60 lines
1.7 KiB
C++
60 lines
1.7 KiB
C++
// 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 "partition.h"
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#include "mat_min.h"
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IGL_INLINE void igl::partition(
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const Eigen::MatrixXd & W,
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const int k,
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Eigen::Matrix<int,Eigen::Dynamic,1> & G,
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Eigen::Matrix<int,Eigen::Dynamic,1> & S,
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Eigen::Matrix<double,Eigen::Dynamic,1> & D)
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{
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// number of mesh vertices
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int n = W.rows();
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// Resize output
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G.resize(n);
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S.resize(k);
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// "Randomly" choose first seed
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// Pick a vertex farthest from 0
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int s;
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(W.array().square().matrix()).rowwise().sum().maxCoeff(&s);
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S(0) = s;
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// Initialize distance to closest seed
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D = ((W.rowwise() - W.row(s)).array().square()).matrix().rowwise().sum();
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G.setZero();
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// greedily choose the remaining k-1 seeds
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for(int i = 1;i<k;i++)
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{
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// Find maximum in D
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D.maxCoeff(&s);
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S(i) = s;
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// distance to this seed
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Eigen::Matrix<double,Eigen::Dynamic,1> Ds =
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((W.rowwise() - W.row(s)).array().square()).matrix().rowwise().sum();
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// Concatenation of D and Ds: DDs = [D Ds];
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Eigen::Matrix<double,Eigen::Dynamic,Eigen::Dynamic> DDs;
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// Make space for two columns
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DDs.resize(D.rows(),2);
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DDs.col(0) = D;
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DDs.col(1) = Ds;
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// Update D
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// get minimum of old D and distance to this seed, C == 1 if new distance
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// was smaller
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Eigen::Matrix<int,Eigen::Dynamic,1> C;
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igl::mat_min(DDs,2,D,C);
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G = (C.array() ==0).select(G,i);
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}
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}
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