Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: Rhodesy on 2021-07-29, 14:50:38

Title: Slow UHD Cache
Post by: Rhodesy on 2021-07-29, 14:50:38
Hello, I've got a big scene that eventually renders out fine and at full speed but the UHD cache and first pass or two only seem to work on one core and there is a lot of disk paging. I'm only using 55GB RAM out of 128GB and I'm not getting the virtualised RAM message either. So it seems Corona is prematurely looking ot page to disk. Any ideas why this would happen? I'm using corona 7.

Unfortuately interactive just crashes the scene so I have to render full frame to test and the UHD is taking 7mins which is a bit of a pain.

Also worth noting about this scene is that it can build right up to 80GB RAM usage when its first opened but then after a while it will eventually drop down to 20-30GB, so if I try to render straight away I get RAM warnings but if I wait half an hour the RAM dropsdown to more normal levels. Very weird. Wondering if its the slate editor hogging a lot of resources?

Thanks for any help anyway. 
Title: Re: Slow UHD Cache
Post by: TomG on 2021-07-29, 15:04:05
How does it work with the 4K cache, which is intended to be more accurate and use less memory?
Title: Re: Slow UHD Cache
Post by: Rhodesy on 2021-07-30, 11:22:53
Thanks Tom, doesnt seem to make much difference. I see the 4K Cache is still experimental rather than default, are there any draw backs from using it?

This is a very strange scene that takes different amounts of RAM on different machines. I have three machines here with 128gb each. One takes 73GB when rendering the other 109GB and the third wont render it. Bizzare. I tried rendering it with DR and the host machine couldnt render it but the node could so the node contributed all the passes which I was surprised about. Great work from Corona DR that it can handle that situation. Like I mentioned, it makes a difference how long the scene has been opened for. If its just opened the scene like backburner and DR does, that is when the RAM usage is highest. My workstation only took 73GB but the scene had been open on that for a while so the RAM usage dropped.
Title: Re: Slow UHD Cache
Post by: Avi on 2021-07-30, 13:20:36
are you using a lot of displacements in your scene with high value? Try rendering after turning off Global displacement from Render setup>Common>Displacement>TurnOff.

let me know the results.

Title: Re: Slow UHD Cache
Post by: Rhodesy on 2021-07-30, 16:30:47
Thanks Avi, there is a lot of displacement in the scene over several materials, but it doesnt seem to make much difference if its on or off. More RAM is consumed with it on as expected but the 4K Cache still only uses 1-2% CPU. Should this be a multithreaded process or is it just single threaded?

Also I notice for the first pass it gradually builds to 100% CPU until it gets to pass 2 where it keeps at 100% or there abouts. The RAM useage will also start to drop back down by 10GB or so. Bit of a mystery. Its also happened with other projects.

Cheers 
Title: Re: Slow UHD Cache
Post by: Avi on 2021-08-04, 09:56:59
Is it possible for you to send us your scene?

Please find the link to the uploader in my signature.

Looking forward to it.

Regards,
Avi
Title: Re: Slow UHD Cache
Post by: Zaborrad on 2021-09-03, 12:40:53
Hi guys,

I have same problem. With new Corona 7, I find out that in very complex and different scene it runs very slow. [at other scene it works perfectly]

I render with disable displacement. With Corona 6 is no such problem for this scene.
Title: Re: Slow UHD Cache
Post by: Avi on 2021-09-03, 13:13:26
Hi Zaborrad,

Before we start our investigation, please fill in this general survey form needed to troubleshoot your issue.

Link: https://docs.google.com/forms/d/e/1FAIpQLScO-6w4iP-MD3Drp-xsbu5SOL0NzxUOBuPoBTAEJdFMemKJlQ/viewform

Please also send us your scene for closer inspection of the problem. You can use our private uploader to send your scenes.

Link: https://corona-renderer.com/upload

Let me know once you have submitted the form & sent your scene for a closer inspection.

Looking forward to it.

Regards,
Avi