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torus.cc
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// Custom wall class example code
//
// Author : Chris H. Rycroft (LBL / UC Berkeley)
// Email : chr@alum.mit.edu
// Date : August 30th 2011
#include "voro++.hh"
using namespace voro;
// Major and minor torus radii
const double arad=9,brad=3.5;
// The outer radius of the torus, that determines how big the container should
// be
const double crad=arad+brad;
// Set up constants for the container geometry
const double x_min=-crad-0.5,x_max=crad+0.5;
const double y_min=-crad-0.5,y_max=crad+0.5;
const double z_min=-brad-0.5,z_max=brad+0.5;
// Set the computational grid size
const int n_x=10,n_y=10,n_z=3;
// This class creates a custom toroidal wall object that is centered on the
// origin and is aligned with the xy plane. It is derived from the pure virtual
// "wall" class. The "wall" class contains virtual functions for cutting the
// Voronoi cell in response to a wall, and for telling whether a given point is
// inside the wall or not. In this derived class, specific implementations of
// these functions are given.
class wall_torus : public wall {
public:
// The wall constructor initializes constants for the major and
// minor axes of the torus. It also initializes the wall ID
// number that is used when the plane cuts are made. This is
// only tracked with the voronoicell_neighbor class and is
// ignored otherwise. It can be omitted, and then an arbitrary
// value of -99 is used.
wall_torus(double imjr,double imnr,int iw_id=-99)
: w_id(iw_id), mjr(imjr), mnr(imnr) {};
// This returns true if a given vector is inside the torus, and
// false if it is outside. For the current example, this
// routine is not needed, but in general it would be, for use
// with the point_inside() routine in the container class.
bool point_inside(double x,double y,double z) {
double temp=sqrt(x*x+y*y)-mjr;
return temp*temp+z*z<mnr*mnr;
}
// This template takes a reference to a voronoicell or
// voronoicell_neighbor object for a particle at a vector
// (x,y,z), and makes a plane cut to to the object to account
// for the toroidal wall
template<class vc_class>
inline bool cut_cell_base(vc_class &c,double x,double y,double z) {
double orad=sqrt(x*x+y*y);
double odis=orad-mjr;
double ot=odis*odis+z*z;
// Unless the particle is within 1% of the major
// radius, then a plane cut is made
if(ot>0.01*mnr) {
ot=2*mnr/sqrt(ot)-2;
z*=ot;
odis*=ot/orad;
x*=odis;
y*=odis;
return c.nplane(x,y,z,w_id);
}
return true;
}
// These virtual functions are called during the cell
// computation in the container class. They call instances of
// the template given above.
bool cut_cell(voronoicell &c,double x,
double y,double z) {return cut_cell_base(c,x,y,z);}
bool cut_cell(voronoicell_neighbor &c,double x,
double y,double z) {return cut_cell_base(c,x,y,z);}
private:
// The ID number associated with the wall
const int w_id;
// The major radius of the torus
const double mjr;
// The minor radius of the torus
const double mnr;
};
int main() {
// 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(x_min,x_max,y_min,y_max,z_min,z_max,n_x,n_y,n_z,
false,false,false,8);
// Add the custom toroidal wall to the container
wall_torus tor(arad,brad);
con.add_wall(tor);
// Import the particles from a file
con.import("pack_torus");
// Output the particle positions in POV-Ray format
con.draw_particles_pov("torus_p.pov");
// Output the Voronoi cells in POV-Ray format
con.draw_cells_pov("torus_v.pov");
}

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