14d

Hi all,

Using the below code, simply I can draw a surface that I need.

```
import plotly.figure_factory as ff
import numpy as np
from scipy.spatial import Delaunay
u = np.linspace(0, np.pi, 24)
v = np.linspace(-1, 0, 8)
u,v = np.meshgrid(u,v)
u = u.flatten()
v = v.flatten()
z = np.sin(u/2)#*0+1
points2D = np.vstack([u,v]).T
tri = Delaunay(points2D)
simplices = tri.simplices
fig = ff.create_trisurf(x=u, y=v, z=z,
colormap="Portland",
simplices=simplices,
title="Mobius Band")
fig.show()
```

and the result is correct as I need:

But when I make the surface horizontal, I encounter with error?

```
import plotly.figure_factory as ff
import numpy as np
from scipy.spatial import Delaunay
u = np.linspace(0, np.pi, 24)
v = np.linspace(-1, 0, 8)
u,v = np.meshgrid(u,v)
u = u.flatten()
v = v.flatten()
z = np.sin(u/2)*0+1
points2D = np.vstack([u,v]).T
tri = Delaunay(points2D)
simplices = tri.simplices
fig = ff.create_trisurf(x=u, y=v, z=z,
colormap="Portland",
simplices=simplices,
title="Mobius Band")
fig.show()
```

What is the problem???