Weird gamma(?) issue

[johanboekhoven]

Hi all,

I have a weird problem on our renderfarm. All machines are identical, i7-4770k, 16GbRam on a AsusTek, Z87M-Plus, with max2014 and vray 3.1.0.0.3 (older versions had it too). This machine was completely and cleanly reinstalled, and still the same problem.
All other machines render fine and identical except 1, looks like this machine can't handle transparency well, or is pre-multiplying alpha in a wrong way on a bitmap texture. I'm not sure how to debug this one. Is it vray, is it bitmap texture, is it max or windows. Do I have bad memory in the machine..? I'm not sure.

Here's a comparison, the leave edges are clearly different, but the one on the left and right renders like that on 10 others machine with no problems, but the one in the middle is doing it like that on 1 particular machine.


Any thoughts!? In the zip file is a PSD for closer inspection, if anyone wants to take a look I'd be grateful!

Thanks,

-Johan

[Morbid Angel]

did you try updating bios? try on/off hyperthreading...see if any difference.

[johanboekhoven]

Hi Dmitry, thanks for replying!
We also did that, update and rollback, made no difference. My uneducated guess would be memory, but on the other hand that makes no sense at all...

Anyone got anymore ideas?

Thanks!

[tsvetan.geshev]

Hello,

You can try to check Windows regional settings for this machine, it should have the same settings and also opacity mode:

http://docs.chaosgroup.com/display/V...ymodeparameter

What material do you use for your plants and what type of texture. Which node do you use to load your textures - V-Ray HDRI node or bitmap node?

Double check, that the service pack versions are the same.

[johanboekhoven]

Tsvetan,

Thank you! I found indeed the setting on this machine is a comma and on the other machines a period. Test rendering now, will post the result here!
Again thanks!

-Johan

[johanboekhoven]

Unfortunatly, that was not the cause of the problem, although I had some hope for that suggestion. Next up, we'll be swapping out memory with another slave and see how that goes.
We use normal bitmap texture maps from max, not the hdr loader (yet).

As always open for other ideas and suggestions!

Thanks!
-Johan

[Morbid Angel]

Unfortunatly, that was not the cause of the problem, although I had some hope for that suggestion. Next up, we'll be swapping out memory with another slave and see how that goes.
We use normal bitmap texture maps from max, not the hdr loader (yet).

As always open for other ideas and suggestions!

Thanks!
-Johan

Just curious, if you take the opacity map and just render it on the place as self illuminated texture and compare between two machines if there is any difference in them at all?

[johanboekhoven]

Ok, had some time to investigate further. I duped the materials and meshes and replaced the bitmap loader with the VrayHDR loader, sRGB for the diffuse and straight alpha (1.0) for the alpha texture maps (plant materials). Now everything renders correctly.

So the plant material has
1. Diffuse PNG color map, 8bit sRGB
2. Opacity PNG map, 8 bit sRGB

Maybe it's PNG not properly being supported on that machine via the bitmap loader (I checked all service packs both windows and 3dsmax, all are equal).

So the obvious solution is to not ever use the max bitmap texture loader again, but that is not a real good solution for many reasons.
I will save the textures out to another format and test some more.

Still very much open for ideas!

Thanks,
-Johan

[Deflaminis]

If you turn off map filtering in the regular 3dsmax opacity texture, does it fix it?

[svetlozar.draganov]

This is most likely the same Autodesk bitmap-gamma-bug which is widely discussed into a few separate threads here.
Have you got an opportunity to test the scene with 3DSMax 2013?