Skip to content

Instantly share code, notes, and snippets.

@xeyvezy
Forked from balazsdukai/objsplit.py
Created November 10, 2020 01:15
Show Gist options
  • Select an option

  • Save xeyvezy/32cf9c6654f8639ca7734c424fc35781 to your computer and use it in GitHub Desktop.

Select an option

Save xeyvezy/32cf9c6654f8639ca7734c424fc35781 to your computer and use it in GitHub Desktop.
Split an OBJ file into separate files per named object
#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""Split an OBJ file into separate files per named object
Ignores vertex texture coordinates, polygon groups, parameter space vertices.
The individual files are named as the object they contain. The material file
(.mtl) is not split with the objects.
Run:
$ objsplit.py /input/dir/file.obj /output/dir
Written by Balázs Dukai, https://github.com/balazsdukai
"""
import re
import os.path as p
import sys
from contextlib import contextmanager
import os
@contextmanager
def suppress_stdout():
with open(os.devnull, "w") as devnull:
old_stdout = sys.stdout
sys.stdout = devnull
try:
yield
finally:
sys.stdout = old_stdout
def main(file_in, dir_out):
v_pat = re.compile(r"^v\s[\s\S]*") # vertex
vn_pat = re.compile(r"^vn\s[\s\S]*") # vertex normal
f_pat = re.compile(r"^f\s[\s\S]*") # face
o_pat = re.compile(r"^o\s[\s\S]*") # named object
ml_pat = re.compile(r"^mtllib[\s\S]*") # .mtl file
mu_pat = re.compile(r"^usemtl[\s\S]*") # material to use
s_pat = re.compile(r"^s\s[\s\S]*") # shading
vertices = ['None'] # because OBJ has 1-based indexing
v_normals = ['None'] # because OBJ has 1-based indexing
objects = {}
faces = []
mtllib = None
usemtl = None
shade = None
o_id = None
with open(file_in, 'r') as f_in:
for line in f_in:
v = v_pat.match(line)
o = o_pat.match(line)
f = f_pat.match(line)
vn = vn_pat.match(line)
ml = ml_pat.match(line)
mu = mu_pat.match(line)
s = s_pat.match(line)
if v:
vertices.append(v.group())
elif vn:
v_normals.append(vn.group())
elif o:
if o_id:
objects[o_id] = {'faces': faces,
'usemtl': usemtl,
's': shade}
o_id = o.group()
faces = []
else:
o_id = o.group()
elif f:
faces.append(f.group())
elif mu:
usemtl = mu.group()
elif s:
shade = s.group()
elif ml:
mtllib = ml.group()
else:
# ignore vertex texture coordinates, polygon groups, parameter
# space vertices
pass
if o_id:
objects[o_id] = {'faces': faces,
'usemtl': usemtl,
's': shade}
else:
sys.exit("Cannot split an OBJ without named objects in it!")
# vertex indices of a face
fv_pat = re.compile(r"(?<= )\b[0-9]+\b", re.MULTILINE)
# vertex normal indices of a face
fn_pat = re.compile(r"(?<=\/)\b[0-9]+\b(?=\s)", re.MULTILINE)
for o_id in objects.keys():
faces = ''.join(objects[o_id]['faces'])
f_vertices = {int(v) for v in fv_pat.findall(faces)}
f_vnormals = {int(vn) for vn in fn_pat.findall(faces)}
# vertex mapping to a sequence starting with 1
v_map = {str(v): str(e) for e, v in enumerate(f_vertices, start=1)}
vn_map = {str(vn): str(e) for e, vn in enumerate(f_vnormals, start=1)}
faces_mapped = re.sub(fv_pat, lambda x: v_map[x.group()], faces)
faces_mapped = re.sub(
fn_pat, lambda x: vn_map[x.group()], faces_mapped)
objects[o_id]['vertices'] = f_vertices
objects[o_id]['vnormals'] = f_vnormals
# old vertex indices are not needed anymore
objects[o_id]['faces'] = faces_mapped
oid_pat = re.compile(r"(?<=o\s).+")
with suppress_stdout():
for o_id in objects.keys():
fname = oid_pat.search(o_id).group()
file_out = p.join(dir_out, fname + ".obj")
with open(file_out, 'w', newline=None) as f_out:
if mtllib:
f_out.write(mtllib)
f_out.write(o_id)
for vertex in objects[o_id]['vertices']:
print(vertex)
f_out.write(vertices[int(vertex)])
for normal in objects[o_id]['vnormals']:
f_out.write(v_normals[int(normal)])
if objects[o_id]['usemtl']:
f_out.write(objects[o_id]['usemtl'])
if objects[o_id]['s']:
f_out.write(objects[o_id]['s'])
f_out.write(objects[o_id]['faces'])
if __name__ == '__main__':
file_in = sys.argv[1]
dir_out = sys.argv[2]
main(file_in, dir_out)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment