[FIXED] How to generate a 3D helix from a helical line?

Issue

I have x, y and z coordinates of a helical line like the blue line in the figure. The coordinates are 1D arrays. How can I convert this helical line to a helix surface like the one in the figure and plot it as a surface plot using matplotlib?

Helix surface plot

Solution

Assuming your helix is defined like

n = 100

z = np.linspace(0, 8*np.pi, n)
x = np.cos(z)
y = np.sin(z)

you can use plot_trisurf from matplotlib. First, you need to create outer and inner edge points. For example like this:

inner_radius = 0.6
outer_radius = 1.4

x_inner = np.cos(z)*inner_radius
x_outer = np.cos(z)*outer_radius
x_both = np.concatenate([x_inner, x_outer])

y_inner = np.sin(z)*inner_radius
y_outer = np.sin(z)*outer_radius
y_both = np.concatenate([y_inner, y_outer])

and then the triangles for triangulation

triangles = []
for i in range(0, n//2 - 1):
    triangles.append([i, i + 1, n + i])
    triangles.append([n + i + 1, n + i, i + 1])

And finally plot the surface

fig = plt.figure(figsize=(8, 8))
ax = plt.axes(projection='3d')
ax.plot_trisurf(x_both, y_both, np.concatenate([z, z]), triangles=triangles)
plt.show()

Result:

Answered By - maciek97x