
[Y,X,Z] = ndgrid(linspace(-2,2,15),linspace(-2,2,15),linspace(-2,2,15));
V = X.^2+Y.^2-Z.^2; %k=f(x,y,z) level surface
p = patch(isosurface(X,Y,Z,V,-1)); %last entry sets V=val
isonormals(X,Y,Z,V,p);
set(p,'FaceColor','y','EdgeColor','k','FaceAlpha',0.5); % ou
'EdgeColor','none'
daspect([1 1 1])
axis square;
grid on;
camlight
view(-27,20);
lighting gouraud;