // triangles using a node
111 TNodeSet & usage2 = _nodeUsage[ ind2 ];
112 if ( usage1.size() < 2 ||
116 // look for another triangle using two nodes
117 TNodeSet::iterator usIt1 = usage1.begin();
118 for ( ; usIt1 != usage1.end(); ++usIt1 )
120 if ( usIt1->_triaIndex == iTria )
121 continue; // current triangle
122 TNodeSet::iterator usIt2 = usage2.find( *usIt1 );
123 if ( usIt2 == usage2.end() )
124 continue; // no common _triaIndex in two usages
126 size_t i3 = iTria + ( i + 2 ) % 3;
127 size_t i4 = Node::ThirdIndex( *usIt1, *usIt2 ); // 4th node of quadrangle
128 size_t ind3 = nodeIndices[ i3 ];
129 size_t ind4 = nodeIndices[ i4 ];
131 double badness2 = computeBadness( ind2, ind1, ind4, points );
132 double badness3 = computeBadness( ind1, ind4, ind3, points, /*checkArea=*/true );
133 double badness4 = computeBadness( ind2, ind3, ind4, points, /*checkArea=*/true );
135 if ( Max( badness1, badness2 ) < Max( badness3, badness4 ))
138 // swap edge by modifying nodeIndices
140 nodeIndices[ i2 ] = ind4;
141 _nodeUsage[ ind2 ].erase ({ iTria, i2 - iTria });
142 _nodeUsage[ ind4 ].insert({ iTria, i2 - iTria });
145 nodeIndices[ i1 ] = ind3;
146 _nodeUsage[ ind1 ].erase ( *usIt1 );
147 _nodeUsage[ ind3 ].insert( *usIt1 );
149 --i; // to re-check a current edge
156 // update nodes by updated nodeIndices
157 for ( size_t i = 0; i < nodeIndices.size(); ++i )
158 nodes[ i ] = points[ nodeIndices[ i ]]._nxyz.Node();
163 //================================================================================
165 * \brief Return 1./area. Initially: max cos^2 of triangle angles
167 //================================================================================
169 double computeBadness( size_t i1, size_t i2, size_t i3,
170 std::vector< PolyVertex > & points,
171 bool checkArea = false )
175 points[ i2 ]._prev = & points[ i1 ];
176 points[ i2 ]._next = & points[ i3 ];
177 double a = points[ i2 ].TriaArea();
179 return std::numeric_limits<double>::max();
182 if ( points[ i2 ].TriaArea() < 0 )
185 const gp_XY & p1 = points[ i1 ]._xy;
186 const gp_XY & p2 = points[ i2 ]._xy;
187 const gp_XY & p3 = points[ i3 ]._xy;
188 gp_XY vec[3] = { p2 - p1,
191 double len[3] = { vec[0].SquareModulus(),
192 vec[1].SquareModulus(),
193 vec[2].SquareModulus() };
194 if ( len[0] < gp::Resolution() ||
195 len[1] < gp::Resolution() ||
196 len[2] < gp::Resolution() )
200 for ( int i = 0; i < 3; ++i )
202 int i2 = ( i+1 ) % 3;
203 double dot = -vec[ i ] * vec[ i2 ];
205 maxCos2 = Max( maxCos2, dot * dot / len[ i ] / len[ i2 ] );
211 //================================================================================
213 * \brief Initialization
215 //================================================================================
217 void Triangulate::PolyVertex::SetNodeAndNext( const SMDS_MeshNode* n,
226 //================================================================================
228 * \brief Remove self from a polygon
230 //================================================================================
232 Triangulate::PolyVertex* Triangulate::PolyVertex::Delete()
234 _prev->_next = _next;
235 _next->_prev = _prev;
239 //================================================================================
241 * \brief Return nodes of a triangle
243 //================================================================================
245 void Triangulate::PolyVertex::GetTriaNodes( const SMDS_MeshNode** nodes,
246 size_t* nodeIndices) const
248 nodes[0] = _prev->_nxyz._node;
249 nodes[1] = this->_nxyz._node;
250 nodes[2] = _next->_nxyz._node;
251 nodeIndices[0] = _prev->_index;
252 nodeIndices[1] = this->_index;
253 nodeIndices[2] = _next->_index;
256 //================================================================================
258 * \brief Compute triangle area
260 //================================================================================
262 inline static double Area( const gp_XY& xy0, const gp_XY& xy1, const gp_XY& xy2 )
264 gp_XY vPrev = xy0 - xy1;
265 gp_XY vNext = xy2 - xy1;
266 return vNext ^ vPrev;
269 //================================================================================
271 * \brief Compute triangle area
273 //================================================================================
275 double Triangulate::PolyVertex::TriaArea() const
277 return Area( _prev->_xy, this->_xy, _next->_xy );
280 //================================================================================
282 * \brief Check if a vertex is inside a triangle
284 //================================================================================
286 bool Triangulate::PolyVertex::IsInsideTria( const PolyVertex* v )
288 if ( this ->_nxyz == v->_nxyz ||
289 _prev->_nxyz == v->_nxyz ||
290 _next->_nxyz == v->_nxyz )
293 gp_XY p = _prev->_xy - v->_xy;
294 gp_XY t = this->_xy - v->_xy;
295 gp_XY n = _next->_xy - v->_xy;
296 const double tol = -1e-7;
297 return (( p ^ t ) >= tol &&
300 // return ( Area( _prev, this, v ) > 0 &&
301 // Area( this, _next, v ) > 0 &&
302 // Area( _next, _prev, v ) > 0 );
305 //================================================================================
307 * \brief Triangulate a polygon. Assure correct orientation for concave polygons
309 //================================================================================
311 bool Triangulate::triangulate( std::vector< const SMDS_MeshNode*>& nodes,
312 const size_t nbNodes)
314 // connect nodes into a ring
315 _pv.resize( nbNodes );
316 for ( size_t i = 1; i < nbNodes; ++i )
317 _pv[i-1].SetNodeAndNext( nodes[i-1], _pv[i], i-1 );
318 _pv[ nbNodes-1 ].SetNodeAndNext( nodes[ nbNodes-1 ], _pv[0], nbNodes-1 );
320 // get a polygon normal
321 gp_XYZ normal(0,0,0), p0,v01,v02;
323 v01 = _pv[1]._nxyz - p0;
324 for ( size_t i = 2; i < nbNodes; ++i )
326 v02 = _pv[i]._nxyz - p0;
330 // project nodes to the found plane
333 axes = gp_Ax2( p0, normal, v01 );
335 catch ( Standard_Failure ) {
338 for ( size_t i = 0; i < nbNodes; ++i )
340 gp_XYZ p = _pv[i]._nxyz - p0;
341 _pv[i]._xy.SetX( axes.XDirection().XYZ() * p );
342 _pv[i]._xy.SetY( axes.YDirection().XYZ() * p );
345 // in a loop, find triangles with positive area and having no vertices inside
346 int iN = 0, nbTria = nbNodes - 2;
347 nodes.resize( nbTria * 3 );
348 _nodeIndex.resize( nbTria * 3 );
349 const double minArea = 1e-6;
350 PolyVertex* v = &_pv[0], *vi;
351 int nbVertices = nbNodes, nbBadTria = 0, isGoodTria;
352 while ( nbBadTria < nbVertices )
354 if (( isGoodTria = v->TriaArea() > minArea ))
356 for ( vi = v->_next->_next;
360 if ( v->IsInsideTria( vi ))
363 isGoodTria = ( vi == v->_prev );
367 v->GetTriaNodes( &nodes[ iN ], &_nodeIndex[ iN ] );
370 if ( --nbVertices == 3 )
372 // last triangle remains
373 v->GetTriaNodes( &nodes[ iN ], &_nodeIndex[ iN ] );
375 _optimizer->optimize( nodes, _pv, _nodeIndex );
387 // the polygon is invalid; add triangles with positive area
389 while ( nbBadTria < nbVertices )
391 isGoodTria = v->TriaArea() > minArea;
394 v->GetTriaNodes( &nodes[ iN ], &_nodeIndex[ iN ] );
397 if ( --nbVertices == 3 )
399 // last triangle remains
400 v->GetTriaNodes( &nodes[ iN ], &_nodeIndex[ iN ] );
412 // add all the rest triangles
413 while ( nbVertices >= 3 )
415 v->GetTriaNodes( &nodes[ iN ], &_nodeIndex[ iN ] );
425 //================================================================================
429 //================================================================================
431 Triangulate::Triangulate( bool optimize ): _optimizer(0)
434 _optimizer = new Optimizer;
437 //================================================================================
441 //================================================================================
443 Triangulate::~Triangulate()
449 //================================================================================
451 * \brief Return nb triangles in a decomposed mesh face
452 * \retval int - number of triangles
454 //================================================================================
456 int Triangulate::GetNbTriangles( const SMDS_MeshElement* face )
458 // WARNING: counting triangles must be coherent with GetTriangles()
459 switch ( face->GetEntityType() )
461 case SMDSEntity_BiQuad_Triangle:
462 case SMDSEntity_BiQuad_Quadrangle:
463 return face->NbNodes() - 1;
464 // case SMDSEntity_Triangle:
465 // case SMDSEntity_Quad_Triangle:
466 // case SMDSEntity_Quadrangle:
467 // case SMDSEntity_Quad_Quadrangle:
468 // case SMDSEntity_Polygon:
469 // case SMDSEntity_Quad_Polygon:
471 return face->NbNodes() - 2;
476 //================================================================================
478 * \brief Decompose a mesh face into triangles
479 * \retval int - number of triangles
481 //================================================================================
483 int Triangulate::GetTriangles( const SMDS_MeshElement* face,
484 std::vector< const SMDS_MeshNode*>& nodes)
486 if ( face->GetType() != SMDSAbs_Face )
489 // WARNING: decomposing into triangles must be coherent with getNbTriangles()
490 int nbTria, i = 0, nbNodes = face->NbNodes();
491 SMDS_NodeIteratorPtr nIt = face->interlacedNodesIterator();
492 nodes.resize( nbNodes * 3 );
493 nodes[ i++ ] = nIt->next();
494 nodes[ i++ ] = nIt->next();
496 const SMDSAbs_EntityType type = face->GetEntityType();
499 case SMDSEntity_BiQuad_Triangle:
500 case SMDSEntity_BiQuad_Quadrangle:
502 nbTria = ( type == SMDSEntity_BiQuad_Triangle ) ? 6 : 8;
503 nodes[ i++ ] = face->GetNode( nbTria );
504 for ( i = 3; i < 3*(nbTria-1); i += 3 )
506 nodes[ i+0 ] = nodes[ i-2 ];
507 nodes[ i+1 ] = nIt->next();
508 nodes[ i+2 ] = nodes[ 2 ];
510 nodes[ i+0 ] = nodes[ i-2 ];
511 nodes[ i+1 ] = nodes[ 0 ];
512 nodes[ i+2 ] = nodes[ 2 ];
515 case SMDSEntity_Triangle:
518 nodes[ i++ ] = nIt->next();
523 // case SMDSEntity_Quad_Triangle:
524 // case SMDSEntity_Quadrangle:
525 // case SMDSEntity_Quad_Quadrangle:
526 // case SMDSEntity_Polygon:
527 // case SMDSEntity_Quad_Polygon:
529 nbTria = nbNodes - 2;
530 while ( nIt->more() )
531 nodes[ i++ ] = nIt->next();
533 if ( nbTria > 1 && !triangulate( nodes, nbNodes ))
535 nIt = face->interlacedNodesIterator();
536 nodes[ 0 ] = nIt->next();
537 nodes[ 1 ] = nIt->next();
538 nodes[ 2 ] = nIt->next();
539 for ( i = 3; i < 3*nbTria; i += 3 )
541 nodes[ i+0 ] = nodes[ 0 ];
542 nodes[ i+1 ] = nodes[ i-1 ];
543 nodes[ i+2 ] = nIt->next();