odd_even.cc
706c4ccdaefdefficient_neuronet

odd_even.cc
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			// Odd/even face coloring code
			//
			// Author : Chris H. Rycroft (LBL / UC Berkeley)
			// Email : chr@alum.mit.edu
			// Date : August 30th 2011

			#include <vector>
			using namespace std;

			#include "voro++.hh"
			using namespace voro;

			// This function returns a random floating point number between 0 and 1
			double rnd() {return double(rand())/RAND_MAX;}

			int main() {
			unsigned int i;
			double x,y,z,rsq,r;
			voronoicell v;

			// Initialize the Voronoi cell to be a cube of side length 2, centered
			// on the origin
			v.init(-1,1,-1,1,-1,1);

			// Cut the cell by 250 random planes which are all a distance 1 away
			// from the origin, to make an approximation to a sphere
			for(i=0;i<250;i++) {
			x=2*rnd()-1;
			y=2*rnd()-1;
			z=2*rnd()-1;
			rsq=xx+yy+z*z;
			if(rsq>0.01&&rsq<1) {
			r=1/sqrt(rsq);x=r;y=r;z*=r;
			v.plane(x,y,z,1);
			}
			}

			// Calculate the orders of the faces and the normal vectors
			vector<int> f_vert;
			vector<double> nor;
			v.face_orders(f_vert);
			v.normals(nor);

			// Output POV-Ray planes with textures based on whether a face is
			// composed of an odd or even number of edges
			const char* parity[2]={"even","odd"};
			FILE *fp=safe_fopen("odd_even_pl.pov","w");
			for(i=0;i<f_vert.size();i++)
			fprintf(fp,"plane{<%g,%g,%g>,0.5 texture{t_%s}}\n"
			,nor[3i],nor[3i+1],nor[3*i+2]
			,parity[f_vert[i]&1]);
			fclose(fp);

			// Save the Voronoi cell as a spheres and cylinders
			v.draw_pov(0,0,0,"odd_even_v.pov");
			}