Gi cache creation problem again

[Hannes]

At the moment I am creating an animated version of my Rising image
https://planetside.co.uk/forums/index.php/topic,30257.0.html
I tweaked the scene and made a test animation. I saw there is a subtle GI flickering, so I thought about creating a set of GI cache files for the whole animation (200 frames).
I was rendering at 800 X 450 px. The rendertimes (no cache file created so far) started with seven minutes per frame and went up to almost half an hour due to a lot of cloud layers and some of them set to "receive shadows from surfaces". So far so good. So I set the Gi section to "Write GI cache file" after I changed the sequence step to 5 to only compute every 5th frame. After I hit the "Render sequence" button, I saw that creating the cloud GI caches took a very long time to compute. All in all it took more than six minutes to compute the GI cache for frame 1, and it got even longer with the following frames. As far as I know, there's no interpolation involved at this time? I stopped at frame 11 and decided to accept the subtle flickering.

Is this normal? The GI prepass takes about 15 seconds for the first frame before it starts to actually render with "automatic GI cache file (no file)" checked, but calculating the same (I presume) GI cache for saving takes six minutes, whereas the complete render process without precalculating a file doesn't take longer?

[Matt]

If you enable caching of "Cloud v3, Easy Cloud" when writing GI cache files, the time required for this can be higher than other cache data. Unlike "Surface points" and "Atmo, Cloud v2" cache data, the Cloud v3 and Easy Cloud caches are normally calculated on the fly during the final pass, but when you cache them into a file it has to do this in the prepass instead.

If it's taking too long, try reducing "Cloud GI quality". Even the "Low" setting might be sufficient because the caching will eliminate flicker. "Cloud GI max ray depth" also affects how long the cache generation takes. You can also reduce the "Ray-marching quality" on the cloud layer's Quality tab; this can be different from your final pass.

[Hannes]

Thanks a lot, Matt!

[Hannes]

I played with the settings and could reduce the calculation time at least from 6 minutes to 3 to 4 minutes per frame. Thanks again!

[Hannes]

I just stopped it and disabled the calculation for "Cloud v3, easy cloud" and it takes only a few seconds per frame. There is only one V3 cloud in the distance and in my animation I see the flickering only on the boat, so I hope, it will be enough.