Renders inconsistence across multiple machines

[BooKara]

Rending the same image with same settings on different machines and I'm noticing inconsistencies in the clouds.
One machine will make the clouds lighter especially in the shadows and the other will be darker.

Ideas?

Machines:
1)
•   Windows 10
•   64-Bit System
•   Processor: Intel i7-4820K CPU@ 3.70GHz
•   RAM 32.0 GB
2)
•   Windows 10
•   64-Bit System
•   Processor: Intel i7-6700K CPU@ 4.00GHz
•   RAM 32.0 GB

[yossam]

Are you using one monitor or two?

[archonforest]

If all settings are the same and using the same version (Like TG4 pro) on both machine and saving the end result the same way then it is pretty impossible IMHO.
Are u viewing the 2 picture on the same monitor?

[BooKara]

In the end I view both images on the same monitor and compare them in Photoshop as well.
This makes it difficult when I'm rendering a 360 frame animation on 5 different machines.   

Could the video card effect the way they are rendered?  Not sure if this would be the case if TG is CPU driven...correct?

Machine 1)  NVIDIA GeForce GTX 760
Machine 2) NVIDIA GeForce GTX 1070

[KyL]

What about the GI being computed differently? The best thing would be to use a GI cache to have the same illumination on both machine, or increase the GI samples by a fair amount

[BooKara]

Interesting thought. It would seem strange however if that were the case for people using multiple render nodes and trying to maintain consistency.

I'm going to run the same test on 2 machines that are exactly alike and see what happens. I'll update this thread when I get the results.

[Oshyan]

GI will have some slight differences between even successive renders on *the same machine*. This is because random numerical processes are part of the rendering process. You can address this in one or both of two ways. First, for non-animations, you can increase the consistency of GI by increasing the GI sample quality and cache detail. Second, for animations especially, you can (and absolutely should!) use GI Caches. You can render GI cache files across multiple machines then *use the same set of cache files for all renders*, and thus ensure consistency (because they are all referencing the same calculated GI solution). You can find out more about GI cache use in the documentation here:
http://planetside.co.uk/wiki/index.php?title=Terragen_3_Global_Illumination#Rendering_with_GI_cache_files

- Oshyan

[BooKara]

Thanks for the help Oshyan. I do use GI Caches when rendering animation but didn't think to use them on single frame renders. I'll give that a try.

[Oshyan]

If you need absolute consistency between renders on multiple machines, you'd need to use GI caches, whether in animation or not. I'm curious though what rendering you're doing on multiple machines of the same scene where you are seeing differences, but *not* in animation...

- Oshyan

[BooKara]

I'm doing render tests to show the time cost during production on different computers. (trying to push for a faster machine for iteration )  

[Oshyan]

Ahh, interesting. Well, higher GI settings, or GI caches, will give you consistency (caching will be the most consistent, of course).

- Oshyan