Mask_points doesn't work for mesh

I'm using mesh() to plot a surface defined by 2D arrays of 20 points and I would like to reduce the displayed points, I saw the mask_points kwarg would do just what I want, but for some reason it isn't working. I tried an example with quiver3d() and it works fine.

This is the code, for any value on mask_points, the plot remains the same.

```
import numpy as np
from mayavi import mlab

k = 2*np.pi
long = 0.5
numberpts=20
theta = np.linspace(0, np.pi, numberpts)
phi = np.linspace(0, 2*np.pi, numberpts)
PHI, THETA = np.meshgrid(phi, theta)
R = np.absolute((np.cos(k*long/2*np.cos(THETA))-np.cos(k*long/2))/np.sin(THETA))
R = np.nan_to_num(R)
X = R * np.sin(THETA) * np.cos(PHI)
Y = R * np.sin(THETA) * np.sin(PHI)
Z = R * np.cos(THETA)
plot = mlab.mesh(X, Y, Z, mask_points =2)
mlab.show()
```