write matplotlib surfaceplot to stl file

[jkokorian]

Would it be possible to write a matplotlib trisurf plot to an stl file? (I was hoping to print my graphs on a 3d printer)

I've been messing around with the Poly3dCollection object that is returned by the trisurf command, but I do not understand how you can get the actual vectors out of it. I also do not completely understand what sort of data the Mesh constructor expects.

# %load http://matplotlib.org/mpl_examples/mplot3d/trisurf3d_demo2.py
import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.tri as mtri

# u, v are parameterisation variables
u = (np.linspace(0, 2.0 * np.pi, endpoint=True, num=50) * np.ones((10, 1))).flatten()
v = np.repeat(np.linspace(-0.5, 0.5, endpoint=True, num=10), repeats=50).flatten()

# This is the Mobius mapping, taking a u, v pair and returning an x, y, z
# triple
x = (1 + 0.5 * v * np.cos(u / 2.0)) * np.cos(u)
y = (1 + 0.5 * v * np.cos(u / 2.0)) * np.sin(u)
z = 0.5 * v * np.sin(u / 2.0)

# Triangulate parameter space to determine the triangles
tri = mtri.Triangulation(u, v)

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1, projection='3d')

# The triangles in parameter space determine which x, y, z points are
# connected by an edge
mobius_polycollection = ax.plot_trisurf(x, y, z, triangles=tri.triangles, cmap=plt.cm.Spectral)


# now convert mobius_polycollection to mesh
import stl

mobius_mesh = #I have no idea...

mobius_mesh.save('mobius.stl')

[jkokorian]

I'm hoping this is trivial for you, but if it's not, could you give me some pointers?

[wolph]

It took me a bit of experimenting as well, but this seems to do it:

from stl import mesh

data = np.zeros(len(tri.triangles), dtype=mesh.Mesh.dtype)
mobius_mesh = mesh.Mesh(data, remove_empty_areas=False)
mobius_mesh.x[:] = x[tri.triangles]
mobius_mesh.y[:] = y[tri.triangles]
mobius_mesh.z[:] = z[tri.triangles]
mobius_mesh.save('mobius.stl')

[wolph]

And the result of the rendered strip using the example from the README.rst

[jkokorian]

Can you do it purely based on what you get from the mobius_polycollection variable? In most cases one would just create a surface plot from some x,y,z data without explicitly defining the triangles. Sorry I didn't make that clear in the first place, I should have taken a simpler example.

[jkokorian]

Just to be completely clear: what I'm after is to be able to 3d-print any 3d surface plot that I make based on some x,y,z data. I'll come up with a better example soon.

[wolph]

The problem is that for STL files you need to have triangulated data, luckily Matplotlib has several solutions for that: http://matplotlib.org/api/tri_api.html

It seems that mobius_polycollection._vec might contain the needed data but Matplotlib appears to have very little useful documentation about these properties: http://matplotlib.org/mpl_toolkits/mplot3d/api.html?highlight=poly3dcollection#mpl_toolkits.mplot3d.art3d.Poly3DCollection
And I'm too strapped for time to look through the source right now.

[wolph]

Closing this since it's not really related to this library.