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find_voro_cell.cc
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Wed, Jul 17, 17:06

find_voro_cell.cc
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// Example code demonstrating find_voronoi_cell function
//
// Author : Chris H. Rycroft (LBL / UC Berkeley)
// Email : chr@alum.mit.edu
// Date : August 30th 2011
#include "voro++.hh"
using namespace voro;
// The sampling distance for the grids of find_voronoi_cell calls
const double h=0.05;
// The cube of the sampling distance, corresponding the amount of volume
// associated with a sample point
const double hcube=h*h*h;
// Set the number of particles that are going to be randomly introduced
const int particles=20;
// This function returns a random double between 0 and 1
double rnd() {return double(rand())/RAND_MAX;}
int main() {
int i;
double x,y,z,r,rx,ry,rz;
// Create a container with the geometry given above, and make it
// non-periodic in each of the three coordinates. Allocate space for
// eight particles within each computational block
container con(0,1,0,1,0,1,5,5,5,false,false,false,8);
// Randomly add particles into the container
for(i=0;i<particles;i++) {
x=rnd();
y=rnd();
z=rnd();
con.put(i,x,y,z);
}
// Output the particle positions in gnuplot format
con.draw_particles("find_voro_cell_p.gnu");
// Scan a 2D slice in the container, and for each point in the slice,
// find the Voronoi cell that the point is in. Store a vector
FILE *f1=safe_fopen("find_voro_cell.vec","w");
for(x=0.5*h;x<1;x+=h) for(y=0.5*h;y<1;y+=h) {
if(con.find_voronoi_cell(x,y,0.5,rx,ry,rz,i))
fprintf(f1,"%g %g %g %g %g %g %g\n",x,y,0.5,rx-x,ry-y,rz-0.5,
sqrt((rx-x)*(rx-x)+(ry-y)*(ry-y)+(rz-0.5)*(rz-0.5)));
else fprintf(stderr,"# find_voronoi_cell error for %g %g 0.5\n",x,y);
}
fclose(f1);
// Create a blank array for storing the sampled Voronoi volumes
int samp_v[particles];
for(i=0;i<particles;i++) samp_v[i]=0;
// Scan over a grid covering the entire container, finding which
// Voronoi cell each point is in, and tallying the result as a method
// of sampling the volume of each Voronoi cell
for(z=0.5*h;z<1;z+=h) for(y=0.5*h;y<1;y+=h) for(x=0.5*h;x<1;x+=h) {
if(con.find_voronoi_cell(x,y,z,rx,ry,rz,i)) samp_v[i]++;
else fprintf(stderr,"# find_voronoi_cell error for %g %g %g\n",x,y,z);
}
// Output the Voronoi cells in gnuplot format and a file with the
// comparisons between the Voronoi cell volumes and the sampled volumes
f1=safe_fopen("find_voro_cell.vol","w");
FILE *f2=safe_fopen("find_voro_cell_v.gnu","w");
c_loop_all cla(con);
voronoicell c;
if(cla.start()) do if (con.compute_cell(c,cla)) {
// Get the position and ID information for the particle
// currently being considered by the loop. Ignore the radius
// information.
cla.pos(i,x,y,z,r);
// Save and entry to the .vol file, storing both the computed
// Voronoi cell volume, and the sampled volume based on the
// number of grid points that were inside the cell
fprintf(f1,"%d %g %g %g %g %g\n",i,x,y,z,c.volume(),samp_v[i]*hcube);
// Draw the Voronoi cell
c.draw_gnuplot(x,y,z,f2);
} while (cla.inc());
fclose(f1);
fclose(f2);
}

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