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default cache question.

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default cache question.

PostSat Jun 27, 2020 1:23 am

I'm not a fusion operator, but I'm getting somehow the feet wet. so please, bear with me. (you're allowed to RTFM me!!)

my questions are:
1) why the DiskCaches path in fusion is not the one we setup in resolve setting [working folder] - [cache files location] as default? it will be logical to me that it should be that and not the OS drive, we setup one place with a plenty fast drive and everything should be there.

2) once I set that manually and change the project, i have to set that again if i want to be in another place. if that follow the resolve setting it could be avoided.

3) if i have two boxes, if I set the cache on box 1 to [SAN/place/cache], and I open the project in box 2, will it use that path or whatever is the default in that box?

4) where i tell Fusion which cache clip format it uses?

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Bryan Ray

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Re: default cache question.

PostSat Jun 27, 2020 2:45 pm

The broad answer is because Fusion is not 'native' to Resolve. It was crammed in with a crowbar and some grease, and it's not truly fully integrated yet. So the Fusion settings are in a completely different place than the rest of Resolve's settings.

I don't have the ability to test the behavior of the path maps on multiple workstations, but changing one, then switching projects doesn't reset them, so I am guessing that they're stored in the Resolve installation, not in the project. You'll therefore probably have to set the path on each computer where you use Resolve.

As a compositor, Fusion has different assumptions than the rest of Resolve about what is needed in a cache. Compositing requires an artist to be able to see every single pixel on every single frame. The cache is therefore optimized for accuracy rather than performance, so it is not compressed. The file format is therefore always a sequence of Fusion raw files.

I'm not at all familiar with the caching mechanism that occurs between Fusion and Resolve. It's my understanding that the MediaOut is supposed to be somehow cached to a video format that will play back smoothly on the timeline. But I don't know a thing about that.
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Re: default cache question.

PostTue Jun 30, 2020 9:08 am

The Resolve "Render Cache" is described starting page 205, in "Chapter 6: Improving Performance, Proxies, and the Render Cache". It's the same one used by Color, so you're probably already familiar with it.

As Bryan says, it's quite separate from Fusion's own "Disk Cache". Personally I haven't used the Fusion Disk Cache at all yet, because when I tried it it seemed to require rendering out the entire composition for the given nodes, which didn't suit my workflow.

I've found the Render Cache somewhat useful for Fusion-in-Resolve work.

In brief:
A. You choose the format in Project Settings -> Master Settings.
B. Options include Uncompressed, ProRes and DNxHR.
C. There's no option for reducing resolution, I believe it always caches at full resolution. But you can choose a lower quality to save disk space at least (not sure if it saves much render time)
D. There are three Render Cache options: None, Smart and User. Their various permutations are a bit involved, so read page 209 for full details, but generally choose User if you want more control over what is cached. This is also affected by some tickboxes in the same area of Master Settings, which decide when background caching occurs (default: after 5 seconds of idle), whether all Fusion effects are automatically cached, and also have options for caching Edit page compositing and transitions.

On top of that there's Proxy -> Off/Half/Quarter. This only seems to affect live playback, both on Edit and Fusion pages. I've found this useful for live playback on the Fusion page, where dropping to Quarter will increase the FPS of my current comp from 4 to around 10. I guess this is roughly analogous to Fusion Studio's Proxy setting, except with only the "2" and "4" options.

In the project I'm working on, I have resource-intensive 3D Fusion effects for 100% of my runtime. If I want to do live playback I can get 10 FPS if I drop to Quarter, but that's still not fast enough to get a decent feel for animations and the like. Plus I can't hear sound on the Fusion page (not that it would sound great at 10 FPS anyway).

As a result, I've been using the following caching strategy:
1. Render Cache format set to ProRes 422 HQ
2. Render Cache mode set to User
3. "Automatically cache Fusion Effects in User mode" : No
4. "Enable background caching after" : 2 seconds
5. On the Edit page, I have "Bypass Fusion & Grades" on most of the time, so I see no Fusion output in the viewer. This enables me to scrub very fast through footage. I have a shortcut assigned to this toggle so I can quickly switch between on and off when I do want to see the Fusion output of a given frame or section from Edit.
6. When I need to see the Fusion output for a section, eg to check my camera moves are OK and lined up with audio, I use the Edit page razor to cut out a small clip that contains the area I want to see.
7. Then on that clip I choose Render Cache Fusion Output -> On. This gives me the red bar at the top of the timeline, and I sit and wait for it to turn blue. Once it's blue I can disable "Bypass Fusion & Grades", and can now watch the cached section at 30 FPS with full Fusion output.
8. Once I'm happy that the section is OK, I usually then remove the cuts (Delete Through Edit) so I don't have more clips than I need, and set Render Cache Fusion Output -> Off again so I don't end up caching material I don't need for now. Then I usually re-enable Bypass Fusion to get back to fast scrubbing. I sometimes toggle this off on the Edit page to check individual Fusion frames.

An example of how I cache: I want to see the Fusion effects across the boundary of these two clips, so I have cut out a small section from each, and set Render Cache Fusion Output to On for both. The red bar appeared above them, and is now turning blue as it caches.

This is working reasonably OK for me, though it's definitely not ideal and I wish there was a way on Edit to choose an arbitrary range for caching, so I didn't have to keep cutting sections out of clips to cache them.

One thing I should add is that at least on my system, I have been unable to get reliable caching within Resolve's Fusion page. When I hit play I see the green bar on the Fusion timeline, but it seems unable to cache more than 2-3 seconds at once. After it reaches a certain length, the green bar starts moving along the timeline rather than continually expanding.

This is probably because my 48GB RAM is not enough for Resolve + Fusion with the comp I have, especially as Resolve's settings won't let me allocate more than 36GB in total to Resolve, which limits Fusion to 27GB.

This limitation has made me much more reliant on Resolve's Render Cache, which caches to disk and therefore can cache any duration. Plus I usually want to hear the audio at the same time anyway.

A final point to note: I have found some unreliability with the Render Cache in terms of when it will start caching. As mentioned I am in User mode and am setting individual clips to Render Cache Fusion Output = on. The expected result is that as soon as I do that, I see the red bar at the top, and then within 2 seconds that bar starts turning blue (because my Background Caching setting = 2 seconds).

However, sometimes the red bar appears but never starts turning blue, no matter how long I sit idle waiting. Other times, less frequently, the red bar doesn't appear at all.

In both these situations I have to:
1. Turn the current clip's Render Cache Fusion Output to Off
2. Set Render Cache to None
3. Set Render Cache back to User
4. Set the current clip's Render Cache Fusion Output to On again

This usually fixes it. If I try doing only steps 2 & 3 it sometimes fixes it, but not always, hence I now always do all four steps. Annoying!
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Sam Steti

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Re: default cache question.

PostTue Jun 30, 2020 10:02 am

Hey Walter,

Hope you're ok, it's been a while now ;) ...

So, I'm personally wet up to my chest with Fusion, when "only my feet were", I decided years ago to opt for another solution, for Bryan's explanations reasons.
I know you probably won't do the same but but the Fusion Connect way I opted in not only solved this but global stability too. But yes, moving with 2 pieces of software is not so handy, I know...

That said, I don't remember I had you n°2 issue, I will check and no, as Bryan wrote, about your point n°4 you cache in full res in Fusion : this is also why I answer here, I wondered yesterday (!) wether Fu would take optimized media to work with if I made some, or native ones (in both Fusion inside Resolve and Fusion standalone by the connect way)...
Also will fusion cache in native codec res even if it works with optimized media ?

To be continued... ;)
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