Mighty SysAdmins

It has been some time now since I first used university servers for Blender or Yafray renderings. 🙂

I have an account on these ones:

  • server1: 2 x Xeon 2.8GHz and 3GB RAM
  • server2: 4 x Xeon 3.2Ghz and 4GB RAM
  • server3: 4 x Xeon 3.4GHz and 4GB RAM

The first one is accessible from the outside, then you can log in the other two, which are serving our computer labs.

Servers Room

But as soon as I was just wetting my appetite I faced a serious problem, for long renderings the renderer process got killed unexpectedly.
The first thing that came up to my mind was a kind of cpu limitation, but both /etc/limits and /etc/security/limits.conf had all the lines commented out and no PAM module was loaded in the kernel.

Today I just discovered that is a lot simple if you just run ulimit -t, instead of inspecting system configuration files. 🙂
This way I discovered that there is a 1s limit for server2 (that as a matter of facts was quite unusable for anything serious), 1000s for server3 and unlimited for server 1 (but it runs net daemons so it’s a lot more controlled than the other two). 🙁

I feel defeated by the mighty power of the root user, who, as a demiurge, can choose everything and enforce his wills with unbreakabre rules. 🙁
As if the cpu limitation were not enough, today I’ve also spotted one of the roots encoding a mpeg file of “Young Frankenstein” in xvid with mencoder!
Why he can use a university server for a task as personal as encoding a movie (forget for a moment about any legal issue…) while me, a student who pays for education, cannot use it for something as noble as learning computer graphics?

While overwhelmed by these thoughts I had a nice idea, to render with Yafray’s regions option and compose pieces with ImageMagick:

  • nice ./yafray -c 4 -r -1:1:-1:0 /tmp/YBtest.xml
  • mv /tmp/YBtest.tga /tmp/YBtest1.tga
  • nice ./yafray -c 4 -r -1:1:0:1 /tmp/YBtest.xml
  • mv /tmp/YBtest.tga /tmp/YBtest2.tga
  • composite -compose difference tmp/YBtest1.tga tmp/YBtest2.tga YBtest.png

Actually -compose difference just ignores black regions, and this can lead to wrong results, I should find in composite manual a compose operator that works with image coordinates.

I’m too lazy for it, but I’m sure it’s possible to automatize the task of region subdivisions using a recursive script that splits every region that cannot be rendered in less than 1000s…
But anyway, mission accomplished! 😉

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