53 lines
1.5 KiB
C++
53 lines
1.5 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) 2013 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_dir.h"
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#include <igl/PI.h>
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#include <cmath>
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IGL_INLINE Eigen::Vector3d igl::random_dir()
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{
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using namespace Eigen;
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double z = (double)rand() / (double)RAND_MAX*2.0 - 1.0;
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double t = (double)rand() / (double)RAND_MAX*2.0*PI;
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// http://www.altdevblogaday.com/2012/05/03/generating-uniformly-distributed-points-on-sphere/
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double r = sqrt(1.0-z*z);
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double x = r * cos(t);
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double y = r * sin(t);
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return Vector3d(x,y,z);
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}
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IGL_INLINE Eigen::MatrixXd igl::random_dir_stratified(const int n)
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{
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using namespace Eigen;
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using namespace std;
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const double m = std::floor(sqrt(double(n)));
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MatrixXd N(n,3);
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int row = 0;
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for(int i = 0;i<m;i++)
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{
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const double x = double(i)*1./m;
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for(int j = 0;j<m;j++)
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{
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const double y = double(j)*1./m;
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double z = (x+(1./m)*(double)rand() / (double)RAND_MAX)*2.0 - 1.0;
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double t = (y+(1./m)*(double)rand() / (double)RAND_MAX)*2.0*PI;
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double r = sqrt(1.0-z*z);
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N(row,0) = r * cos(t);
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N(row,1) = r * sin(t);
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N(row,2) = z;
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row++;
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}
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}
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// Finish off with uniform random directions
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for(;row<n;row++)
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{
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N.row(row) = random_dir();
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}
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return N;
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}
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