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#!/usr/bin/env python
#
# OpenSCAD produces randomly ordered STL files so source control like GIT can't tell if they have changed or not.
# This scrip orders each triangle to start with the lowest vertex first (comparing x, then y, then z)
# It then sorts the triangles to start with the one with the lowest vertices first (comparing first vertex, second, then third)
# This has no effect on the model but makes the STL consistent. I.e. it makes a canonical form.
#
from __future__ import print_function
import sys
class Vertex:
def __init__(self, x, y, z):
self.x, self.y, self.z = x, y, z
self.key = (float(x), float(y), float(z))
class Normal:
def __init__(self, dx, dy, dz):
self.dx, self.dy, self.dz = dx, dy, dz
class Facet:
def __init__(self, normal, v1, v2, v3):
self.normal = normal
if v1.key < v2.key:
if v1.key < v3.key:
self.vertices = (v1, v2, v3) #v1 is the smallest
else:
self.vertices = (v3, v1, v2) #v3 is the smallest
else:
if v2.key < v3.key:
self.vertices = (v2, v3, v1) #v2 is the smallest
else:
self.vertices = (v3, v1, v2) #v3 is the smallest
def key(self):
return (self.vertices[0].x, self.vertices[0].y, self.vertices[0].z,
self.vertices[1].x, self.vertices[1].y, self.vertices[1].z,
self.vertices[2].x, self.vertices[2].y, self.vertices[2].z)
class STL:
def __init__(self, fname):
self.facets = []
f = open(fname)
words = [s.strip() for s in f.read().split()]
f.close()
if words[0] == 'solid' and words[1] == 'OpenSCAD_Model':
i = 2
while words[i] == 'facet':
norm = Normal(words[i + 2], words[i + 3], words[i + 4])
v1 = Vertex(words[i + 8], words[i + 9], words[i + 10])
v2 = Vertex(words[i + 12], words[i + 13], words[i + 14])
v3 = Vertex(words[i + 16], words[i + 17], words[i + 18])
i += 21
self.facets.append(Facet(norm, v1, v2, v3))
self.facets.sort(key = Facet.key)
else:
print("Not an OpenSCAD ascii STL file")
sys.exit(1)
def write(self, fname):
f = open(fname,"wt")
print('solid OpenSCAD_Model', file=f)
for facet in self.facets:
print(' facet normal %s %s %s' % (facet.normal.dx, facet.normal.dy, facet.normal.dz), file=f)
print(' outer loop', file=f)
for vertex in facet.vertices:
print(' vertex %s %s %s' % (vertex.x, vertex.y, vertex.z), file=f)
print(' endloop', file=f)
print(' endfacet', file=f)
print('endsolid OpenSCAD_Model', file=f)
f.close()
def canonicalise(fname):
stl = STL(fname)
stl.write(fname)
if __name__ == '__main__':
if len(sys.argv) == 2:
canonicalise(sys.argv[1])
else:
print("usage: c14n_stl file")
sys.exit(1)