```
% create a set of electrodes, randomly placed on a sphere
elec = [];
elec.pnt = randn(128,3);
radius = sqrt(sum(elec.pnt.^2,2));
elec.pnt = elec.pnt ./ [radius radius radius]; % scale them to a unit sphere
for i=1:128
elec.label{i} = sprintf('%03d', i);
end
elec.elecpos = elec.pnt;
% create a concentric 3-sphere volume conductor, the radius is the same as for the electrodes
vol = [];
vol.r = [0.88 0.92 1.00]; % radii of spheres
vol.c = [1 1/80 1]; % conductivity
vol.o = [0 0 0]; % center of sphere
% compute the leadfield for a dipole at position [0 0 0.5]
pos = [0 0 0.5];
lf = ft_compute_leadfield(pos, elec, vol);
% compute the potential distribution for a dipole with x-orientation
mom = [1 0 0]';
pot = lf * mom;
% plot the 3-D distribution of the potential over the sphere surface
elec.tri = convhulln(elec.pnt)
figure
patch('faces', elec.tri, 'vertices', elec.pnt, 'FaceVertexCData', pot, 'FaceColor', 'interp')
axis equal; axis vis3d
```