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

Piotr Arłukowicz piotao at inf.ug.edu.pl
Thu May 25 07:52:51 CEST 2017

Thanks Mike,
in fact, I already was forced to do such 'heuristics', because lots of
files were 'too' similar.

However, in case of animation this is rather hard to tell, especially when
students are opening the same file with assignment. I could potentially
solve that telling them to import rather than open, and then such lovely
random string or just something (creation timestamp?) will be a nice
addition to the normal Blender.
How many teachers are still here? Don't have any of you cheating problems?

Maybe it's a good idea to create such a plugin, where student can 'submit'
the work right from Blender...


Piotr Arłukowicz, PhD, BFCT
University of Gdańsk, Faculty of Mathematics, Physics and Informatics,
Dept. of AI,
Wit Stwosz 57, 80-952 Gdańsk, room 121, tel.: +48585232151,
Polish Blender Course: http://polskikursblendera.pl/ [PL]

2017-05-25 0:12 GMT+02:00 Mike Pan <mike.c.pan at gmail.com>:

> 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,
> Mike
> 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*()$>+++$
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>> !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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