UHD Cache settings for animation?

[bograt]

Hi,
I have a animation to render and wondered if someone could give me advise on the best uhd cache settings?
The shot is fairly simple, it's just a camera moving down a corridor with white walls either side, and a glossy concrete floor. The shot is about 200 frames long.
What would be the best approach for the HD Cache? Should I be using load and try to append? If so how would I go about this? Am I right in thinking I would render out 10th or 20th with settings: calulate from scratch - save to file, then render out every frame using settings: try to load and append - save to file?
I'm still a little confused about how try to load and append actually differs to load from file.
Thanks

Jules

[bograt]

I just wanted to add that I have read the UHD Cache info page but don't fully understand it.

[maru]

If there are no moving objects or lights in this scene, the best and fastest way would be to switch preset to "Animation (flicker-free)", go to some frame in the middle of your animation (it's not so important, doing this for the first frame should work fine too), set precomputation to "calculate from scratch", set "after render" to "save to file", hit render, wait for the cache to calculate, cancel rendering, switch "computation" to "load from file". That's all. You do not need to repeat this process. I believe everything is described pretty straightforward here https://coronarenderer.freshdesk.com/support/solutions/articles/5000515648 , I hope this is the "UHD info page" that you are referring to.

[juang3d]

IMHO if you don't want any headache change things to animation settings and leave it as it is configured, if you want rise a bit the quality spinner from 1.0 to 1.5 but this is not necessary if you don't have anything super complex, and forget about precalc because in the end you will be saving 1 minute per frame or 2, from 15 minutes or 30 minutes per frame for the complete render, so you won't gain too much and you will loose more time preparing and doing everything.

UHD Cache works great in animation mode as is :)

Cheers.

[bograt]

Thanks for the advice. Yes that was the page I was referring to. The scene I was working on had some dark corners which would have required many indirect bounces to illuminate, even with precision set at 3 there was pretty bad flickering (not noise). In the end I added some other lights and the flickering cleared up.
I can see the documentation is fairly clear but I just struggled to understand exactly what 'load and try to append' was actually doing and when it should be used. If the cache is 'appended' each time what benefit do you gain over calculating from scratch each time?
If during the animation a new area is exposed (e.g moving passing a doorway into another room), would the single pre-loaded cache not fail to calculate the lighting in that area?
I would normally just run several tests but in these circumstances it can be extremely time consuming, and doesn't necessarily improve my understanding of the processes that determine the result.
Thanks again.

[maru]

I was working on had some dark corners which would have required many indirect bounces to illuminate, even with precision set at 3 there was pretty bad flickering (not noise). In the end I added some other lights and the flickering cleared up.

Were you using the "animation flicker free" preset? If so, then this should be reported as a bug. It would be best if you could provide us with the scene or a simplified version of it where this problem appears. Were you by any chance using Corona lights with .hdr textures plugged in?

I can see the documentation is fairly clear but I just struggled to understand exactly what 'load and try to append' was actually doing and when it should be used. If the cache is 'appended' each time what benefit do you gain over calculating from scratch each time?

If you calculate from scratch for each frame - the cache may be slightly different for each frame and nothing bad will be visible in stills, but there may be some flickering when comparing frames in animation. No flickering should occur when using "animation flicker free" preset, but calculating new cache per frame will add much render time for you, especially if there are many frames in the animation and if the scene is complex.
When using the "append" option, the slightly different cache files will be merged together to produce a more smooth result.

If during the animation a new area is exposed (e.g moving passing a doorway into another room), would the single pre-loaded cache not fail to calculate the lighting in that area?

There should be no problem as the cache is calculated for the whole scene and is not view-dependent. (I will consult this with Ondra just to make sure)

[bograt]

Thanks, I'm much clearer on that now. I'll try to upload a simplified scene where the flickering is present when I have a few minutes spare.

[maru]

Update: the cache is view-dependent in a way so if you are moving through a huge scene with different rooms there may be little problems (unfortunately this simply requires checking). The best solution for such case would be to use load+append option and render every Nth frame (20? 50?) with time limit set to 1s to calculate UHD cache only. Then use the generated cache for the final rendering.