53 lines
1.7 KiB
C++
53 lines
1.7 KiB
C++
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// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2014 Daniele Panozzo <daniele.panozzo@gmail.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#include "vector_area_matrix.h"
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#include "boundary_facets.h"
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#include <vector>
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// Bug in unsupported/Eigen/SparseExtra needs iostream first
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#include <iostream>
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#include <unsupported/Eigen/SparseExtra>
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template <typename DerivedF, typename Scalar>
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IGL_INLINE void igl::vector_area_matrix(
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const Eigen::PlainObjectBase<DerivedF> & F,
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Eigen::SparseMatrix<Scalar>& A)
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{
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using namespace Eigen;
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using namespace std;
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// number of vertices
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const int n = F.maxCoeff()+1;
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MatrixXi E;
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boundary_facets(F,E);
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//Prepare a vector of triplets to set the matrix
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vector<Triplet<Scalar> > tripletList;
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tripletList.reserve(4*E.rows());
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for(int k = 0; k < E.rows(); k++)
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{
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int i = E(k,0);
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int j = E(k,1);
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tripletList.push_back(Triplet<Scalar>(i+n, j, -0.25));
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tripletList.push_back(Triplet<Scalar>(j, i+n, -0.25));
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tripletList.push_back(Triplet<Scalar>(i, j+n, 0.25));
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tripletList.push_back(Triplet<Scalar>(j+n, i, 0.25));
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}
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//Set A from triplets (Eigen will sum triplets with same coordinates)
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A.resize(n * 2, n * 2);
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A.setFromTriplets(tripletList.begin(), tripletList.end());
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}
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#ifdef IGL_STATIC_LIBRARY
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// Explicit template instantiation
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template void igl::vector_area_matrix<Eigen::Matrix<int, -1, -1, 0, -1, -1>, double>(Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::SparseMatrix<double, 0, int>&);
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#endif
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