numpy-stl

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Simple library to make working with STL files (and 3D objects in general) fast and easy.

Due to all operations heavily relying on numpy this is one of the fastest STL editing libraries for Python available.

Links

• The source: https://github.com/WoLpH/numpy-stl
• Project page: https://pypi.python.org/pypi/numpy-stl
• Reporting bugs: https://github.com/WoLpH/numpy-stl/issues
• Documentation: http://numpy-stl.readthedocs.org/en/latest/
• My blog: https://wol.ph/

Requirements for installing:

• numpy_ any recent version
• python-utils_ version 1.6 or greater

Installation:

pip install numpy-stl

Initial usage:

• stl2bin your_ascii_stl_file.stl new_binary_stl_file.stl
• stl2ascii your_binary_stl_file.stl new_ascii_stl_file.stl
• stl your_ascii_stl_file.stl new_binary_stl_file.stl

Contributing:

Contributions are always welcome. Please view the guidelines to get started: https://github.com/WoLpH/numpy-stl/blob/develop/CONTRIBUTING.rst

Quickstart

.. code-block:: python

import numpy
from stl import mesh

# Using an existing stl file:
your_mesh = mesh.Mesh.from_file('some_file.stl')

# Or creating a new mesh (make sure not to overwrite the `mesh` import by
# naming it `mesh`):
VERTICE_COUNT = 100
data = numpy.zeros(VERTICE_COUNT, dtype=mesh.Mesh.dtype)
your_mesh = mesh.Mesh(data, remove_empty_areas=False)

# The mesh normals (calculated automatically)
your_mesh.normals
# The mesh vectors
your_mesh.v0, your_mesh.v1, your_mesh.v2
# Accessing individual points (concatenation of v0, v1 and v2 in triplets)
assert (your_mesh.points[0][0:3] == your_mesh.v0[0]).all()
assert (your_mesh.points[0][3:6] == your_mesh.v1[0]).all()
assert (your_mesh.points[0][6:9] == your_mesh.v2[0]).all()
assert (your_mesh.points[1][0:3] == your_mesh.v0[1]).all()

your_mesh.save('new_stl_file.stl')

Plotting using matplotlib_ is equally easy:

.. code-block:: python

from stl import mesh
from mpl_toolkits import mplot3d
from matplotlib import pyplot

# Create a new plot
figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

# Load the STL files and add the vectors to the plot
your_mesh = mesh.Mesh.from_file('tests/stl_binary/HalfDonut.stl')
axes.add_collection3d(mplot3d.art3d.Poly3DCollection(your_mesh.vectors))

# Auto scale to the mesh size
scale = your_mesh.points.flatten()
axes.auto_scale_xyz(scale, scale, scale)

# Show the plot to the screen
pyplot.show()

.. _numpy: http://numpy.org/ .. _matplotlib: http://matplotlib.org/ .. _python-utils: https://github.com/WoLpH/python-utils

Modifying Mesh objects

.. code-block:: python

from stl import mesh
import math
import numpy

# Create 3 faces of a cube
data = numpy.zeros(6, dtype=mesh.Mesh.dtype)

# Top of the cube
data['vectors'][0] = numpy.array([[0, 1, 1],
                                  [1, 0, 1],
                                  [0, 0, 1]])
data['vectors'][1] = numpy.array([[1, 0, 1],
                                  [0, 1, 1],
                                  [1, 1, 1]])
# Front face
data['vectors'][2] = numpy.array([[1, 0, 0],
                                  [1, 0, 1],
                                  [1, 1, 0]])
data['vectors'][3] = numpy.array([[1, 1, 1],
                                  [1, 0, 1],
                                  [1, 1, 0]])
# Left face
data['vectors'][4] = numpy.array([[0, 0, 0],
                                  [1, 0, 0],
                                  [1, 0, 1]])
data['vectors'][5] = numpy.array([[0, 0, 0],
                                  [0, 0, 1],
                                  [1, 0, 1]])

# Since the cube faces are from 0 to 1 we can move it to the middle by
# substracting .5
data['vectors'] -= .5

# Generate 4 different meshes so we can rotate them later
meshes = [mesh.Mesh(data.copy()) for _ in range(4)]

# Rotate 90 degrees over the Y axis
meshes[0].rotate([0.0, 0.5, 0.0], math.radians(90))

# Translate 2 points over the X axis
meshes[1].x += 2

# Rotate 90 degrees over the X axis
meshes[2].rotate([0.5, 0.0, 0.0], math.radians(90))
# Translate 2 points over the X and Y points
meshes[2].x += 2
meshes[2].y += 2

# Rotate 90 degrees over the X and Y axis
meshes[3].rotate([0.5, 0.0, 0.0], math.radians(90))
meshes[3].rotate([0.0, 0.5, 0.0], math.radians(90))
# Translate 2 points over the Y axis
meshes[3].y += 2


# Optionally render the rotated cube faces
from matplotlib import pyplot
from mpl_toolkits import mplot3d

# Create a new plot
figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

# Render the cube faces
for m in meshes:
    axes.add_collection3d(mplot3d.art3d.Poly3DCollection(m.vectors))

# Auto scale to the mesh size
scale = numpy.concatenate([m.points for m in meshes]).flatten()
axes.auto_scale_xyz(scale, scale, scale)

# Show the plot to the screen
pyplot.show()

Extending Mesh objects

.. code-block:: python

from stl import mesh
import math
import numpy

# Create 3 faces of a cube
data = numpy.zeros(6, dtype=mesh.Mesh.dtype)

# Top of the cube
data['vectors'][0] = numpy.array([[0, 1, 1],
                                  [1, 0, 1],
                                  [0, 0, 1]])
data['vectors'][1] = numpy.array([[1, 0, 1],
                                  [0, 1, 1],
                                  [1, 1, 1]])
# Front face
data['vectors'][2] = numpy.array([[1, 0, 0],
                                  [1, 0, 1],
                                  [1, 1, 0]])
data['vectors'][3] = numpy.array([[1, 1, 1],
                                  [1, 0, 1],
                                  [1, 1, 0]])
# Left face
data['vectors'][4] = numpy.array([[0, 0, 0],
                                  [1, 0, 0],
                                  [1, 0, 1]])
data['vectors'][5] = numpy.array([[0, 0, 0],
                                  [0, 0, 1],
                                  [1, 0, 1]])

# Since the cube faces are from 0 to 1 we can move it to the middle by
# substracting .5
data['vectors'] -= .5

cube_back = mesh.Mesh(data.copy())
cube_front = mesh.Mesh(data.copy())

# Rotate 90 degrees over the X axis followed by the Y axis followed by the
# X axis
cube_back.rotate([0.5, 0.0, 0.0], math.radians(90))
cube_back.rotate([0.0, 0.5, 0.0], math.radians(90))
cube_back.rotate([0.5, 0.0, 0.0], math.radians(90))

cube = mesh.Mesh(numpy.concatenate([
    cube_back.data.copy(),
    cube_front.data.copy(),
]))

# Optionally render the rotated cube faces
from matplotlib import pyplot
from mpl_toolkits import mplot3d

# Create a new plot
figure = pyplot.figure()
axes = mplot3d.Axes3D(figure)

# Render the cube
axes.add_collection3d(mplot3d.art3d.Poly3DCollection(cube.vectors))

# Auto scale to the mesh size
scale = cube_back.points.flatten()
axes.auto_scale_xyz(scale, scale, scale)

# Show the plot to the screen
pyplot.show()

Creating Mesh objects from a list of vertices and faces

.. code-block:: python

import numpy as np
from stl import mesh

# Define the 8 vertices of the cube
vertices = np.array([\
    [-1, -1, -1],
    [+1, -1, -1],
    [+1, +1, -1],
    [-1, +1, -1],
    [-1, -1, +1],
    [+1, -1, +1],
    [+1, +1, +1],
    [-1, +1, +1]])
# Define the 12 triangles composing the cube
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]])

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

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

Evaluating Mesh properties (Volume, Center of gravity, Inertia)

.. code-block:: python

import numpy as np
from stl import mesh

# Using an existing closed stl file:
your_mesh = mesh.Mesh.from_file('some_file.stl')

volume, cog, inertia = your_mesh.get_mass_properties()
print("Volume                                  = {0}".format(volume))
print("Position of the center of gravity (COG) = {0}".format(cog))
print("Inertia matrix at expressed at the COG  = {0}".format(inertia[0,:]))
print("                                          {0}".format(inertia[1,:]))
print("                                          {0}".format(inertia[2,:]))

Combining multiple STL files

.. code-block:: python

import math
import stl
from stl import mesh
import numpy


# find the max dimensions, so we can know the bounding box, getting the height,
# width, length (because these are the step size)...
def find_mins_maxs(obj):
    minx = obj.x.min()
    maxx = obj.x.max()
    miny = obj.y.min()
    maxy = obj.y.max()
    minz = obj.z.min()
    maxz = obj.z.max()
    return minx, maxx, miny, maxy, minz, maxz


def translate(_solid, step, padding, multiplier, axis):
    if 'x' == axis:
        items = 0, 3, 6
    elif 'y' == axis:
        items = 1, 4, 7
    elif 'z' == axis:
        items = 2, 5, 8
    else:
        raise RuntimeError('Unknown axis %r, expected x, y or z' % axis)

    # _solid.points.shape == [:, ((x, y, z), (x, y, z), (x, y, z))]
    _solid.points[:, items] += (step * multiplier) + (padding * multiplier)


def copy_obj(obj, dims, num_rows, num_cols, num_layers):
    w, l, h = dims
    copies = []
    for layer in range(num_layers):
        for row in range(num_rows):
            for col in range(num_cols):
                # skip the position where original being copied is
                if row == 0 and col == 0 and layer == 0:
                    continue
                _copy = mesh.Mesh(obj.data.copy())
                # pad the space between objects by 10% of the dimension being
                # translated
                if col != 0:
                    translate(_copy, w, w / 10., col, 'x')
                if row != 0:
                    translate(_copy, l, l / 10., row, 'y')
                if layer != 0:
                    translate(_copy, h, h / 10., layer, 'z')
                copies.append(_copy)
    return copies

# Using an existing stl file:
main_body = mesh.Mesh.from_file('ball_and_socket_simplified_-_main_body.stl')

# rotate along Y
main_body.rotate([0.0, 0.5, 0.0], math.radians(90))

minx, maxx, miny, maxy, minz, maxz = find_mins_maxs(main_body)
w1 = maxx - minx
l1 = maxy - miny
h1 = maxz - minz
copies = copy_obj(main_body, (w1, l1, h1), 2, 2, 1)

# I wanted to add another related STL to the final STL
twist_lock = mesh.Mesh.from_file('ball_and_socket_simplified_-_twist_lock.stl')
minx, maxx, miny, maxy, minz, maxz = find_mins_maxs(twist_lock)
w2 = maxx - minx
l2 = maxy - miny
h2 = maxz - minz
translate(twist_lock, w1, w1 / 10., 3, 'x')
copies2 = copy_obj(twist_lock, (w2, l2, h2), 2, 2, 1)
combined = mesh.Mesh(numpy.concatenate([main_body.data, twist_lock.data] +
                                    [copy.data for copy in copies] +
                                    [copy.data for copy in copies2]))

combined.save('combined.stl', mode=stl.Mode.ASCII)  # save as ASCII

Known limitations

• When speedups are enabled the STL name is automatically converted to lowercase.