I was considering something like this:
x = linspace(-pi, pi, 20);
h = x(2)-x(1);
[X,Y] = ndgrid(x);
Z = sin(X) .* cos(Y);
[U,V] = gradient(Z,h,h);
W = zeros(size(U));
figure
surf(X, Y, Z)
hold on
quiver3(X,Y,Z, U,V,W, 0.7, 'r')
hold off
shading('interp')
grid on
view(0, 90)
All the arrows are visible because they all plot with respect to ‘Z’. The ‘W’ matrix simply makes them plot in a plane. (I made them red so they’re more visible.)
