[Bf-education] how to catch cheaters in a class?

Mike Pan mike.c.pan at gmail.com
Thu May 25 00:12:24 CEST 2017

Very interesting question...

You can certainly build an addon that saves a random string of some sort
into the Blend file. Or even something that tracks the originating computer
name and total time spent editing the file (to prevent copy+paste from
blendswap/turbosquid) but the students can always 'forget' to use the
correct blend version or the addon.

I think a more fool-proof approach might be to analyze the students' files
based on a bunch of heuristics. This way, the blender file doesn't have to
be special, but you can still catch copycats.  Here are some things you can
look at:
- Datablock names. Especially mesh, material and image names, which is
something many people don't bother changing.
- Node positions. Even if the material is identical, chances are the nodes
are arranged differently. (unless they are using the material panel to
generate all the nodes)
- Look at exact value of properties? (eg. If both students are using a
particle system, unlikely they are both emitting exactly 2740 particles
from frame 77-333)
- if an image texture has been packed and not "made relative" yet, it might
contain the full path of the image, which is telling if it originated from
another user/computer.

That's all i can think of for now. Hope that helps,


On Wed, 24 May 2017 at 12:14 Piotr Arłukowicz <piotao at gmail.com> wrote:

> Hi all,
> is there any way for a teacher to tell whether or not some files in the
> class, which were collected from an assignment, are copied from the same
> person or were created on the same computer?
> I have classes and I have collected quite a few blend files to check. They
> are similar in few areas, so I'm unsure if they were created by different
> persons.
> To solve this problem Julian wrote a small patch few years ago which
> stored a random number inside blend file (so I could at least tell if
> somebody copied somebody's else work and modified it slightly), but
> unfortunately I've got a bunch of files made in just an ordinary, brand
> blender release 2.78.
> Files from students are suspiciously similar (for example a manipulator is
> often set to rotate, not translate).
> So, is there ANY way to tell?
> If not, it could be a good idea to introduce just a random number or
> microsecond stored when file is created and then never changed. This small
> thing could make life easier and could also detects nasty cheating, which,
> unfortunately happens too often in some countries :(
> anybody?
> regards
> pio
> pz
> piotr
> --
> Piotr Arlukowicz
> Version: 3.1
> GCS/ED/IT/S d++(-)>--pu s(+):(+)> a C++(+++)$@>++++$  ULAVISC*()$>+++$
> P++(+++)$>++++ L++(+++)$@>++++$ !E---(---)>++ W++(+++)$@>+++ N(+)>++ o--?
> !K-(-)>-$ w++(+)>-- !O-(-)>- !M-(-)>-- !V-(-)>- PS(+)>++ !PE()>+  Y PGP>+
> t(-) !5? !X R()>* tv- b++ DI++ D+(++)>+++ G++@ e++++>+++++ h---()>++ r+++
> y+++
> ------END GEEK CODE BLOCK------
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