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from __future__ import absolute_import
import math
import struct
ASCII_FACET = """facet normal {normal[0]:.4f} {normal[1]:.4f} {normal[2]:.4f}
outer loop
vertex {face[0][0]:.4f} {face[0][1]:.4f} {face[0][2]:.4f}
vertex {face[1][0]:.4f} {face[1][1]:.4f} {face[1][2]:.4f}
vertex {face[2][0]:.4f} {face[2][1]:.4f} {face[2][2]:.4f}
endloop
endfacet
"""
BINARY_HEADER ="80sI"
BINARY_FACET = "12fH"
def crossproduct(u,v):
s1 = u[1]*v[2] - u[2]*v[1]
s2 = u[2]*v[0] - u[0]*v[2]
s3 = u[0]*v[1] - u[1]*v[0]
return [s1, s2, s3]
def norm(v):
return math.sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
def normalize(v):
m = norm(v)
return [v[0]/m, v[1]/m, v[2]/m]
def normalto(u,v):
return normalize(crossproduct(u,v))
def diff(u,v):
return [u[0]-v[0], u[1]-v[1], u[2]-v[2]]
#functions for calculation of the normal vector (right-thumb-rule)
def crossProduct(a, b):
#calculate cross product of two threedimensional vectors
if (len(a)!=3) or (len(b)!=3):
raise ValueError('unvalid value')
return [a[1]*b[2] - a[2]*b[1], a[2]*b[0] - a[0]*b[2], a[0]*b[1] - a[1]*b[0]]
def diff(v1,v2):
#substracting one list from another
if (len(v1)!=3) or (len(v2)!=3):
raise ValueError('unvalid value')
return [v1[0]-v2[0],v1[1]-v2[1],v1[2]-v2[2]]
def normal(v1,v2,v3):
#calculate normal vector on triangle spanned by the three vertices
#tells in which direction the plane looks "right-thumb-rule"
if (len(v1)!=3) or (len(v2)!=3) or (len(v2)!=3):
raise ValueError('unvalid value')
n=crossProduct(diff(v2,v1),diff(v3,v1))
absolut=0
for i in n:
if i>=0:
absolut+=i
else:
absolut-=i
if absolut == 0:
#print "this should not have happened!"
return n
else :
return [n[0]/absolut,n[1]/absolut,n[2]/absolut]
#simple function to create sets of three vertices
def triangulate(vertices):
n=len(vertices)
if(n==3):
return vertices
elif n < 3:
facets = triangulate(facet)
self.add_facets(facets)
else:
raise ValueError('wrong number of vertices')
def add_facets(self, facets):
#print "add %d facets" % len(facets)
for facet in facets:
self.add_facet(facet)
def extrude(self,bottom,height):
if len(bottom) < 3 :
raise ValueError('not a polygon')
else :
top = []
for vertice in bottom :
top.append([vertice[0],vertice[1],vertice[2]+height])
bottom.reverse()
self.add_facet(bottom)
bottom.reverse()
for i in range(0,len(bottom)-1) :
self.add_facet([bottom[i],bottom[i+1],top[i+1],top[i]])
self.add_facet([bottom[len(bottom)-1],bottom[0],top[0],top[len(bottom)-1]])
self.add_facet(top)
class ASCII_STL_Writer:
""" Export 3D objects build of 3 or 4 vertices as ASCII STL file.
"""
def __init__(self, stream):
self.fp = stream
self._write_header()
def _write_header(self):
self.fp.write("solid python\n")
def close(self):
self.fp.write("endsolid python\n")
def _write(self, face):
n = normalto(diff(face[0],face[1]),diff(face[1],face[2]))
self.fp.write(ASCII_FACET.format(normal=n,face=face))
def _split(self, face):
p1, p2, p3, p4 = face
return (p1, p2, p3), (p3, p4, p1)
def add_face(self, face):
""" Add one face with 3 or 4 vertices. """
if len(face) == 4:
face1, face2 = self._split(face)
self._write(face1)
self._write(face2)
elif len(face) == 3:
self._write(face)
else:
raise ValueError('only 3 or 4 vertices for each face')
def add_faces(self, faces):
""" Add many faces. """
for face in faces:
self.add_face(face)
class Binary_STL_Writer(ASCII_STL_Writer):
""" Export 3D objects build of 3 or 4 vertices as binary STL file.
"""
def __init__(self, stream):
self.counter = 0
ASCII_STL_Writer.__init__(self,stream)
def close(self):
self._write_header()
def _write_header(self):
self.fp.seek(0)
self.fp.write(struct.pack(BINARY_HEADER, b'Python Binary STL Writer', self.counter))
def _write(self, face):
self.counter += 1
n = normalto(diff(face[0],face[1]),diff(face[1],face[2]))
data = [
n[0], n[1], n[2],
face[0][0], face[0][1], face[0][2],
face[1][0], face[1][1], face[1][2],
face[2][0], face[2][1], face[2][2],
0
]
self.fp.write(struct.pack(BINARY_FACET, *data))
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