function [x,y,z] = get_points(filename)
% read set of points from a file (each line x,y,z coordinates)
% and return the results in 3 arrays x,y, and z
%
 
fid = fopen(filename);
crd = fscanf(fid,'%f');
dim = length(crd);
x = crd(1:3:dim-2);
y = crd(2:3:dim-1);
z = crd(3:3:dim);