bool ElemCutter::is_outside (const Elem &elem,
const std::vector<Real> &vertex_distance_func) const
{
libmesh_assert_equal_to (elem.n_vertices(), vertex_distance_func.size());
for (std::vector<Real>::const_iterator it=vertex_distance_func.begin();
it!=vertex_distance_func.end(); ++it)
if (*it < 0.) return false;
// if the distance function is nonnegative, we are outside
return true;
}
void QComposite<QSubCell>::init (const Elem &elem,
const std::vector<Real> &vertex_distance_func,
unsigned int p_level)
{
libmesh_assert_equal_to (vertex_distance_func.size(), elem.n_vertices());
libmesh_assert_equal_to (_dim, elem.dim());
// if we are not cut, revert to simple base class init() method.
if (!_elem_cutter.is_cut (elem, vertex_distance_func))
{
_q_subcell.init (elem.type(), p_level);
_points = _q_subcell.get_points();
_weights = _q_subcell.get_weights();
//this->print_info();
return;
}
// Get a pointer to the element's reference element. We want to
// perform cutting on the reference element such that the quadrature
// point locations of the subelements live in the reference
// coordinate system, thereby eliminating the need for inverse
// mapping.
const Elem *reference_elem = elem.reference_elem();
libmesh_assert (reference_elem != NULL);
_elem_cutter(*reference_elem, vertex_distance_func);
//_elem_cutter(elem, vertex_distance_func);
// clear our state & accumulate points from subelements
_points.clear();
_weights.clear();
// inside subelem
{
const std::vector<Elem const*> &inside_elem (_elem_cutter.inside_elements());
std::cout << inside_elem.size() << " elements inside\n";
this->add_subelem_values(inside_elem);
}
// outside subelem
{
const std::vector<Elem const*> &outside_elem (_elem_cutter.outside_elements());
std::cout << outside_elem.size() << " elements outside\n";
this->add_subelem_values(outside_elem);
}
this->print_info();
}
bool ElemCutter::is_cut (const Elem &elem,
const std::vector<Real> &vertex_distance_func) const
{
libmesh_assert_equal_to (elem.n_vertices(), vertex_distance_func.size());
Real
vmin = vertex_distance_func.front(),
vmax = vmin;
for (std::vector<Real>::const_iterator it=vertex_distance_func.begin();
it!=vertex_distance_func.end(); ++it)
{
vmin = std::min (vmin, *it);
vmax = std::max (vmax, *it);
}
// if the distance function changes sign, we're cut.
return (vmin*vmax < 0.);
}
void ElemCutter::operator()(const Elem & elem,
const std::vector<Real> & vertex_distance_func)
{
libmesh_assert_equal_to (vertex_distance_func.size(), elem.n_vertices());
_inside_elem.clear();
_outside_elem.clear();
// check for quick return?
{
// completely outside?
if (this->is_outside(elem, vertex_distance_func))
{
//std::cout << "element completely outside\n";
_outside_elem.push_back(& elem);
return;
}
// completely inside?
else if (this->is_inside(elem, vertex_distance_func))
{
//std::cout << "element completely inside\n";
_inside_elem.push_back(&elem);
return;
}
libmesh_assert (this->is_cut (elem, vertex_distance_func));
}
// we now know we are in a cut element, find the intersecting points.
this->find_intersection_points (elem, vertex_distance_func);
// and then dispatch the proper method
switch (elem.dim())
{
case 1: this->cut_1D(elem, vertex_distance_func); break;
case 2: this->cut_2D(elem, vertex_distance_func); break;
case 3: this->cut_3D(elem, vertex_distance_func); break;
default: libmesh_error_msg("Invalid element dimension: " << elem.dim());
}
}
void ElemCutter::cut_3D (const Elem & elem,
const std::vector<Real> & vertex_distance_func)
{
#ifndef LIBMESH_HAVE_TETGEN
// current implementation requires tetgen!
libMesh::err << "ERROR: current libMesh ElemCutter 3D implementation requires\n"
<< " the \"tetgen\" library!\n"
<< std::endl;
libmesh_not_implemented();
#else // OK, LIBMESH_HAVE_TETGEN
std::cout << "Inside cut cell element!\n";
libmesh_assert (_inside_mesh_3D.get() != nullptr);
libmesh_assert (_outside_mesh_3D.get() != nullptr);
_inside_mesh_3D->clear();
_outside_mesh_3D->clear();
for (unsigned int v=0; v<elem.n_vertices(); v++)
{
if (vertex_distance_func[v] >= 0.)
_outside_mesh_3D->add_point (elem.point(v));
if (vertex_distance_func[v] <= 0.)
_inside_mesh_3D->add_point (elem.point(v));
}
for (const auto & pt : _intersection_pts)
{
_inside_mesh_3D->add_point(pt);
_outside_mesh_3D->add_point(pt);
}
// Triangulate!
_tetgen_inside->triangulate_pointset();
//_inside_mesh_3D->print_info();
_tetgen_outside->triangulate_pointset();
//_outside_mesh_3D->print_info();
// (below generates some horribly expensive meshes,
// but seems immune to the 0 volume problem).
// _tetgen_inside->pointset_convexhull();
// _inside_mesh_3D->find_neighbors();
// _inside_mesh_3D->print_info();
// _tetgen_inside->triangulate_conformingDelaunayMesh (1.e3, 100.);
// _inside_mesh_3D->print_info();
// _tetgen_outside->pointset_convexhull();
// _outside_mesh_3D->find_neighbors();
// _outside_mesh_3D->print_info();
// _tetgen_outside->triangulate_conformingDelaunayMesh (1.e3, 100.);
// _outside_mesh_3D->print_info();
std::ostringstream name;
name << "cut_cell_"
<< cut_cntr++
<< ".dat";
_inside_mesh_3D->write ("in_" + name.str());
_outside_mesh_3D->write ("out_" + name.str());
// finally, add the elements to our lists.
_inside_elem.clear();
_outside_elem.clear();
for (const auto & elem : _inside_mesh_3D->element_ptr_range())
if (elem->volume() > std::numeric_limits<Real>::epsilon())
_inside_elem.push_back (elem);
for (const auto & elem : _outside_mesh_3D->element_ptr_range())
if (elem->volume() > std::numeric_limits<Real>::epsilon())
_outside_elem.push_back (elem);
#endif
}
void ElemCutter::cut_2D (const Elem & elem,
const std::vector<Real> & vertex_distance_func)
{
#ifndef LIBMESH_HAVE_TRIANGLE
// current implementation requires triangle!
libMesh::err << "ERROR: current libMesh ElemCutter 2D implementation requires\n"
<< " the \"triangle\" library!\n"
<< std::endl;
libmesh_not_implemented();
#else // OK, LIBMESH_HAVE_TRIANGLE
std::cout << "Inside cut face element!\n";
libmesh_assert (_inside_mesh_2D.get() != nullptr);
libmesh_assert (_outside_mesh_2D.get() != nullptr);
_inside_mesh_2D->clear();
_outside_mesh_2D->clear();
for (unsigned int v=0; v<elem.n_vertices(); v++)
{
if (vertex_distance_func[v] >= 0.)
_outside_mesh_2D->add_point (elem.point(v));
if (vertex_distance_func[v] <= 0.)
_inside_mesh_2D->add_point (elem.point(v));
}
for (const auto & pt : _intersection_pts)
{
_inside_mesh_2D->add_point(pt);
_outside_mesh_2D->add_point(pt);
}
// Customize the variables for the triangulation
// we will be cutting reference cell, and want as few triangles
// as possible, so jack this up larger than the area we will be
// triangulating so we are governed only by accurately defining
// the boundaries.
_triangle_inside->desired_area() = 100.;
_triangle_outside->desired_area() = 100.;
// allow for small angles
_triangle_inside->minimum_angle() = 5.;
_triangle_outside->minimum_angle() = 5.;
// Turn off Laplacian mesh smoothing after generation.
_triangle_inside->smooth_after_generating() = false;
_triangle_outside->smooth_after_generating() = false;
// Triangulate!
_triangle_inside->triangulate();
_triangle_outside->triangulate();
// std::ostringstream name;
// name << "cut_face_"
// << cut_cntr++
// << ".dat";
// _inside_mesh_2D->write ("in_" + name.str());
// _outside_mesh_2D->write ("out_" + name.str());
// finally, add the elements to our lists.
_inside_elem.clear();
_outside_elem.clear();
for (const auto & elem : _inside_mesh_2D->element_ptr_range())
_inside_elem.push_back (elem);
for (const auto & elem : _outside_mesh_2D->element_ptr_range())
_outside_elem.push_back (elem);
#endif
}
void MeshBase::detect_interior_parents()
{
// This requires an inspection on every processor
parallel_object_only();
// Check if the mesh contains mixed dimensions. If so, then set interior parents, otherwise return.
if (this->elem_dimensions().size() == 1)
return;
//This map will be used to set interior parents
LIBMESH_BEST_UNORDERED_MAP<dof_id_type, std::vector<dof_id_type> > node_to_elem;
const_element_iterator el = this->active_elements_begin();
const_element_iterator end = this->active_elements_end();
for (; el!=end; ++el)
{
const Elem * elem = *el;
// Populating the node_to_elem map, same as MeshTools::build_nodes_to_elem_map
for (unsigned int n=0; n<elem->n_vertices(); n++)
{
libmesh_assert_less (elem->id(), this->max_elem_id());
node_to_elem[elem->node(n)].push_back(elem->id());
}
}
// Automatically set interior parents
el = this->elements_begin();
for (; el!=end; ++el)
{
Elem * element = *el;
// Ignore an 3D element or an element that already has an interior parent
if (element->dim()>=LIBMESH_DIM || element->interior_parent())
continue;
// Start by generating a SET of elements that are dim+1 to the current
// element at each vertex of the current element, thus ignoring interior nodes.
// If one of the SET of elements is empty, then we will not have an interior parent
// since an interior parent must be connected to all vertices of the current element
std::vector< std::set<dof_id_type> > neighbors( element->n_vertices() );
bool found_interior_parents = false;
for (dof_id_type n=0; n < element->n_vertices(); n++)
{
std::vector<dof_id_type> & element_ids = node_to_elem[element->node(n)];
for (std::vector<dof_id_type>::iterator e_it = element_ids.begin();
e_it != element_ids.end(); e_it++)
{
dof_id_type eid = *e_it;
if (this->elem(eid)->dim() == element->dim()+1)
neighbors[n].insert(eid);
}
if (neighbors[n].size()>0)
{
found_interior_parents = true;
}
else
{
// We have found an empty set, no reason to continue
// Ensure we set this flag to false before the break since it could have
// been set to true for previous vertex
found_interior_parents = false;
break;
}
}
// If we have successfully generated a set of elements for each vertex, we will compare
// the set for vertex 0 will the sets for the vertices until we find a id that exists in
// all sets. If found, this is our an interior parent id. The interior parent id found
// will be the lowest element id if there is potential for multiple interior parents.
if (found_interior_parents)
{
std::set<dof_id_type> & neighbors_0 = neighbors[0];
for (std::set<dof_id_type>::iterator e_it = neighbors_0.begin();
e_it != neighbors_0.end(); e_it++)
{
found_interior_parents=false;
dof_id_type interior_parent_id = *e_it;
for (dof_id_type n=1; n < element->n_vertices(); n++)
{
if (neighbors[n].find(interior_parent_id)!=neighbors[n].end())
{
found_interior_parents=true;
}
else
{
found_interior_parents=false;
break;
}
}
if (found_interior_parents)
{
element->set_interior_parent(this->elem(interior_parent_id));
break;
}
}
}
}
}
// The actual implementation of building elements.
void InfElemBuilder::build_inf_elem(const Point& origin,
const bool x_sym,
const bool y_sym,
const bool z_sym,
const bool be_verbose,
std::set< std::pair<dof_id_type,
unsigned int> >* inner_faces)
{
if (be_verbose)
{
#ifdef DEBUG
libMesh::out << " Building Infinite Elements:" << std::endl;
libMesh::out << " updating element neighbor tables..." << std::endl;
#else
libMesh::out << " Verbose mode disabled in non-debug mode." << std::endl;
#endif
}
// update element neighbors
this->_mesh.find_neighbors();
START_LOG("build_inf_elem()", "InfElemBuilder");
// A set for storing element number, side number pairs.
// pair.first == element number, pair.second == side number
std::set< std::pair<dof_id_type,unsigned int> > faces;
std::set< std::pair<dof_id_type,unsigned int> > ofaces;
// A set for storing node numbers on the outer faces.
std::set<dof_id_type> onodes;
// The distance to the farthest point in the mesh from the origin
Real max_r=0.;
// The index of the farthest point in the mesh from the origin
int max_r_node = -1;
#ifdef DEBUG
if (be_verbose)
{
libMesh::out << " collecting boundary sides";
if (x_sym || y_sym || z_sym)
libMesh::out << ", skipping sides in symmetry planes..." << std::endl;
else
libMesh::out << "..." << std::endl;
}
#endif
// Iterate through all elements and sides, collect indices of all active
// boundary sides in the faces set. Skip sides which lie in symmetry planes.
// Later, sides of the inner boundary will be sorted out.
{
MeshBase::element_iterator it = this->_mesh.active_elements_begin();
const MeshBase::element_iterator end = this->_mesh.active_elements_end();
for(; it != end; ++it)
{
Elem* elem = *it;
for (unsigned int s=0; s<elem->n_neighbors(); s++)
{
// check if elem(e) is on the boundary
if (elem->neighbor(s) == NULL)
{
// note that it is safe to use the Elem::side() method,
// which gives a non-full-ordered element
AutoPtr<Elem> side(elem->build_side(s));
// bool flags for symmetry detection
bool sym_side=false;
bool on_x_sym=true;
bool on_y_sym=true;
bool on_z_sym=true;
// Loop over the nodes to check whether they are on the symmetry planes,
// and therefore sufficient to use a non-full-ordered side element
for(unsigned int n=0; n<side->n_nodes(); n++)
{
const Point dist_from_origin = this->_mesh.point(side->node(n)) - origin;
if(x_sym)
if( std::abs(dist_from_origin(0)) > 1.e-3 )
on_x_sym=false;
if(y_sym)
if( std::abs(dist_from_origin(1)) > 1.e-3 )
on_y_sym=false;
if(z_sym)
if( std::abs(dist_from_origin(2)) > 1.e-3 )
on_z_sym=false;
// if(x_sym)
// if( std::abs(dist_from_origin(0)) > 1.e-6 )
// on_x_sym=false;
// if(y_sym)
// if( std::abs(dist_from_origin(1)) > 1.e-6 )
// on_y_sym=false;
// if(z_sym)
// if( std::abs(dist_from_origin(2)) > 1.e-6 )
// on_z_sym=false;
//find the node most distant from origin
Real r = dist_from_origin.size();
if (r > max_r)
{
max_r = r;
max_r_node=side->node(n);
}
}
sym_side = (x_sym && on_x_sym) || (y_sym && on_y_sym) || (z_sym && on_z_sym);
if (!sym_side)
faces.insert( std::make_pair(elem->id(), s) );
} // neighbor(s) == NULL
} // sides
} // elems
}
// If a boundary side has one node on the outer boundary,
// all points of this side are on the outer boundary.
// Start with the node most distant from origin, which has
// to be on the outer boundary, then recursively find all
// sides and nodes connected to it. Found sides are moved
// from faces to ofaces, nodes are collected in onodes.
// Here, the search is done iteratively, because, depending on
// the mesh, a very high level of recursion might be necessary.
if (max_r_node > 0)
onodes.insert(max_r_node);
{
std::set< std::pair<dof_id_type,unsigned int> >::iterator face_it = faces.begin();
unsigned int facesfound=0;
while (face_it != faces.end()) {
std::pair<dof_id_type, unsigned int> p;
p = *face_it;
// This has to be a full-ordered side element,
// since we need the correct n_nodes,
AutoPtr<Elem> side(this->_mesh.elem(p.first)->build_side(p.second));
bool found=false;
for(unsigned int sn=0; sn<side->n_nodes(); sn++)
if(onodes.count(side->node(sn)))
{
found=true;
break;
}
// If a new oface is found, include its nodes in onodes
if(found)
{
for(unsigned int sn=0; sn<side->n_nodes(); sn++)
onodes.insert(side->node(sn));
ofaces.insert(p);
face_it++; // iteration is done here
faces.erase(p);
facesfound++;
}
else
face_it++; // iteration is done here
// If at least one new oface was found in this cycle,
// do another search cycle.
if(facesfound>0 && face_it == faces.end())
{
facesfound = 0;
face_it = faces.begin();
}
}
}
#ifdef DEBUG
if (be_verbose)
libMesh::out << " found "
<< faces.size()
<< " inner and "
<< ofaces.size()
<< " outer boundary faces"
<< std::endl;
#endif
// When the user provided a non-null pointer to
// inner_faces, that implies he wants to have
// this std::set. For now, simply copy the data.
if (inner_faces != NULL)
*inner_faces = faces;
// free memory, clear our local variable, no need
// for it any more.
faces.clear();
// outer_nodes maps onodes to their duplicates
std::map<dof_id_type, Node *> outer_nodes;
// We may need to pick our own object ids in parallel
dof_id_type old_max_node_id = _mesh.max_node_id();
dof_id_type old_max_elem_id = _mesh.max_elem_id();
// for each boundary node, add an outer_node with
// double distance from origin.
std::set<dof_id_type>::iterator on_it = onodes.begin();
for( ; on_it != onodes.end(); ++on_it)
{
Point p = (Point(this->_mesh.point(*on_it)) * 2) - origin;
if (_mesh.is_serial())
{
// Add with a default id in serial
outer_nodes[*on_it]=this->_mesh.add_point(p);
}
else
{
// Pick a unique id in parallel
Node &bnode = _mesh.node(*on_it);
dof_id_type new_id = bnode.id() + old_max_node_id;
outer_nodes[*on_it] =
this->_mesh.add_point(p, new_id,
bnode.processor_id());
}
}
#ifdef DEBUG
// for verbose, remember n_elem
dof_id_type n_conventional_elem = this->_mesh.n_elem();
#endif
// build Elems based on boundary side type
std::set< std::pair<dof_id_type,unsigned int> >::iterator face_it = ofaces.begin();
for( ; face_it != ofaces.end(); ++face_it)
{
// Shortcut to the pair being iterated over
std::pair<dof_id_type,unsigned int> p = *face_it;
// build a full-ordered side element to get the base nodes
AutoPtr<Elem> side(this->_mesh.elem(p.first)->build_side(p.second));
// create cell depending on side type, assign nodes,
// use braces to force scope.
bool is_higher_order_elem = false;
{
Elem* el;
switch(side->type())
{
// 3D infinite elements
// TRIs
case TRI3:
el=new InfPrism6;
break;
case TRI6:
el=new InfPrism12;
is_higher_order_elem = true;
break;
// QUADs
case QUAD4:
el=new InfHex8;
break;
case QUAD8:
el=new InfHex16;
is_higher_order_elem = true;
break;
case QUAD9:
el=new InfHex18;
// the method of assigning nodes (which follows below)
// omits in the case of QUAD9 the bubble node; therefore
// we assign these first by hand here.
el->set_node(16) = side->get_node(8);
el->set_node(17) = outer_nodes[side->node(8)];
is_higher_order_elem=true;
break;
// 2D infinite elements
case EDGE2:
el=new InfQuad4;
break;
case EDGE3:
el=new InfQuad6;
el->set_node(4) = side->get_node(2);
break;
// 1D infinite elements not supported
default:
libMesh::out << "InfElemBuilder::build_inf_elem(Point, bool, bool, bool, bool): "
<< "invalid face element "
<< std::endl;
continue;
}
// In parallel, assign unique ids to the new element
if (!_mesh.is_serial())
{
Elem *belem = _mesh.elem(p.first);
el->processor_id() = belem->processor_id();
// We'd better not have elements with more than 6 sides
el->set_id (belem->id() * 6 + p.second + old_max_elem_id);
}
// assign vertices to the new infinite element
const unsigned int n_base_vertices = side->n_vertices();
for(unsigned int i=0; i<n_base_vertices; i++)
{
el->set_node(i ) = side->get_node(i);
el->set_node(i+n_base_vertices) = outer_nodes[side->node(i)];
}
// when this is a higher order element,
// assign also the nodes in between
if (is_higher_order_elem)
{
// n_safe_base_nodes is the number of nodes in \p side
// that may be safely assigned using below for loop.
// Actually, n_safe_base_nodes is _identical_ with el->n_vertices(),
// since for QUAD9, the 9th node was already assigned above
const unsigned int n_safe_base_nodes = el->n_vertices();
for(unsigned int i=n_base_vertices; i<n_safe_base_nodes; i++)
{
el->set_node(i+n_base_vertices) = side->get_node(i);
el->set_node(i+n_safe_base_nodes) = outer_nodes[side->node(i)];
}
}
// add infinite element to mesh
this->_mesh.add_elem(el);
} // el goes out of scope
} // for
#ifdef DEBUG
_mesh.libmesh_assert_valid_parallel_ids();
if (be_verbose)
libMesh::out << " added "
<< this->_mesh.n_elem() - n_conventional_elem
<< " infinite elements and "
<< onodes.size()
<< " nodes to the mesh"
<< std::endl
<< std::endl;
#endif
STOP_LOG("build_inf_elem()", "InfElemBuilder");
}
