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rAKA/src/model/contact_mechanics/contact_detector.cc
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contact_detector.cc
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/**
* @file contact_detector.cc
*
* @author Mohit Pundir <mohit.pundir@epfl.ch>
*
* @date creation: Wed Sep 12 2018
* @date last modification: Fri Sep 21 2018
*
* @brief Mother class for all detection algorithms
*
* @section LICENSE
*
* Copyright (©) 2010-2018 EPFL (Ecole Polytechnique Fédérale de Lausanne)
* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* Akantu is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* Akantu is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
*
*/
/* -------------------------------------------------------------------------- */
#include "contact_detector.hh"
/* -------------------------------------------------------------------------- */
namespace akantu {
/* -------------------------------------------------------------------------- */
ContactDetector::ContactDetector(Mesh & mesh, const ID & id, UInt memory_id)
: ContactDetector(mesh, mesh.getNodes(), id, memory_id) {
}
/* -------------------------------------------------------------------------- */
ContactDetector::ContactDetector(Mesh & mesh, Array<Real> & positions, const ID & id, UInt memory_id)
: Memory(id, memory_id),
Parsable(ParserType::_contact_detector, id),
mesh(mesh),
positions(positions) {
AKANTU_DEBUG_IN();
this->spatial_dimension = mesh.getSpatialDimension();
this->mesh.fillNodesToElements(this->spatial_dimension - 1);
this->parseSection();
this->getMaximalDetectionDistance();
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void ContactDetector::parseSection() {
const Parser & parser = getStaticParser();
const ParserSection & section =
*(parser.getSubSections(ParserType::_contact_detector).first);
auto type = section.getParameterValue<std::string>("type");
if (type == "implicit") {
this->detection_type = _implicit;
}
else if (type == "explicit"){
this->detection_type = _explicit;
}
else {
AKANTU_ERROR("Unknown detection type : " << type);
}
surfaces[Surface::master] = section.getParameterValue<std::string>("master_surface");
surfaces[Surface::slave ] = section.getParameterValue<std::string>("slave_surface");
}
/* -------------------------------------------------------------------------- */
void ContactDetector::getMaximalDetectionDistance() {
AKANTU_DEBUG_IN();
Real el_size;
Real max_el_size = std::numeric_limits<Real>::min();
auto & master_group =
mesh.getElementGroup(surfaces[Surface::master]);
for (auto & type: master_group.elementTypes(spatial_dimension - 1, _not_ghost)) {
UInt nb_nodes_per_element = mesh.getNbNodesPerElement(type);
Array<Real> coord(0, nb_nodes_per_element * spatial_dimension);
FEEngine::extractNodalToElementField(mesh, mesh.getNodes(), coord, type,
_not_ghost);
auto el_coord = coord.begin(spatial_dimension, nb_nodes_per_element);
UInt nb_element = mesh.getNbElement(type);
for (UInt el =0; el < nb_element; ++el, ++el_coord) {
el_size = FEEngine::getElementInradius(*el_coord, type);
max_el_size = std::max(max_el_size, el_size);
}
AKANTU_DEBUG_INFO("The maximum element size : "
<< max_el_size );
}
this->max_dd = max_el_size;
this->max_bb = max_el_size;
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void ContactDetector::search(std::map<UInt, ContactElement> & contact_map) {
this->globalSearch(contact_map);
}
/* -------------------------------------------------------------------------- */
void ContactDetector::globalSearch(std::map<UInt, ContactElement> & contact_map) {
auto & master_list =
mesh.getElementGroup(surfaces[Surface::master]).getNodeGroup().getNodes();
auto & slave_list =
mesh.getElementGroup(surfaces[Surface::slave]).getNodeGroup().getNodes();
BBox bbox_master(spatial_dimension);
this->constructBoundingBox(bbox_master, master_list);
BBox bbox_slave(spatial_dimension);
this->constructBoundingBox(bbox_slave, slave_list);
auto && bbox_intersection =
bbox_master.intersection(bbox_slave);
AKANTU_DEBUG_INFO( "Intersection BBox "
<< bbox_intersection );
Vector<Real> center(spatial_dimension);
bbox_intersection.getCenter(center);
Vector<Real> spacing(spatial_dimension);
this->computeCellSpacing(spacing);
auto & master_surface_list =
mesh.getElementGroup(surfaces[Surface::master]).getNodeGroup().getNodes();
auto & slave_surface_list =
mesh.getElementGroup(surfaces[Surface::slave]).getNodeGroup().getNodes();
SpatialGrid<UInt> master_grid(spatial_dimension, spacing, center);
this->constructGrid(master_grid, bbox_intersection, master_surface_list);
SpatialGrid<UInt> slave_grid(spatial_dimension, spacing, center);
this->constructGrid(slave_grid, bbox_intersection, slave_surface_list);
if (AKANTU_DEBUG_TEST(dblDump)) {
Mesh mesh(spatial_dimension, "save");
master_grid.saveAsMesh(mesh);
mesh.write("master_grid.msh");
}
if (AKANTU_DEBUG_TEST(dblDump)) {
Mesh mesh2(spatial_dimension, "save");
slave_grid.saveAsMesh(mesh2);
mesh2.write("slave_grid.msh");
}
AKANTU_DEBUG_INFO( "Grid Details " << master_grid );
// search slave grid nodes in contactelement array and if they exits
// and still have orthogonal projection on its associated master
// facetremove it from the spatial grid or do not consider it for
// local search, maybe better option will be to have spatial grid of
// type node info and one of the variable of node info should be
// facet already exits
// so contact eleemnts will be updated based on the above
// consideration , this means only those contact elements will be
// keep whose slave node is still in intersection bbox and still has
// projection in its master facet
// also if slave node is already exists in contact element and
// orthogonal projection does not exits then search the associated
// master facets with the current master facets within a given
// radius , this is subjected to computational cost as searching
// neighbbor cells can be more effective.
this->localSearch(slave_grid, master_grid, contact_map);
}
/* -------------------------------------------------------------------------- */
void ContactDetector::localSearch(SpatialGrid<UInt> & slave_grid,
SpatialGrid<UInt> & master_grid,
std::map<UInt, ContactElement> & contact_map) {
// local search
// out of these array check each cell for closet node in that cell
// and neighbouring cells find the actual orthogonally closet
// check the projection of slave node on master facets connected to
// the closet master node, if yes update the contact element with
// slave node and master node and master surfaces connected to the
// master node
// these master surfaces will be needed later to update contact
// elements
Array<UInt> slave_nodes;
Array<UInt> master_nodes;
BBox bbox_master_grid(spatial_dimension);
BBox bbox_slave_grid(spatial_dimension);
bbox_master_grid += master_grid.getUpperBounds();
bbox_master_grid += master_grid.getLowerBounds();
bbox_slave_grid += slave_grid.getUpperBounds();
bbox_slave_grid += slave_grid.getLowerBounds();
auto && bbox_intersection =
bbox_master_grid.intersection(bbox_slave_grid);
// find the closet master node for each slave node
for (auto && cell_id : slave_grid) {
AKANTU_DEBUG_INFO("Looping on next cell");
for (auto && q1: slave_grid.getCell(cell_id)) {
Vector<Real> pos(spatial_dimension);
for (UInt s: arange(spatial_dimension)) {
pos(s) = this->positions(q1, s);
}
if (!bbox_intersection.contains(pos)) {
continue;
}
Real closet_distance = std::numeric_limits<Real>::max();
UInt closet_master_node;
// loop over all the neighboring cells of the current cells
for (auto && neighbor_cell : cell_id.neighbors()) {
// loop over the data of neighboring cells from master grid
for (auto && q2 : master_grid.getCell(neighbor_cell)) {
AKANTU_DEBUG_INFO("Looping on neighbor cell in master");
Vector<Real> pos2(spatial_dimension);
for (UInt s: arange(spatial_dimension)) {
pos2(s) = this->positions(q2, s);
}
Real distance = pos.distance(pos2);
if (distance <= closet_distance) {
closet_master_node = q2;
closet_distance = distance;
}
}
}
slave_nodes.push_back(q1);
master_nodes.push_back(closet_master_node);
}
}
for (auto && values : zip(slave_nodes, master_nodes)) {
const auto & slave_node = std::get<0>(values);
const auto & master_node = std::get<1>(values);
Array<Element> elements;
this->mesh.getAssociatedElements(master_node, elements);
auto normals = std::make_unique<Array<Real>>(elements.size(),
spatial_dimension, "normals");
auto gaps = std::make_unique<Array<Real>>(elements.size(),
1, "gaps");
auto natural_projections = std::make_unique<Array<Real>>(elements.size(),
spatial_dimension - 1, "projections");
this->computeOrthogonalProjection(slave_node, elements,
*normals, *gaps, *natural_projections);
auto minimum = std::min_element( gaps->begin(), gaps->end());
auto index = std::distance( gaps->begin(), minimum);
Vector<UInt> master_conn =
this->mesh.getConnectivity(elements[index]);
Vector<UInt> elem_conn(master_conn.size() + 1);
elem_conn[0] = slave_node;
for (UInt i = 1; i < elem_conn.size(); ++i) {
elem_conn[i] = master_conn[i-1];
}
contact_map[slave_node] = ContactElement(elements[index]);
contact_map[slave_node].gap = (*gaps)[index];
contact_map[slave_node].normal =
Vector<Real>(normals->begin(spatial_dimension)[index], true);
contact_map[slave_node].projection =
Vector<Real>(natural_projections->begin(spatial_dimension - 1)[index], true);
contact_map[slave_node].connectivity = elem_conn;
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::constructGrid(SpatialGrid<UInt> & grid, BBox & bbox,
const Array<UInt> & nodes_list) {
auto to_grid = [&](UInt node) {
Vector<Real> pos(spatial_dimension);
for (UInt s: arange(spatial_dimension)) {
pos(s) = this->positions(node, s);
}
if (bbox.contains(pos)) {
grid.insert(node, pos);
}
};
std::for_each(nodes_list.begin(), nodes_list.end(), to_grid);
}
/* -------------------------------------------------------------------------- */
void ContactDetector::constructBoundingBox(BBox & bbox, const Array<UInt> & nodes_list) {
auto to_bbox = [&](UInt node) {
Vector<Real> pos(spatial_dimension);
for (UInt s: arange(spatial_dimension)) {
pos(s) = this->positions(node, s);
}
bbox += pos;
};
std::for_each(nodes_list.begin(), nodes_list.end(), to_bbox);
AKANTU_DEBUG_INFO("BBox" << bbox);
auto & lower_bound = bbox.getLowerBounds();
auto & upper_bound = bbox.getUpperBounds();
for (UInt s: arange(spatial_dimension)) {
lower_bound(s) -= this->max_bb;
upper_bound(s) += this->max_bb;
}
AKANTU_DEBUG_INFO("BBox" << bbox);
}
/* -------------------------------------------------------------------------- */
void ContactDetector::computeCellSpacing(Vector<Real> & spacing) {
for (UInt s: arange(spatial_dimension))
spacing(s) = std::sqrt(2.0) * max_dd;
}
/* -------------------------------------------------------------------------- */
void ContactDetector::computeOrthogonalProjection(const UInt & node,
const Array<Element> & elements,
Array<Real> & normals, Array<Real> & gaps,
Array<Real> & natural_projections) {
Vector<Real> query(spatial_dimension);
for (UInt s: arange(spatial_dimension)) {
query(s) = this->positions(node, s);
}
for (auto && values :
zip( elements,
gaps,
make_view(normals , spatial_dimension),
make_view(natural_projections, spatial_dimension - 1))) {
const auto & element = std::get<0>(values);
auto & gap = std::get<1>(values);
auto & normal = std::get<2>(values);
auto & natural_projection = std::get<3>(values);
this->computeNormalOnElement(element, normal);
Vector<Real> real_projection(spatial_dimension);
this->computeProjectionOnElement(element, normal, query,
natural_projection, real_projection);
Vector<Real> distance(spatial_dimension);
distance = query - real_projection;
gap = Math::norm(spatial_dimension, distance.storage());
Vector<Real> direction = distance.normalize();
Real cos_angle = direction.dot(normal);
Real tolerance = 1e-8;
if (std::abs(cos_angle - 1) <= tolerance && detection_type == _explicit) {
gap *= -1;
}
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::computeNormalOnElement(const Element & element, Vector<Real> & normal) {
Matrix<Real> vectors(spatial_dimension, spatial_dimension - 1);
this->vectorsAlongElement(element, vectors);
switch (this->spatial_dimension) {
case 2: {
Math::normal2(vectors.storage(), normal.storage());
break;
}
case 3: {
Math::normal3(vectors(0).storage(), vectors(1).storage(), normal.storage());
break;
}
default: { AKANTU_ERROR("Unknown dimension : " << spatial_dimension); }
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::computeProjectionOnElement(const Element & element,
const Vector<Real> & normal,
const Vector<Real> & query,
Vector<Real> & natural_projection,
Vector<Real> & real_projection) {
UInt nb_nodes_per_element = Mesh::getNbNodesPerElement(element.type);
Matrix<Real> coords(spatial_dimension, nb_nodes_per_element);
this->coordinatesOfElement(element, coords);
Vector<Real> point(coords(0));
Real alpha = (query - point).dot(normal);
real_projection = query - alpha * normal;
// use contains function to check whether projection lies inside
// the element, if yes it is a valid projection otherwise no
// still have to think about what to do if normal exists but
// projection doesnot lie inside the element
bool validity = this->isValidProjection(element, real_projection, natural_projection);
}
/* -------------------------------------------------------------------------- */
bool ContactDetector::isValidProjection(const Element & element, Vector<Real> & real_projection,
Vector<Real> & natural_projection) {
const ElementType & type = element.type;
UInt nb_nodes_per_element = mesh.getNbNodesPerElement(type);
UInt * elem_val = mesh.getConnectivity(type,
_not_ghost).storage();
Matrix<Real> nodes_coord(spatial_dimension, nb_nodes_per_element);
mesh.extractNodalValuesFromElement(this->positions /*mesh.getNodes()*/, nodes_coord.storage(),
elem_val + element.element * nb_nodes_per_element,
nb_nodes_per_element, spatial_dimension);
#define GET_NATURAL_COORDINATE(type) \
ElementClass<type>::inverseMap(real_projection, nodes_coord, natural_projection)
AKANTU_BOOST_ALL_ELEMENT_SWITCH(GET_NATURAL_COORDINATE);
#undef GET_NATURAL_COORDINATE
/*Vector<Real> barycenter(spatial_dimension);
mesh.getBarycenter(element, barycenter);
Real distance = 0;
switch (this->spatial_dimension) {
case 2: {
distance = Math::distance_2d(real_projection.storage(), barycenter.storage());
break;
}
case 3: {
distance = Math::distance_3d(real_projection.storage(), barycenter.storage());
break;
}
default: { AKANTU_ERROR("Unknown dimension : " << spatial_dimension); }
}
if (distance <= max_dd) {
return true;
}*/
return false;
}
/* -------------------------------------------------------------------------- */
void ContactDetector::coordinatesOfElement(const Element & el, Matrix<Real> & coords) {
UInt nb_nodes_per_element = Mesh::getNbNodesPerElement(el.type);
Vector<UInt> connect = mesh.getConnectivity(el.type, _not_ghost)
.begin(nb_nodes_per_element)[el.element];
for (UInt n = 0; n < nb_nodes_per_element; ++n) {
UInt node = connect[n];
for (UInt s: arange(spatial_dimension)) {
coords(s, n) = this->positions(node, s);
}
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::vectorsAlongElement(const Element & el, Matrix<Real> & vectors) {
UInt nb_nodes_per_element = Mesh::getNbNodesPerElement(el.type);
Matrix<Real> coords(spatial_dimension, nb_nodes_per_element);
this->coordinatesOfElement(el, coords);
switch (spatial_dimension) {
case 2: {
vectors(0) = Vector<Real>(coords(1)) - Vector<Real>(coords(0));
break;
}
case 3: {
vectors(0) = Vector<Real>(coords(1)) - Vector<Real>(coords(0));
vectors(1) = Vector<Real>(coords(2)) - Vector<Real>(coords(0));
break;
}
default: { AKANTU_ERROR("Unknown dimension : " << spatial_dimension); }
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::normalProjection(const Element & el, const Vector<Real> & slave_coord,
Vector<Real> & natural_coord, Real & tolerance) {
/*Real fmin;
auto update_fmin = [&fmin, &slave_coord, &node_coords, &natural_coord]() {
Vector<Real> physical_guess_v(physical_guess.storage(), spatial_dimension);
// interpolate on natual coordinate and get physical guess
// compute gradient or jacobian on natural cooordiante
// f = slave_coord - physical_guess;
return fmin;
};
auto closet_point_error = update_fmin();
while (tolerance < closet_point_error) {
// compute gradiend on natural coordinate
// compute second variation of shape function at natural coord
closet_point_error = update_fmin();
}*/
}
} // akantu
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