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Blender Crash with subsurf mod on default cube with huge resolution
Closed, ResolvedPublic


System Information
Debian 7 (64 Bit), 512 GB RAM (GB, not MB), NVidia Quadro K5200

Blender Version
Broken: 2.74 release (Linux 64 Bit)

Short description of error
Blender Crash with Segmentation Fault when using subsurf mod and huge render resolutions

Exact steps for others to reproduce the error

  • Load Factory Settings
  • Enter Redering Resolution x: 50000 px ; y: 25000 px ; scale: 100%
  • add Subdivision Surface Modifier on default cube; set render subdivisions to 3
  • Hit Render Button

-> Crash
Crash log:

When using the attached .blend file, just hit Render Button

If you set even higher resolutions, like 50000 x 40000, rendering starts, but doesn't produce a picture. Instead you get a lot of errors like
"Calloc returns null: len=18446744073119617024 in imbuf display buffer, total 1356434112"
in the terminal.

Event Timeline

Daniel Dreschers (DanD) set Type to Bug.
Daniel Dreschers (DanD) created this task.
Daniel Dreschers (DanD) raised the priority of this task from to Needs Triage by Developer.

Can you try a recent version of blender from buildbot? There have been fixes to support rendering of bigger resolutions.

Antony Riakiotakis (psy-fi) triaged this task as Needs Information from User priority.May 28 2015, 11:32 AM

I downloaded Blender 2.74.5 Hash 3e0c6a8

Unfortunately this version also crashes.
No matter if using the .blend file I attached to the original report, or doing the steps manually.
The only difference is, that the blender window doesn't close this time. Have to use the kill command to get rid of it.

This seems like a regular out-of-memory situation.

While Blender doesn't normally check for this case, it might make sense to do so allocating large buffers (render_layer_add_pass) then fail rendering with an error.

Out of memory?
On a machine with 512 Gigabyte of RAM?

Can I somewhere see, how much memory Blender is trying to allocate?

Doesn't sound like an out of memory, most likely it's an integer overflow due to using int instead of size_t.

So, I'm investigating this here. Indeed there's a deadlock somewhere but increasing the tile size to 256 makes rendering possible here. It's probably caused by an overflow with the tile size somewhere, but at least you should be able to render if you increase the tile size.

Antony Riakiotakis (psy-fi) claimed this task.

Issue is that covering the whole image with 64x64 tiles needs a total of 305762 tiles.

Before rendering we sort those tiles so that the ones closer to the center begin rendering first.

The problem is that sorting those is an 2 * n^2 operation (sort every one of them and for every one of them calculate center of available tiles and find nearest to that center tile). It follows that you are going to wait for 186.980.801.288 * cost of operation per tile time before starting rendering. If we suppose that the cost is one CPU cycle, you still need about one minute for the whole thing to finish (this is not a multithreaded operation). However, this costs quite more than one CPU cycle, and tiles are stored in a linked list, adding multiple cache misses to the cost.

For a tile size of 256, we need roughly 16 times less tiles to cover the grid and 256 times less time before starting rendering. Which is roughly the difference between 2 hours and a minute.

In any case, tested this in our super render farm with 64GB of RAM and after about half an hour or so the file begun rendering.

So, verdict is: this is not a bug, you just need to set tile size higher. I can try to optimize that part a little bit, but best complexity I can do is n * (n + 1) / 2 so don't expect miracles.

In fact if this is plugged to a quicksort, we may even get n log n complexity. But still, it will be quite expensive.

I tried setting the tile size to 256.
It doesn't work.
Blender still crashes here.
Tried 2.74.5 (Hash_3e0c6a8) on my linux machine and 2.74.5 (Hash_dc15860) on my Windows machine.

What you are saying about the complexity of the sorting algorithm would turn out to be a matter waiting.
I wouldn't mind that. I'd get paid for that. ;)
Unfortunately it's not. Blender crashes. I get a segmentation fault and Blender writes out a crash log.

What you described above does not sound like a crash:

"The only difference is, that the blender window doesn't close this time. Have to use the kill command to get rid of it."

This is not a crash, blender is actually computing stuff. If you get a crash (blender closing on its own) then I'm afraid I can't reproduce your issue here.

It would be quite a simple task to investigate the limits of Blender on your super computer.
Just start small and increase sizes in sensible steps, Observe how things take longer and/or what takes suspicious amount of times more.

Antony Riakiotakis (psy-fi) changed the task status from Invalid to Resolved.May 28 2015, 5:07 PM

Hi, tested your file with 64 by 64 tile size in our render farm after my commit and the time difference is immense - render starts after a few seconds now. I will mark as resolved, at least on our side. You can test a build on tomorrow's buildbot and see if the issue still persists there.

Antony, you are correct. It's my lazyness that's now causing confusion.
I omitted to say that when the blender window didn't close, there was a message in the terminal: "Writing: /tmp/blender.crash.txt". That's why I assumed that blender had crashed and I closed it by using kill.

Tested the linux 64 bit build 3511e2d this morning. Crashed again.

But since you can't reproduce this behaviour, I'll keep shut and will try to find another way to reproduce this.

Can blender make PNG file of the size(50000x40000) with your PC?
You can confirm it in Image Editor of blender.
I think that you should check the size that an error does not produce.

Can you try with background rendering? (n fact this is the only way I've tried rendering here because our farm server does not have any screens and I suspect no GPUs either.

The options are:

blender -b <blendfile> -f <frame> -o <imagefile.png>

Can you try removing subsurf and see if it's still impossible to render?
Can you try with even bigger tile sizes and see if the issue is still there?
Lastly, are you certain you are using the correct version of blender when opening those files (ie not running a version in PATH or so)?

sindra: Yes, it is possible to create a 50000x25000 picture in the UV Editor and save it to a file.

Antony: You're again correct. Using the background rendering, it works. Even the default scene at a resolution of 50000x40000 renders correct.
But when using the GUI, it's not.
I tried with and without subsurf modifier. I tried tile sizes from default up to 4096x4096. Every time I got a segmentation fault when using the GUI.

And yes, I am certain I'm using the correct version. I start from a terminal and check the hash at the splash screen every time I do something related to this report.

Since it now seems to be a problem with the GUI, I'm playing around with some settings.
For the test running at the moment, I set "User preferences"-"System"-"Images Draw Method" to "GLSL".
With this setting I noticed the following:
a) it starts rendering
b) when I use the scroll wheel to zoom out of the rendered picture while it is rendering, Blender crashes
c) when I start rendering and don't touch Blender, it runs. At least for the first 30 minutes I let it. Unfortunately I can't block this machine over the weekend. I need it to do something else. But I also noticed, rendering with the GUI is horribly slow with these settings. The background render was done within a few minutes.

(All test from this posts were done with Blender 2.74.5 Hash_3511e2d on Linux 64 Bit.)

Looks like there were indeed some integer overflow cases. Can you check again with buildbot tomorrow?

I don't have access to my big computer over the weekend. I'll have to check on monday.
And I'd like to say thank you for taking the time to look into this problem.

Tested Blender 2.74.5 hash_b147473 today.

Going through the following steps leads to a blender crash.

  • Load Factory Settings
  • Set Render Resolution to X: 50000, Y: 25000, Scale: 100%
  • Hit Render Button

When I switch to "Images Draw Method: GLSL" in "User Preferences" - "System" after loading factory settings, it starts rendering and zooming out works as well.
The only thing I noticed was a slight offset between the orange surroundings of an actively rendered tile and the actual tile that's being displayed (see Screenshot).