text: // Odd/even face coloring code
  //
  // Author   : Chris H. Rycroft (LBL / UC Berkeley)
  // Email    : chr@alum.mit.edu
  // Date     : August 30th 2011
  
  #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=x*x+y*y+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[3*i],nor[3*i+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");
  }
  