Quiver plot arrows hidden by surface plot?

Hello all,

I am creating a surface plot, and plotting on top of this a quiver plot. Everything works great, however where I have large "z" values on my surface plot, the quiver arrows are being hidden by the graph.

Any ideas how to solve this? I have attached an image of my problem, look at the yellow boxes, where the quiver arrows are hidden.

Answer 1

[Star Strider]

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.)

[Mark Lepage]

Thank you very much, this has effectively solved my problem, and produced a much nicer graph.

Could you please explain a little more how to implement the z-offset on the quiver plot.

I believe 100% that this is the problem.

I appreciate your help a lot.

[Star Strider]

My pleasure.

The Z-offset is simply the zeros ‘W’ matrix that effectively plots the arrows on top of the surf plot. Instead of 3D quiver arrows, the ‘W’ matrix creates the arrows as a 2D plane, however with their origins on the ‘Z’ values of the surf plot. You can see this by using the GUI (‘Tools’ -> ‘Rotate 3D’) or the view function to rotate the plot to see the arrows with respect to the ‘Z’ surface elevation. They all plot above it, regardless of where they originate.

That’s probably as well as I can explain it.

Answer 2

[Thomas Rosin]

I don't think there are hidden, I just think your arrow size is too small.

The tip of the arrow scale with its length but it's a parameters you can set on the quiver function.

[Mark Lepage]

Thanks for your answer Thomas,

When I simply rotate the graph (for display purposes I don't want to do this), the quivers become visible.

[Star Strider]

If you don’t need the gridlines on your surf plot, you can set ‘EdgeColor’ (link) to be 'none' or 'interp', and you can set shading (link) to interp as well.

Either of those would likely make the arrows more visible.

[Mark Lepage]

Thanks for the answer, this does look much better and easier to visualize.

However, the middle arrows are still missing! Any ideas for this?

[Star Strider]

My pleasure.

‘However, the middle arrows are still missing! Any ideas for this?’

Not really. I have no idea what you’re doing.

So I’m guessing here. One possibility is to plot the surf plot first, and the quiver plot afterwards. Another might be to add a ‘z’ coordinate to the quiver plot (perhaps the ‘z’ values of the surf plot, or plot the arrows on a plane higher than the maximum ‘z’ value of the surf plot) so that the arrows plot above the surf plot.

[Mark Lepage]

Just wanted to show you the improvement in my chart.

Much appreciated.

[Star Strider]

@Mark Lepage —

As always, my pleasure.