Rendering with Light Cache "From File" is many times longer

[f2b]

Hello,
I'm experimenting tile render with VRay 6. With VRay 3.7 i was used to save light cache for the whole frame (it was the task of one block in the render Job in the render farm), and then i load Light Cache from this file, to render each tiles. Rendering light cache once, avoid "GI seams" between each tiles...

But in VRay 6 it appears that when i load Light Cache from file, tiles takes 4 times longer to render one tile! ( 666px x 374px, 2min 40sec when rendering directly, and 12min 56sec if i render with LC from file)

It's pretty surprising that loading light cache from file can multiply so much render time for a tile. It can takes some seconds to load this 20Mo file, and i should save time beacause it does not re-render it. So time balance shoud be null (more or less few seconds...)

Could you investigate on it please? Does Light cache file save every informations, even when using light cache for glossy rays?

[viktor_angelov]

Hi f2b Thank you for sharing with us!

There are couple of things to be discussed:
1. Where is the scene file saved? Is it Network located? Hard Disk? SSD?
2. Does it happen with every scene?
3. Does it occur if you are using Brute Force?
4. Are you using Irradiance map in V-Ray 3.7 or Light Cache?
5. Does it happen on other machines, too? Or just one computer?
6. Could you please share the scene you are using to reproduce the issue so we can observe it on our side as well?
- You can do this here or by submitting a request to our system: Submit a request
7. How do you render? Do you use Deadline or any other third party rendering software?

[f2b]

Hi Viktor!

1. C4D Scene + LC file are located on network, scene size is 1Go
2. Yes it's also happen with simplest scene (see attachement)
3. I'm not sure i understand, but when i use BF + BF (and not BF+LC), i have no problem, because no GI is cached to file
4. In 3.7 i was using BF + LC for every perspective images, and then rendered with Tile rendering method
5. It happen on every machines
6. Test scene uploads in attachement
7. I use only CGRU, but i can easilly reproduce manually. For example i subdivide my full frame in 9 tiles (3 subdivs so). In my scene i duplicated the main camera to render the top left tile. So camera settings become Focal length *3 , Offset X -100%, Offset Y -100% and for render setting Width and Height resolution divided by 3...

[boyan]

Hello, f2b,

Thank you for the report and response. Could you please let us know if you see improvement of render time when you render it without DR, only on your local machine?

Cheers,

[f2b]

hmm, but i don't use Distributed Rendering. Tile Rendering is a very basic process, not linked to VRay or C4D.
The test i reported in my last post was rendered "manually" (no scripts involved...), on my local worstation. And it allows to figure out that rendering a tile (basically the top left region for this example) of the original full frame image, render time is multiplied by 4 when using LC from file.

I can't find any explanation for now