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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 Dec 05 2018
* @date last modification: Thu Jun 24 2021
*
* @brief Mother class for all detection algorithms
*
*
* @section LICENSE
*
* Copyright (©) 2018-2021 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)
: ContactDetector(mesh, mesh.getNodes(), id) {}
/* -------------------------------------------------------------------------- */
ContactDetector::ContactDetector(Mesh & mesh, Array<Real> positions,
const ID & id)
: Parsable(ParserType::_contact_detector, id), mesh(mesh),
positions(0, mesh.getSpatialDimension()) {
AKANTU_DEBUG_IN();
this->spatial_dimension = mesh.getSpatialDimension();
this->positions.copy(positions);
const Parser & parser = getStaticParser();
const ParserSection & section =
*(parser.getSubSections(ParserType::_contact_detector).first);
this->parseSection(section);
AKANTU_DEBUG_OUT();
}
/* -------------------------------------------------------------------------- */
void ContactDetector::parseSection(const ParserSection & section) {
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);
}
this->projection_tolerance =
section.getParameterValue<Real>("projection_tolerance");
this->max_iterations = section.getParameterValue<Real>("max_iterations");
this->extension_tolerance =
section.getParameterValue<Real>("extension_tolerance");
}
/* -------------------------------------------------------------------------- */
void ContactDetector::search(Array<ContactElement> & elements,
Array<Real> & gaps, Array<Real> & normals,
Array<Real> & tangents,
Array<Real> & projections) {
auto surface_dimension = spatial_dimension - 1;
this->mesh.fillNodesToElements(surface_dimension);
this->computeMaximalDetectionDistance();
contact_pairs.clear();
SpatialGrid<UInt> master_grid(spatial_dimension);
SpatialGrid<UInt> slave_grid(spatial_dimension);
this->globalSearch(slave_grid, master_grid);
this->localSearch(slave_grid, master_grid);
this->createContactElements(elements, gaps, normals, tangents, projections);
}
/* -------------------------------------------------------------------------- */
void ContactDetector::globalSearch(SpatialGrid<UInt> & slave_grid,
SpatialGrid<UInt> & master_grid) {
auto & master_list = surface_selector->getMasterList();
auto & slave_list = surface_selector->getSlaveList();
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);
master_grid.setCenter(center);
master_grid.setSpacing(spacing);
this->constructGrid(master_grid, bbox_intersection, master_list);
slave_grid.setCenter(center);
slave_grid.setSpacing(spacing);
this->constructGrid(slave_grid, bbox_intersection, slave_list);
// 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 elements 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.
}
/* -------------------------------------------------------------------------- */
void ContactDetector::localSearch(SpatialGrid<UInt> & slave_grid,
SpatialGrid<UInt> & master_grid) {
// 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
/// find the closet master node for each slave node
for (auto && cell_id : slave_grid) {
/// loop over all the slave nodes of the current cell
for (auto && slave_node : slave_grid.getCell(cell_id)) {
bool pair_exists = false;
Vector<Real> pos(spatial_dimension);
for (UInt s : arange(spatial_dimension)) {
pos(s) = this->positions(slave_node, s);
}
Real closet_distance = std::numeric_limits<Real>::max();
UInt closet_master_node;
/// loop over all the neighboring cells of the current cell
for (auto && neighbor_cell : cell_id.neighbors()) {
/// loop over the data of neighboring cells from master grid
for (auto && master_node : master_grid.getCell(neighbor_cell)) {
/// check for self contact
if (slave_node == master_node) {
continue;
}
bool is_valid = true;
Array<Element> elements;
this->mesh.getAssociatedElements(slave_node, elements);
for (auto & elem : elements) {
if (elem.kind() != _ek_regular) {
continue;
}
Vector<UInt> connectivity =
const_cast<const Mesh &>(this->mesh).getConnectivity(elem);
auto node_iter = std::find(connectivity.begin(), connectivity.end(),
master_node);
if (node_iter != connectivity.end()) {
is_valid = false;
break;
}
}
Vector<Real> pos2(spatial_dimension);
for (UInt s : arange(spatial_dimension)) {
pos2(s) = this->positions(master_node, s);
}
Real distance = pos.distance(pos2);
if (distance <= closet_distance and is_valid) {
closet_master_node = master_node;
closet_distance = distance;
pair_exists = true;
}
}
}
if (pair_exists) {
contact_pairs.emplace_back(
std::make_pair(slave_node, closet_master_node));
}
}
}
}
/* -------------------------------------------------------------------------- */
void ContactDetector::createContactElements(
Array<ContactElement> & contact_elements, Array<Real> & gaps,
Array<Real> & normals, Array<Real> & tangents, Array<Real> & projections) {
auto surface_dimension = spatial_dimension - 1;
Real alpha;
switch (detection_type) {
case _explicit: {
alpha = 1.0;
break;
}
case _implicit: {
alpha = -1.0;
break;
}
default:
AKANTU_EXCEPTION(detection_type
<< " is not a valid contact detection type");
break;
}
for (auto & pairs : contact_pairs) {
const auto & slave_node = pairs.first;
Vector<Real> slave(spatial_dimension);
for (UInt s : arange(spatial_dimension)) {
slave(s) = this->positions(slave_node, s);
}
const auto & master_node = pairs.second;
Array<Element> elements;
this->mesh.getAssociatedElements(master_node, elements);
auto & gap = gaps.begin()[slave_node];
Vector<Real> normal(normals.begin(spatial_dimension)[slave_node]);
Vector<Real> projection(projections.begin(surface_dimension)[slave_node]);
Matrix<Real> tangent(
tangents.begin(surface_dimension, spatial_dimension)[slave_node]);
auto index = GeometryUtils::orthogonalProjection(
mesh, positions, slave, elements, gap, projection, normal, tangent,
alpha, this->max_iterations, this->projection_tolerance,
this->extension_tolerance);
// if a valid projection is not found on the patch of elements
// index is -1 or if not a valid self contact, the contact element
// is not created
if (index == UInt(-1) or !isValidSelfContact(slave_node, gap, normal)) {
gap *= 0;
normal *= 0;
projection *= 0;
tangent *= 0;
continue;
}
// create contact element
contact_elements.push_back(ContactElement(slave_node, elements[index]));
}
contact_pairs.clear();
}
} // namespace akantu

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