+
+//================================================================================
+/*!
+ * \brief Find out elements orientation on a geometrical face
+ * \param theFace - The face correctly oriented in the shape being meshed
+ * \param theMeshDS - The mesh data structure
+ * \retval bool - true if the face normal and the normal of first element
+ * in the correspoding submesh point in different directions
+ */
+//================================================================================
+
+bool SMESH_Algo::IsReversedSubMesh (const TopoDS_Face& theFace,
+ SMESHDS_Mesh* theMeshDS)
+{
+ if ( theFace.IsNull() || !theMeshDS )
+ return false;
+
+ // find out orientation of a meshed face
+ int faceID = theMeshDS->ShapeToIndex( theFace );
+ TopoDS_Shape aMeshedFace = theMeshDS->IndexToShape( faceID );
+ bool isReversed = ( theFace.Orientation() != aMeshedFace.Orientation() );
+
+ const SMESHDS_SubMesh * aSubMeshDSFace = theMeshDS->MeshElements( faceID );
+ if ( !aSubMeshDSFace )
+ return isReversed;
+
+ // find element with node located on face and get its normal
+ const SMDS_FacePosition* facePos = 0;
+ int vertexID = 0;
+ gp_Pnt nPnt[3];
+ gp_Vec Ne;
+ bool normalOK = false;
+ SMDS_ElemIteratorPtr iteratorElem = aSubMeshDSFace->GetElements();
+ while ( iteratorElem->more() ) // loop on elements on theFace
+ {
+ const SMDS_MeshElement* elem = iteratorElem->next();
+ if ( elem && elem->NbNodes() > 2 ) {
+ SMDS_ElemIteratorPtr nodesIt = elem->nodesIterator();
+ const SMDS_FacePosition* fPos = 0;
+ int i = 0, vID = 0;
+ while ( nodesIt->more() ) { // loop on nodes
+ const SMDS_MeshNode* node
+ = static_cast<const SMDS_MeshNode *>(nodesIt->next());
+ if ( i == 3 ) i = 2;
+ nPnt[ i++ ].SetCoord( node->X(), node->Y(), node->Z() );
+ // check position
+ const SMDS_PositionPtr& pos = node->GetPosition();
+ if ( !pos ) continue;
+ if ( pos->GetTypeOfPosition() == SMDS_TOP_FACE ) {
+ fPos = dynamic_cast< const SMDS_FacePosition* >( pos.get() );
+ }
+ else if ( pos->GetTypeOfPosition() == SMDS_TOP_VERTEX ) {
+ vID = pos->GetShapeId();
+ }
+ }
+ if ( fPos || ( !normalOK && vID )) {
+ // compute normal
+ gp_Vec v01( nPnt[0], nPnt[1] ), v02( nPnt[0], nPnt[2] );
+ if ( v01.SquareMagnitude() > RealSmall() &&
+ v02.SquareMagnitude() > RealSmall() )
+ {
+ Ne = v01 ^ v02;
+ normalOK = ( Ne.SquareMagnitude() > RealSmall() );
+ }
+ // we need position on theFace or at least on vertex
+ if ( normalOK ) {
+ vertexID = vID;
+ if ((facePos = fPos))
+ break;
+ }
+ }
+ }
+ }
+ if ( !normalOK )
+ return isReversed;
+
+ // node position on face
+ double u,v;
+ if ( facePos ) {
+ u = facePos->GetUParameter();
+ v = facePos->GetVParameter();
+ }
+ else if ( vertexID ) {
+ TopoDS_Shape V = theMeshDS->IndexToShape( vertexID );
+ if ( V.IsNull() || V.ShapeType() != TopAbs_VERTEX )
+ return isReversed;
+ gp_Pnt2d uv = BRep_Tool::Parameters( TopoDS::Vertex( V ), theFace );
+ u = uv.X();
+ v = uv.Y();
+ }
+ else
+ {
+ return isReversed;
+ }
+
+ // face normal at node position
+ TopLoc_Location loc;
+ Handle(Geom_Surface) surf = BRep_Tool::Surface( theFace, loc );
+ if ( surf.IsNull() || surf->Continuity() < GeomAbs_C1 ) return isReversed;
+ gp_Vec d1u, d1v;
+ surf->D1( u, v, nPnt[0], d1u, d1v );
+ gp_Vec Nf = (d1u ^ d1v).Transformed( loc );
+
+ if ( theFace.Orientation() == TopAbs_REVERSED )
+ Nf.Reverse();
+
+ return Ne * Nf < 0.;
+}
