84 lines
3.3 KiB
C++
84 lines
3.3 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 Alec Jacobson <alecjacobson@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 "random_points_on_mesh.h"
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#include "doublearea.h"
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#include "cumsum.h"
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#include "histc.h"
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#include <iostream>
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#include <cassert>
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template <typename DerivedV, typename DerivedF, typename DerivedB, typename DerivedFI>
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IGL_INLINE void igl::random_points_on_mesh(
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const int n,
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const Eigen::PlainObjectBase<DerivedV > & V,
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const Eigen::PlainObjectBase<DerivedF > & F,
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Eigen::PlainObjectBase<DerivedB > & B,
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Eigen::PlainObjectBase<DerivedFI > & FI)
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{
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using namespace Eigen;
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using namespace std;
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typedef typename DerivedV::Scalar Scalar;
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typedef Matrix<Scalar,Dynamic,1> VectorXs;
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VectorXs A;
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doublearea(V,F,A);
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A /= A.array().sum();
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// Should be traingle mesh. Although Turk's method 1 generalizes...
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assert(F.cols() == 3);
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VectorXs C;
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VectorXs A0(A.size()+1);
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A0(0) = 0;
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A0.bottomRightCorner(A.size(),1) = A;
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// Even faster would be to use the "Alias Table Method"
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cumsum(A0,1,C);
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const VectorXs R = (VectorXs::Random(n,1).array() + 1.)/2.;
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assert(R.minCoeff() >= 0);
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assert(R.maxCoeff() <= 1);
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histc(R,C,FI);
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const VectorXs S = (VectorXs::Random(n,1).array() + 1.)/2.;
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const VectorXs T = (VectorXs::Random(n,1).array() + 1.)/2.;
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B.resize(n,3);
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B.col(0) = 1.-T.array().sqrt();
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B.col(1) = (1.-S.array()) * T.array().sqrt();
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B.col(2) = S.array() * T.array().sqrt();
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}
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template <typename DerivedV, typename DerivedF, typename ScalarB, typename DerivedFI>
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IGL_INLINE void igl::random_points_on_mesh(
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const int n,
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const Eigen::PlainObjectBase<DerivedV > & V,
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const Eigen::PlainObjectBase<DerivedF > & F,
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Eigen::SparseMatrix<ScalarB > & B,
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Eigen::PlainObjectBase<DerivedFI > & FI)
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{
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using namespace Eigen;
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using namespace std;
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Matrix<ScalarB,Dynamic,3> BC;
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random_points_on_mesh(n,V,F,BC,FI);
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vector<Triplet<ScalarB> > BIJV;
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BIJV.reserve(n*3);
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for(int s = 0;s<n;s++)
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{
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for(int c = 0;c<3;c++)
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{
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assert(FI(s) < F.rows());
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assert(FI(s) >= 0);
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const int v = F(FI(s),c);
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BIJV.push_back(Triplet<ScalarB>(s,v,BC(s,c)));
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}
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}
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B.resize(n,V.rows());
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B.reserve(n*3);
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B.setFromTriplets(BIJV.begin(),BIJV.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::random_points_on_mesh<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, double, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(int, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::SparseMatrix<double, 0, int>&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> >&);
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template void igl::random_points_on_mesh<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, double, Eigen::Matrix<int, -1, 1, 0, -1, 1> >(int, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&, Eigen::SparseMatrix<double, 0, int>&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> >&);
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#endif
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