I tried to summarize the operations that are likely to be used with numpy-stl

Introduction

I thought it would be easy if the things to be modeled with a 3D printer became a pattern and I could create a model without permission by entering numbers, but I found out what is called numpy-stl, so I summarized it as a memo.

What is numpy-stl?

A rough translation of the official document looks like this.

A simple library for working with STL files (as well as common 3D models) quickly and easily. All operations rely heavily on numpy and are one of the fastest STL libraries for Python.

In short, it's a library where you can create 3D models like numpy and play with existing STL files.

Official website and reference materials

--numpy-stl project page https://pypi.org/project/numpy-stl/ --numpy-stl documentation https://numpy-stl.readthedocs.io/en/latest/ --3D printing x Python ~ 3D printing approaching from code ~ https://www.slideshare.net/TakuroWada/3dpython3d

Installation

Basically, pip is OK. This time, I ran it on macOS Catalina 10.15.6, python 3.7.7.

install

pip3 install numpy-stl

If you want to check the generated 3D model, also install the following libraries.

install

pip3 install mpl_toolkits
pip3 install matplotlib

Various operations

I will add it when I feel like rotating. (However, if you google with numpy-stl, you will see quite a few articles like that.)

I want to make a cube (regular hexahedron)

I made it a function because it was a big deal. Enter the size in the arguments scale_x, scale_y, scale_z. Depending on the unit system, you should be able to create a cube with a height and width of 1 in the default state with no arguments.

cube_model.py

import numpy as np
from stl import mesh

def cube_model(scaleX=1, scaleY=1, scaleZ=1):
    scaleX = scaleX / 2
    scaleY = scaleY / 2
    scaleZ = scaleZ / 2

    vertices = np.array([\
        [-1*scaleX, -1*scaleY, -1*scaleZ],
        [+1*scaleX, -1*scaleY, -1*scaleZ],
        [+1*scaleX, +1*scaleY, -1*scaleZ],
        [-1*scaleX, +1*scaleY, -1*scaleZ],
        [-1*scaleX, -1*scaleY, +1*scaleZ],
        [+1*scaleX, -1*scaleY, +1*scaleZ],
        [+1*scaleX, +1*scaleY, +1*scaleZ],
        [-1*scaleX, +1*scaleY, +1*scaleZ]])

    faces = np.array([\
        [0,3,1],
        [1,3,2],
        [0,4,7],
        [0,7,3],
        [4,5,6],
        [4,6,7],
        [5,1,2],
        [5,2,6],
        [2,3,6],
        [3,7,6],
        [0,1,5],
        [0,5,4]])

    cube = mesh.Mesh(np.zeros(faces.shape[0], dtype=mesh.Mesh.dtype))
    cube.remove_duplicate_polygons=True
    for i, f in enumerate(faces):
        for j in range(3):
            cube.vectors[i][j] = vertices[f[j],:]

    return cube

Click here for the program to load

test_plot.py

import numpy as np
from stl import mesh
from mpl_toolkits import mplot3d
from matplotlib import pyplot
from cube_model import cube_model

figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

your_mesh = cube_model(10,10,10)
axes.add_collection3d(mplot3d.art3d.Poly3DCollection(your_mesh.vectors))

scale = your_mesh.points.flatten()
print(scale)
axes.auto_scale_xyz(scale, scale, scale)

pyplot.show()

I want to load my STL

Specify your own STL file in your_stl_model.stl.

read_stl_file.py

import numpy as np
from stl import mesh
from mpl_toolkits import mplot3d
from matplotlib import pyplot

figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

your_mesh = mesh.Mesh.from_file('your_stl_model.stl')
axes.add_collection3d(mplot3d.art3d.Poly3DCollection(your_mesh.vectors))

scale = cube_comb.points.flatten()
axes.auto_scale_xyz(scale, scale, scale)

pyplot.show()

I want to align the 3D model with the origin

It is used to align the center of the model with (0,0,0) when the read STL is flying in a strange direction. In the argument my_mesh, put the mesh object when the STL file etc. is read.

mesh_location_zero.py

import numpy as np
from stl import mesh

def mesh_location_zero(my_mesh):
    midPosRel = (my_mesh.max_ - my_mesh.min_)/2
    my_mesh.x = my_mesh.x - (midPosRel[0] + my_mesh.min_[0])
    my_mesh.y = my_mesh.y - (midPosRel[1] + my_mesh.min_[1])
    my_mesh.z = my_mesh.z - (midPosRel[2] + my_mesh.min_[2])
    return my_mesh

Update mesh information

In order to update the members in the mesh object, this is also executed when moving, including adjusting the coordinate system, or expanding, rotating, or changing the model. The arguments are the same.

mesh_update.py

import numpy as np
from stl import mesh

def mesh_update(my_mesh):
    my_mesh.update_areas()
    my_mesh.update_max()
    my_mesh.update_min()
    my_mesh.update_units()
    return my_mesh

I want to scale the 3D model

Enlargement / reduction has also been made into a function. Put your own 3D model in my_mesh, and put 1.0 as 100% in scale_x, scale_y, and scale_z.

mesh_scale.py

import numpy as np
from stl import mesh

def mesh_scale(my_mesh, scale_x, scale_y, scale_z):
    my_mesh.x = my_mesh.x * scale_x
    my_mesh.y = my_mesh.y * scale_y
    my_mesh.z = my_mesh.z * scale_z 
    return my_mesh

I want to move a 3D model

You can move it with mesh.translate. Arguments are specified in numpy.array. (This time, I also use cube_model.py.)

move_model.py

import numpy as np
from stl import mesh
from mpl_toolkits import mplot3d
from matplotlib import pyplot
from cube_model import cube_model

figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

your_mesh = cube_model(5,20,5)
your_mesh.translate(np.array([1,3,1]))

axes.add_collection3d(mplot3d.art3d.Poly3DCollection(your_mesh.vectors))

scale = cube_comb.points.flatten()
print(scale)
axes.auto_scale_xyz(scale, scale, scale)

pyplot.show()

I want to combine 3D models

You can combine models with numpy.concatenate. I'm just selling that I can make a model with numpy. (This time, I also use cube_model.py.)

mesh_scale.py

import numpy as np
from stl import mesh
from mpl_toolkits import mplot3d
from matplotlib import pyplot
from cube_model import cube_model

figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

your_mesh = cube_model(10,10,10)
your_mesh2 = cube_model(5,20,5)
your_mesh2.translate(np.array([1,1,1]))

cube_comb = mesh.Mesh(np.concatenate([
    your_mesh.data.copy(),
    your_mesh2.data.copy(),
]))

axes.add_collection3d(mplot3d.art3d.Poly3DCollection(cube_comb.vectors))

scale = cube_comb.points.flatten()
print(scale)
axes.auto_scale_xyz(scale, scale, scale)

pyplot.show()

I want to save a 3D model

Can be saved with mesh.save. The arguments are the save destination path and file name.

save_model.py

import numpy as np
from stl import mesh
from cube_model import cube_model

your_mesh = cube_model(10,10,10)
your_mesh2 = cube_model(5,20,5)
your_mesh2.translate(np.array([1,1,1]))

cube_comb = mesh.Mesh(np.concatenate([
    your_mesh.data.copy(),
    your_mesh2.data.copy(),
]))

cube_comb.save('your_model.stl')

bonus

I tried to stream the STL data created in the software "XYZprint" used to stream the modeling data with a 3D printer made by XYZprinting. I'm glad that the stacked data can be created properly.

in conclusion

This time I tried to operate numpy-stl. If there are other operations that you might use in general, add them when you feel like it.