ndt histogram_direction

N_FLAT_BINS=40;
dlong = pi*(3-sqrt(5.0));  % ~2.39996323
dz    = 2.0/N_FLAT_BINS;
longitude = 0;
z    = 1 - dz/2;
directions=zeros(3,N_FLAT_BINS);
for  k = 1:N_FLAT_BINS
    r = sqrt(1-z*z);
    v=[1*cos(longitude)*r 1*sin(longitude)*r z]‘;
    directions(:,k)=v;
    z = z - dz;
    longitude = longitude + dlong;
end

figure(1)
plot3(directions(1,:),directions(2,:),directions(3,:),‘r.‘,0,0,0,‘b.‘), hold on, axis equal
for  k = 1:N_FLAT_BINS-1
    plot3([directions(1,k) 0],[directions(2,k) 0],[directions(3,k) 0],‘y-‘,‘LineWidth‘,1);
    plot3([directions(1,k) directions(1,k+1)],[directions(2,k) directions(2,k+1)],[directions(3,k) directions(3,k+1)],‘LineWidth‘,1);
end