To the core Blender developers.
Hello again, Collection Manager dev here.
Let me start off by saying that I care a lot about Blender, it's
been a
huge influence on my life and an inspiring story of the little DCC
app
that could, and I want nothing but the best for it. So it highly
saddens
me that I feel I need to write this email.
I've been a part of the Blender community and writing add-ons for it
for
eight years and a user of Blender for even longer. I love the power
it
gives me to create, and have always tried to give back with what I
have
to give (Unfortunately, money is not one of those ways, so I have
contributed code, feedback, and support instead).
In 2019 I separated the Collection Manager out of a larger add-on
and
submitted it to be included in Blender as a bundled add-on on the
advice
of Brendon Murphy (meta-androcto). Soon after my submission, I was
contacted by Paul Kotelevets (1D_Inc) who expressed the short
comings of
the current collections system for complex scene setup and precise
modeling that requires multiple reference images. Together, along
with
others who gave feedback, we have advanced the usability of Blender
for
complex setups and increased the capabilities of the new collection
system. When I started this project I assumed that it would be
highly
welcomed, because collections were one of the pillars of the 2.8
project, however, it was mostly ignored. Still, I continued on with
the
project because it was useful to me and was essential to others for
their jobs.
In the year and a half I've worked on the project, I've become
pretty
familiar with the python side of collections and layer collections,
but
during that time I ran into problems that I thought would be better
solved on the C side of Blender, so I spent ~6 months familiarizing
myself with layer collections and attempting to solve some of the
problems I'd run into, and then ultimately trying to stabilize layer
collections as a first step to further improvements. I submitted
three
patches during this time, one of which went nowhere (and rightly
so),
one of which was a draft and that I used to ask for help when stuck
(to
which was replied: Thanks for the patch, but it's up to you to
present a
working code, otherwise it's likely a loss of time for
everybody...),
and then a final one, which did contain working code.
I submitted the final patch on November 18th 2020 and assigned
Bastien
Montagne, Brecht Van Lommel, and Dalai Felinto as reviewers; two
months
later I updated the patch to the latest master and linked a good
test
file I had made; ~2 weeks after that, Bastien responded that the
patch
hadn't been forgotten and that he'd just had a lot on his plate; a
few
days after this Hans Goudey (HooglyBoogly) reviewed the patch and
provided some really good comments (he didn't have to do this and
I'm
really grateful to him), which I then addressed a couple weeks later
(I
had been busy and things didn't seem urgent); three months later I
updated the patch to the latest master again; and then almost two
months
after that it was abandoned by Bastien who had apparently just
committed
his own solution.
As you might imagine, this was fairly distressing to me as I had put
a
lot of time and effort into creating and then maintaining it. I had
been content to be patient and not push for my patch, because I
thought
it was of a low priority and I knew from various sources of Blender
communication that Bastien had been very busy and I didn't want to
add
to the stress he was under. So, after the patch was closed, I
looked
into the one that replaced it and at Bastien's weekly reports to try
and
figure out what had happened.
On inspection of Bastien's weekly reports, I found that he had been
working on his own solution for a month or so, but I hadn't
connected
the dots because I thought he was working on stuff for library
overrides
and that if he had needed something to preserve layer collections he
would have used the already working code that had been sitting in
the
patch tracker for six months (or if a different direction was
required,
told me and brought me onboard with developing the new patch). And
when
I looked at the patch that replaced mine, I found a comment by
Brecht
saying it was "Great to see this tackled.", as if now that a "real"
programmer was working on it, it was suddenly much more important
and
welcomed.
There are two issues here, with the first being how everything was
handled, the lack of communication and the disregard for the time I
spent attempting to contribute. I have seen in official Blender
communications that one of the goals of Blender is to onboard new
developers, this is a perfect example of how not to do that.
Campbell
Barton once said something in IRC about GSoC students that I have
always
found inspiring:
"Typically for students who don't know what they want they ask a lot
of
Q's... and never get involved.
(sounds a bit negative... just my experience tho)
Basically they waste our time.
People who are motivated don't wait for others to tell them what to
do,
they start interesting projects themselves."
Now I'm not a GSoC student, but I started an interesting project,
and
filled a gap that the core developers didn't have the time to
address.
I didn't ask a lot of questions, because I'm pretty good at figuring
things out on my own, and I attempted to get involved. When I
started, I
expected to be welcomed and onboarded by a great open source project
that was in need of more contributors and that I could work with to
improve a tool I care deeply about, but what I found was a project
that
paid little attention to my contributions, did nothing to onboard
me,
seems to care little for community contributions, and was mostly
unwilling to work with me.
The second issue here is with the code of the patch (D12016) that
was
approved over mine (D9599). While as far as I can tell, they are
functionally equivalent, Bastien's is much slower than mine,
especially
when it comes to many layer collections under one parent. From my
tests
(debug, lite build, with Bastien's CLOGGING removed so as to match
my
patch) the average time it took to resync 1000 collections when
configured so that each of the 1000 had 1 child was 612 microseconds
for
Bastien's and 261 microseconds for my patch. That's almost 2.5
times
slower for his patch. When the 1000 collections were configured as
a
flat list under the scene collection, Bastiens took on average 22290
microseconds, while mine, on average, took only 252 microseconds.
That's almost 88.5 times slower for his patch.
You may be thinking that 1000 collections is unrealistically high
and
that no one actually uses that many, but Paul Kotelevets (a diamond
level sponser, BTW) has told me that he regularly uses 7-9,000
collections in his work, so my test case is on the low side and the
performance costs of Bastien's patch will be even greater than what
I
have outlined here.
I believe the performance problems with Bastien's patch stem mainly
from
three places, the BLI_findptr which is used to check whether the
layer
collection is valid as a child when generating the layer collection
tree
wrapper with additional data, the method that is used when searching
through the wrapper, and the fact that each layer collection has to
be
searched out from the wrapper, even when it is already in sync with
the
collection tree. The problem with all this searching is that for
each
collection it tries to find under the current parent it has to loop
over
all the previous collections under that parent, and this happens in
2
distinct areas. And I believe this is also why it's so much slower
when
all the collections are under one parent.
I think the reason mine is so much faster is that it does much less
searching. My patch processes the layer collection tree in a depth
first search and finds only the invalid layer collections and stores
them in order, then the collection tree and layer collection tree
are
walked through in tandem, re-linking the valid layer collections as
it
goes, moving the invalid layer collections to their new positions
when
needed, and then removing the invalid layer collections from the
original processed list after they've been added to the new layer
collection tree. As little searching as possible is done, with the
initial order of the layer collections, the fact that they are
invalid,
and the fact that the collection associated with that layer
collection
matches the collection in the collection tree provides the needed
data
to relink them successfully.
I will admit that there's always the possibility that my patch
doesn't
handle some corner case, but nothing was identified in my own
testing or
the review given to my patch, so I think it's safe to say the only
difference between the two is the underlying method, the
performance,
and the authors.
Given what has happened I'd like to just wash my hands of this and
forget wasting all of our time with me trying to contribute to the C
side of Blender and just stick to developing my add-on for those
that
rely on it, but I can't, the performance implications are too large
and
I can't in good conscience ignore this. I'm willing to try and work
with you on this, whether that's with my patch, or on Bastien's to
improve his patch's performance (if it is uncovered that there is
some
unsolvable limitation with mine), but I hope I have conveyed that a
much
better outcome with much less work for all parties could have been
achieved had I been worked with, instead of around.
Sincerely yours,
an offboarded developer.
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