Slow rendering of high resolution images

[TomG]

Hi all!

Do we have (or need) a separate thread or Mantis report for the performance slowdowns anyplace?

I can confirm that on my system, as resolution increases, there are hits to the system performance, where the mouse pointer will slowdown etc. At 2K square I see none, at 4K it's slight, at 8K noticeable, at 16K very noticeable (and indeed the render just stopped before showing anything, leaving a black VFB).

It does seem related to the updating of the native picture viewer, if I have both open at the same time, whenever the picture viewer refresh gets to the bottom of the window, I experience the lag (lag happens even if the PV is closed, just leaving it open shows that it is related to it refreshing).


Thanks!
   Tom

[Rhodesy]

Yes that's it. Very noticeable at full res with lots of layers. But more of an issue when actually tone mapping and tweaking. Even more pronounced with bloom and glare changes. Why is the C4D vfb not just the same as the MAX one? Is it because it saves the settings back to the scene?

[TomG]

The Corona VFB would be the same, looks like the difference would be in copying the results back over to the C4D PV. I have no idea what the Corona VFB does with the Max native viewer, as I never ever open the native Max viewer at all :) But looking to me more like differences in the native viewers and the sync to them, rather than differences in the Corona VFB.

[Nejc Kilar]

Hi all!

Do we have (or need) a separate thread or Mantis report for the performance slowdowns anyplace?

I can confirm that on my system, as resolution increases, there are hits to the system performance, where the mouse pointer will slowdown etc. At 2K square I see none, at 4K it's slight, at 8K noticeable, at 16K very noticeable (and indeed the render just stopped before showing anything, leaving a black VFB).

It does seem related to the updating of the native picture viewer, if I have both open at the same time, whenever the picture viewer refresh gets to the bottom of the window, I experience the lag (lag happens even if the PV is closed, just leaving it open shows that it is related to it refreshing).


Thanks!
   Tom

www.dropbox.com/s/tp31fsy3hpupbs3/c4d%20corona%2C%20VFB%20suttering.mp4?dl=0

I've uploaded an example from my box. The cursor is fine but everything else isn't :)

Oddly, I get similar stuttering when I refresh / tweak certain materials. In that case the whole C4D stutters including the menus. The good thing though is that all of the threads are busy. I get way less stuttering if I limit the thread amount to like 36 and then render but as described in another thread... 36 and lower is the only value that works but thats like half of the threads available here.

I get stuttering (although usually less) when rendering a shader ball as well.

I tried the 3ds max version with the demo (demo max, demo Corona) and its way waaay more fluent :)

Not sure if thats helpful but hey... Can't hurt me posting.

[4b4]

One idea with the picture viewer / VFB slowdown that I can't test myself at the moment.

If you go edit > preferences > Corona and then go down to VFB settings you can change the default frame buffer and the update interval. I vaguely recall playing with this a few months back but stopped using it as forester didn't work well with the VFB only. Perhaps setting this to just the VFB and maybe decreasing the update frequency might speed things up on larger renders?

[TomG]

Changing Default frame buffer to Corona VFB, unchecking Show VFB render in PV, and unchecking Update PV image after rendering did not seem to change anything. However, raising the Update interval to the max 100 seconds did - there were still some stutters during scene parsing before rendering begins, and some after I stopped the render, but during the render no sign of the performance hits (well, most likely it would have had a stutter every 100 seconds, but I didn't leave it running to see :) )

[anton taf]

I still have issues with high resolutions.

I have this interior camera now. I try to render in 3500x resolution in two PCs. One Ryzen1700x, 32gb ram and one Dual xeon, 32gb ram.

With the Ryzen I got low memory errors and it crashed at 3500x. So I tried in lower resolution 2880x and it started fine (see image below).
With the xeon it started at 3500x after a lot of time Preparing. It used the disk a lot when preparing. It stopped using it for a while I think in the Passes 1 or 2. Now it is in Pass 4 and it goes slow. CPU utilization is lower than 100% with high use of the disk and memory.
Also the Rays/s Numbers are much lower when it uses the disk.

Let me know what you think. It's a bit strange for me, because this scene has very few plantation. It has many lights though...
Do you think 32gb RAM is very low for this kind of renders? Thanks

Notes for the screenshots:
The Ryzen is at 2880x resolution
The Dual Xeon is at 3500x resolution

[leo3d]

It's strange cause i already made more 6000px render and no crash (Sometime)
My feedback:
High and/or lot of displacements
Laubwerck instance

[anton taf]

Ok I think I found the issue.
I tried to delete as many unused objects from the scene as possible. And what I also turned off was some Planes with Portal material that I had at the openings. But in this scene my camera was actually outside of the Portal planes. I'm not sure, but I think this was the problem. So it was my mistake, sorry.
In the screenshot below you can see the Stats from the finished render at 3500x resolution

[anton taf]

I'm still having issues with the CPU performance while rendering. It is probably memory related, but sometimes it renders with CPU utilization 100% and some around 50% (very slow performance and render time)

Also I've noticed that when I have two scenes open, my main scene, and another one for render testing some elements from the main scene (copied), corona crashes when I switch back to the first scene to start render in high resolution. I need to fresh restart cinema in order to avoid crashing..

[anton taf]

This one (screenshot) was rendering for 19:59 hours in 3500x1867px and it stacked at about 5.35% noise (I had 4% limit in my settings). With low CPU utilization, high usage of the disk and ram.
I can't understand yet when it does it and when not... :/ 
(The main lighting of the scene was Corona sun and Sky)

Do you think it has something to do with the light instances? What do you suggest as best:
1. Corona lights only ?
2. Corona lights + Instances ?

[houska]

Hi Anton. Your findings are strange, indeed. In any case, remember that even the rendered image itself takes a lot of memory. For example your 3500px render has 50% more pixels than the 2880px one. This means that the framebuffer will take 50% more RAM. Also, the more passes you have in multipass, the more memory your framebuffer takes. You can do the math yourself - a 4-component pass (e.g. beauty) will typically take 16 bytes per pixel, which is about 100MB per pass in your 3500px render. With 20 such passes, you'll need 2GB of memory only for framebuffers...

[Nikola]

Hi Anton,

according to your screenshot https://forum.corona-renderer.com/index.php?action=dlattach;topic=16553.0;attach=65872 (committed and cached values) it really looks you don't have enough physical memory and system is heavily swapping. Would it be possible to send us the same screenshot for the lower resolution which renders fine (some 2880x as you wrote in the first post)? Thank you.

Nikola