Mesh Operations

Rotation

Rotate around an arbitrary axis:

import math
from stl import mesh

m = mesh.Mesh.from_file('model.stl')

# Rotate 90 degrees around the Y axis
m.rotate([0, 0.5, 0], math.radians(90))

# Rotate around an axis passing through a specific point
m.rotate([0, 0, 1], math.radians(45), point=[1, 0, 0])

Translation

Translate (move) a mesh:

from stl import mesh

m = mesh.Mesh.from_file('model.stl')
m.translate([10, 0, 5])

You can also modify coordinates directly:

m.x += 10  # shift all X coordinates
m.y += 5   # shift all Y coordinates

Transformation (4x4 Matrix)

Apply a full 4x4 transformation matrix:

import numpy as np
from stl import mesh

m = mesh.Mesh.from_file('model.stl')

# Rotate 90 degrees around Z and translate by [10, 0, 5]
matrix = np.eye(4)
matrix[:3, :3] = [
    [0.0, -1.0, 0.0],
    [1.0, 0.0, 0.0],
    [0.0, 0.0, 1.0],
]
matrix[:3, 3] = [10.0, 0.0, 5.0]
m.transform(matrix)

Combining Meshes

Concatenate mesh data arrays to combine meshes:

import numpy as np
from stl import mesh

m1 = mesh.Mesh.from_file('part1.stl')
m2 = mesh.Mesh.from_file('part2.stl')

combined = mesh.Mesh(np.concatenate([m1.data, m2.data]))
combined.save('combined.stl')

Removing Duplicates

Remove duplicate or degenerate triangles:

from stl import mesh, base

m = mesh.Mesh.from_file('model.stl')

# Remove duplicate triangles (keep one copy)
data = mesh.Mesh.remove_duplicate_polygons(
    m.data,
    base.RemoveDuplicates.SINGLE,
)

# Remove zero-area triangles
data = mesh.Mesh.remove_empty_areas(data)
cleaned = mesh.Mesh(data)