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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.org). *
* *
* This program is free software; you can redistribute it and/or *
* modify it under the terms of the GNU General Public License as *
* published by the Free Software Foundation; either version 2 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* This program 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 *
* General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program. If not, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include "triangulation/dim2.h"
#include "triangulation/dim3.h"
#include <sstream>
namespace regina {
Vertex<3>::~Face() {
delete linkTri_;
}
const Triangulation<2>& Face<3, 0>::buildLink() const {
if (! linkTri_) {
// Build the triangulation.
auto* ans = new Triangulation<2>();
ans->newTriangles(degree());
size_t i = 0;
for (auto it = begin(); it != end(); ++it, ++i) {
Tetrahedron<3>* tet = it->tetrahedron();
int v = it->vertex();
for (int exitTri = 0; exitTri < 4; ++exitTri) {
if (exitTri == v)
continue;
Tetrahedron<3>* adj = tet->adjacentTetrahedron(exitTri);
if (! adj)
continue;
int edgeInLink = tet->triangleMapping(v).pre(exitTri);
if (ans->triangle(i)->adjacentTriangle(edgeInLink)) {
// We've already made this gluing in the vertex link
// from the other side.
continue;
}
int adjVertex = tet->adjacentGluing(exitTri)[v];
// TODO: We need to find which *embedding* corresponds to
// the adjacent tetrahedron/vertex pair.
// Currently we do a simple linear scan, which makes the
// overall link construction quadratic. This can surely be
// made linear(ish) with the right data structure / algorithm.
size_t adjIndex = 0;
for (auto adjIt = begin(); adjIt != end(); ++adjIt, ++adjIndex)
if (adjIt->tetrahedron() == adj &&
adjIt->vertex() == adjVertex)
break; // Sets adjIndex to the right value.
ans->triangle(i)->join(edgeInLink, ans->triangle(adjIndex),
Perm<3>::contract(adj->triangleMapping(adjVertex).inverse() *
tet->adjacentGluing(exitTri) *
tet->triangleMapping(v)));
}
}
// This is a construct-on-demand member: cast away constness to
// set it here.
const_cast<Vertex<3>*>(this)->linkTri_ = ans;
}
return *linkTri_;
}
Isomorphism<3> Face<3, 0>::buildLinkInclusion() const {
Isomorphism<3> inclusion(degree());
size_t i = 0;
for (auto it = begin(); it != end(); ++it, ++i) {
inclusion.tetImage(i) = it->tetrahedron()->index();
inclusion.facetPerm(i) = it->tetrahedron()->triangleMapping(
it->vertex());
}
return inclusion;
}
} // namespace regina
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