[x, y, z] = meshgrid (-2:2:0, -1:0.25:1, -1:0.25:1);
u = ones (size (x));
v = zeros (size (x));
w = zeros (size (x));
ostreamtube (x, y, z, u, v, w, -2, 0, 0, [5, 60]);
hold on;
quiver3 (x, y, z, u, v, w);
view (3);
grid on;
axis tight equal;
title ("should start at -2");