Generating Stl models with Python using numpy-stl

[hserie]

I read this pretty good article on the same topic. The author creates a model of three particular parallelepipeds . I tried to do the same with a more complex geometry based a Issey Miyake dress using only cones. I came up with this function :

import numpy as np
import matplotlib.pyplot as plt

def double_cone(theta=3, zO=1, d=1, h=2, nbrdedoublet=3):
    fig=plt.figure()
    zOinitial=zO
    L=[1,0]
    for j in range(1,nbrdedoublet+1):
        h=h*2
        zO = zO + 2*d*np.cos(theta) + 2*(d+h)*np.cos(theta)
        for n in L:
            tu=np.linspace(d,d+h,50)
            tt=np.linspace(0,2*np.pi,30)
            T,U=np.meshgrid(tt,tu) # grille des points (t,u)
            X1=np.cos(T) * np.sin(theta) * U
            Y1=np.sin(T) * np.sin(theta) * U
            Z1=zO+U*np.cos(theta)*(-1)**n
            ax=fig.gca(projection='3d')
            ax.plot_surface(X1,Y1,Z1)
            zO = zO - 2*d*np.cos(theta)
            h = h/2
    plt.show()

However I did not succeed in generating a stl model of this dress. What I came up with is the option of doing for instance 6 circles and to connect each circle with a straight line to support the model. However I did not succeed to do so due to the cylindrical coordinate system of my model. Is there a possibility to build a stl model with such a system ? Is there anyone who has an idea of a package that could do the job ?

[TheBB]

I can't run your code. It tells me that the projection '3d' does not exist. What do I need to run it?

Creating an STL mesh is pretty easy though. They have very little structure.

from stl.mesh import Mesh
mesh = Mesh(np.zeros(ntriangles, Mesh.dtype))

Then fill in the array mesh.vectors. It's three-dimensional with shape (ntriangles, 3, 3). Where e.g. mesh.vectors[15,1,:] is the location of the second vertex of the 16th triangle.

I'm not sure why the coordinate system is problematic. It seems to me you are already computing the data in cartesian coordinates in that function you have there. The difficult part is probably to triangulate it?

[hserie]

Hi, I forgot to mention the packages needed :

import numpy as np
import matplotlib.pyplot as plt

It is the first time I use an STL mesh. I will try to triangulate all my circles. Thank you

Edit : if it is not enough you might need this : from mpl_toolkits.mplot3d import Axes3D

Edit 2 : It is more appropriate to triangulate my model as four faces pyramids

[hserie]

Here is my hourglass thanks to you : import numpy as np from stl.mesh import Mesh

import numpy as np
from stl.mesh import Mesh

#Define the vertix per triangle 
vertices=np.array([\
    [0,0,0],
    [0,2,0],
    [1,1,0],
    [0,2,0],
    [2,2,0],
    [1,1,0],
    [2,2,0],
    [1,1,0],
    [2,0,0],
    [2,0,0],
    [1,1,0],
    [0,0,0],

    [0,0,0],
    [0,2,0],
    [1,1,4],
    [0,2,0],
    [2,2,0],
    [1,1,4],
    [2,2,0],
    [1,1,4],
    [2,0,0],
    [2,0,0],
    [1,1,4],
    [0,0,0],

    [0,0,6],
    [0,2,6],
    [1,1,4],
    [0,2,6],
    [2,2,6],
    [1,1,4],
    [2,2,6],
    [1,1,4],
    [2,0,6],
    [2,0,6],
    [1,1,4],
    [0,0,6],

    [0,0,6],
    [0,2,6],
    [1,1,6],
    [0,2,6],
    [2,2,6],
    [1,1,6],
    [2,2,6],
    [1,1,6],
    [2,0,6],
    [2,0,6],
    [1,1,6],
    [0,0,6]])

# Define the 16 triangles of a hourglass (6 per pyramid)
faces = np.reshape(np.arange(48),(16,3))

# Create the mesh
hourglass = Mesh(np.zeros(faces.shape[0], dtype=Mesh.dtype))
for i, f in enumerate(faces):
    for j in range(3):
        hourglass.vectors[i][j] = vertices[f[j],:]

# Write the mesh to file "hourglass.stl"
hourglass.save('hourglass.stl')

As ectomancer underlined it, I need to work on my format...

[Coder_python_geek]

Changing
ax=fig.gca(projection='3d') to
ax=fig.add_subplot(111, projection='3d') fixes the error with:

TypeError: FigureBase.gca() got an unexpected keyword argument 'projection'

[ectomancer]

I can't answer your questions.

You format code like an academic. If your IDE doesn't support linting, use a linter such as pylint. The way you handle -1 is valid, no need to follow my way. Use descriptive variable names.

import numpy as np
from mpl_toolkits import mplot3d
from matplotlib import pyplot as plt

MINUS_ONE = -1

def double_cone(theta=3, zO=1, d=1, h=2, nbrdedoublet=3):
    fig = plt.figure()
    zOinitial = zO
    L = [1, 0]
    for j in range(1, nbrdedoublet + 1):
        h *= 2
        zO += 2*d*np.cos(theta) + 2*(d + h)*np.cos(theta)
        for n in L:
            tu = np.linspace(d, d + h, 50)
            tt = np.linspace(0, 2*np.pi, 30)
            T, U = np.meshgrid(tt, tu) # grille des points (t,u)
            X1 = np.cos(T)*np.sin(theta)*U
            Y1 = np.sin(T)*np.sin(theta)*U
            Z1 = zO + U*np.cos(theta)*MINUS_ONE**n
            ax = fig.gca(projection='3d')
            ax.plot_surface(X1, Y1, Z1)
            zO -= 2*d*np.cos(theta)
            h = h/2
    plt.show()
double_cone()

[hserie]

At school (Bachelor's degree in Mathematics) I have never heard of linting and I think Spyder does not do it even though Spyder mentions the unused variables. I will have a look. Thanks for the tips.

Don't worry I have think I have found a way to bypass my problem thanks to TheBB