I have noticed several behaviours in Blender that are different depending on whether the full UI is used, or if Blender is being automated 'headless' using a script on the command line.

By 'headless', I refer to using a command such as:

$ ./blender -b <file.blend> -P <script.py>


My test directory starts with these files:

-rw-r--r-- 1 doug doug 67 2010-10-20 18:50 save_as_new.py
-rw-r--r-- 1 doug doug 397124 2010-10-20 18:45 cube_offorigin_start.blend

cube_offorigin_start.blend is a scene that contains a single Cube object that is located away from the world origin.


First of all, when compiling a test script for this bug report another bug surfaced, so I'll report that first.

save_as_new.py currently contains this code:

import bpy
bpy.ops.wm.save_as_mainfile( filepath='TEST1.blend' )


1. bpy.ops.wm.save_as_mainfile() created a junk file in the cwd
$ ../blender/blender -b cube_offorigin_start.blend -P save_as_new.py
found bundled python: /home/doug/Development/blender/install/linux2/2.54/python
read blend: /home/doug/blender_debug/cube_offorigin_start.blend
*bpy stats* - tot exec: 6, tot run: 0.0016sec, average run: 0.000259sec, tot usage 3.0023%

Blender quit
$ ls -l
-rw-r--r-- 1 doug doug 67 2010-10-20 18:50 save_as_new.py
-rw-r--r-- 1 doug doug 397124 2010-10-20 18:45 cube_offorigin_start.blend
-rw-r--r-- 1 doug doug 12 2010-10-20 18:56 ~ș?d?
-rw-r--r-- 1 doug doug 311648 2010-10-20 18:56 TEST1.blend
$ cat \~ș�d^?
TEST1.blend
$

Most odd.


My original bug report was about the object align operator:

2. use_align_operator.py:
import bpy

for obj in bpy.data.objects: obj.select = False
bpy.data.objects['Cube'].select = True

bpy.ops.object.align(
align_mode = 'OPT_1', # Negative
relative_to = 'OPT_1', # World origin
align_x = True, align_y = True, align_z = True
)

bpy.ops.wm.save_as_mainfile( filepath='cube_align_operator.blend' )

$ ../blender/blender -b cube_offorigin_start.blend -P use_align_operator.py
found bundled python: /home/doug/Development/blender/install/linux2/2.54/python
read blend: /home/doug/blender_debug/cube_offorigin_start.blend
Traceback (most recent call last):
File "/home/doug/Development/blender/install/linux2/2.54/scripts/op/object_align.py", line 271, in execute
align_objects(self.align_x, self.align_y, self.align_z, self.align_mode, self.relative_to)
File "/home/doug/Development/blender/install/linux2/2.54/scripts/op/object_align.py", line 34, in align_objects
for obj in bpy.context.selected_objects:
AttributeError: 'Context' object has no attribute 'selected_objects'
*bpy stats* - tot exec: 6, tot run: 0.0022sec, average run: 0.000366sec, tot usage 4.2089%
Error Totblock: 9
wmOperatorReportList len: 40 0x290c0b8
OBJECT_OT_align len: 168 0x2a081a8
wmOperatorPtrRNA len: 24 0x2f72478
IDProperty array dup len: 96 0x2a08298
IDProperty array dup len: 96 0x2a08348
IDProperty array dup len: 96 0x2a083f8
IDProperty array dup len: 96 0x2a084a8
IDProperty array dup len: 96 0x2a08558
IDProperty array dup len: 96 0x2a08608

Blender quit
$ ls -l
-rw-r--r-- 1 doug doug 311648 2010-10-20 19:02 cube_align_operator.blend
-rw-r--r-- 1 doug doug 397124 2010-10-20 18:45 cube_offorigin_start.blend
-rw-r--r-- 1 doug doug 67 2010-10-20 19:00 save_as_new.py
-rw-r--r-- 1 doug doug 12 2010-10-20 18:56 ~ș?d?
-rw-r--r-- 1 doug doug 311648 2010-10-20 18:56 TEST1.blend
-rw-r--r-- 1 doug doug 26 2010-10-20 19:02 tor.blen ?3?b?
-rw-r--r-- 1 doug doug 315 2010-10-20 19:01 use_align_operator.py

The Cube in cube_align_operator.blend is not aligned as expected - it has not moved at all.


I have been writing another script in which setting an object's location like this:
MY_OBJ.location = [0,0,0]
hasn't worked either, but I'm currently unable to reproduce that in a debug environment outside of that script.


I've attached a tar.gz containing all the files I used and created in this report.