xstar);
sf  = sqrt(vf);

%% Visualise GP Outputs

% Build a colormap
cmap = jet(5); 
levels = linspace(-2.5,3.5,5);

% Generate isosurfaces
figure; 
for ii = 1:5
    camlight
    lighting gouraud
    hh(ii) = patch(isosurface(xeva, yeva, zeva, reshape(mf,size(xeva)), levels(ii)));
    set(hh(ii), 'Facecolor', cmap(ii,:), 'Edgecolor', 'none', 'facealpha', (1-(5-abs(levels(ii)))/5));
    axis([-3 3 -3 3 -3 3])
    caxis([-4,5]);
    xlabel('x');ylabel('y');zlabel('z')
    colorbar
end
 title('Predictive Mean'