Corona 13 daily builds IR/viewport slowdown

[danio1011]

I have a really simple scene with basic materials (no textures used, only Corona basic materials), and my VRAM is almost full (7.4 GB out of a total of 8 GB is used). Even with this scene, using interactive is problematic and laggy. I have an RTX 3070, and my CPU is a Core i9 13900 with 64GB of RAM.
I never had this issue with previous Corona versions, even in much heavier files.

What Max version, just out of curiosity?

[danio1011]

Monitoring VRAM is good idea. I use 16+ GB VRAM GPUs but even then I still use only 1024px Viewport setting (remember CoronaBitmap uses the Environment setting, so just set 3x1024px and enjoy looking at blurry shit in viewport :- D !)

Have you tried either 3090 or 4090 for the 24gb memory?  I've been eyeing one of those as an upgrade from my 11gb 2080 ti.  The 3090 seems like a decent price point (~$1500 USD) considering the other factors besides VRAM don't impact performance that much...

[Sepia21]

I have a really simple scene with basic materials (no textures used, only Corona basic materials), and my VRAM is almost full (7.4 GB out of a total of 8 GB is used). Even with this scene, using interactive is problematic and laggy. I have an RTX 3070, and my CPU is a Core i9 13900 with 64GB of RAM.
I never had this issue with previous Corona versions, even in much heavier files.

What Max version, just out of curiosity?

I'm using max 2025.3, the most recent update

[Sepia21]

I did a test with a scene on my work PC (with an RTX 3070) and my home PC (with an RTX 3090). On the work PC, the Vram usage is 7.5 GB out of 8 GB and I will encounter a lot of slowdowns during interactive renders or even in material editor for a few seconds. On the home PC, the VRAM usage is 4.6 GB out of 24 GB and I don't encounter slowdowns. Both are on the latest version of 3ds Max and are using Corona's latest release. No other program is running in the background. I don't recall having issues like this using any of the previous versions of Corona and even on my home PC, 4.6 GB of VRAM usage for a scene that simple is a bit much. I will try to test the same scene on another PC running an older version of the Corona with an RTX 2070 Super and will report back.

[Aram Avetisyan]

I did a test with a scene on my work PC (with an RTX 3070) and my home PC (with an RTX 3090). On the work PC, the Vram usage is 7.5 GB out of 8 GB and I will encounter a lot of slowdowns during interactive renders or even in material editor for a few seconds. On the home PC, the VRAM usage is 4.6 GB out of 24 GB and I don't encounter slowdowns. Both are on the latest version of 3ds Max and are using Corona's latest release. No other program is running in the background. I don't recall having issues like this using any of the previous versions of Corona and even on my home PC, 4.6 GB of VRAM usage for a scene that simple is a bit much. I will try to test the same scene on another PC running an older version of the Corona with an RTX 2070 Super and will report back.

Can you please also check the GPU usage with IR, if any of the AI denoisers are enabled for IR? Check optionally with earlier versions (v12 hf1, v11 hf2 etc.) too.

For IR sluggishness in v12 update 1 - it may be due to slightly higher CPU than v12 hf1, so you should see higher speed (ray/s) stats for IR in v12 update 1 than in v12 hf1. If you can confirm this, I will appreciate it and it will help with troubleshooting too.

[danio1011]

I wonder if anyone experiencing this sluggishness has looked at their GPU VRAM usage in Task Manager?  That's when my viewport\slate\UI seems to come to a screeching halt for me lately.  Scenes that shouldn't really be maxing out VRAM still sometimes do.  Very odd.  Saying things are sluggish is an understatement, and when IR starts it can get nearly unusable.  Even in isolation mode with one object I still get 95% VRAM usage, although perhaps Max doesn't clear VRAM in isolation mode, can't say I've tested that before.

Windows 10
Max 2025
Corona 13 DB from July 30
Latest Forest Pack
RTX 2080 Ti driver 32.0.15.6094

If possible, please try with the latest stable release - Corona 12 update 1 - and let us know if you are still experiencing the sluggishness.
There is already a similar report being investigated.

Got a chance to test this yesterday.  Moving from the July 30 build to the stable Corona 12 Update 1 resulted in the same VRAM usage but did add an insane sluggishness to my UI\mouse that I hadn't experienced before.  Even with IR not running my mouse would freeze and pause.  Just running the cursor over complex objects in the viewport (not even selecting them) was enough to cause mouse lag.  Very odd.

I downgraded back to the July 30 DB and all that went away.  FWIW the scene I was in would result in a hard crash upon opening with the July 30 build after having been saved in Update 1.  I merged it into a new scene and that crash went away.

As for VRAM, Max 2025.3 seems to result in 3-4gb more VRAM usage than 2024 even with empty scenes.  I haven't tried it with Corona uninstalled fully but perhaps its a Max bug.  Sepia21 I'd be curious if 2024 gives you less VRAM usage like me *shrug*

[Sepia21]

I repeated the test on three PCs, and the results are as follows:

PC 1: Equipped with an RTX 2070 Super, running Corona 12 HF1 on Max 2025.3.
Opened Scene: Consumed 1.4 GB of VRAM.
Interactive Rendering: No change in VRAM consumption.

PC 2: Equipped with an RTX 3070, running Corona 12 Update 1 on Max 2025.3.
Opened Scene: Consumed 6.1 GB of VRAM.
Interactive Rendering: Increased VRAM usage to 6.5 GB.
After Stopping Interactive: VRAM usage rose further to 7.2 GB.

PC 3: Equipped with an RTX 3090, running Corona 12 Update 1 on Max 2025.3.
Opened Scene: Consumed 4.6 GB of VRAM.
Interactive Rendering: Reduced VRAM usage to 4.1 GB.
After Stopping Interactive: VRAM usage decreased further to 3.4 GB.

All PCs are running the same version of Windows 11 (24H2).

Regarding tests with Max 2024:
Unfortunately, I have Max 2024 installed only on PC 3 (RTX 3090), so I cannot replicate the test across all PCs. However, I noticed that Max 2024 consumes less VRAM compared to Max 2025. Running the same test on Max 2024 with the latest version and Corona 12 Update 1 resulted in:
Opened Scene: Consumed 2.4 GB of VRAM.
Interactive Rendering: No change in VRAM consumption during or after stopping interactive rendering.

[mienda]

I am experiencing exactly the same problems mentioned by Danio1011 using Corona v12 update 1 namely:
1) A slowness of the 3DSmax interface with a lack of fluidity.
2) This slowness appears especially during renderings (both in interactive rendering and production rendering..)... During renderings (production render) Windows becomes subject to slowness, internet browsing is jerky, everything becomes less fluid whereas with the previous version of Corona I had never encountered this kind of problem....
3) Like Danio1011 I noticed that if I save a file with Corona V12 update 1, it is impossible for me to open it with Corona 12 Hotfix 1 (and the "merge" also crashes)... Once Corona V12 Update 1 is reinstalled I can open these files again....

These slowdowns of the 3DSmax interface (2024 and 2025) under Corona 12 update 1 (especially during renderings) are extremely penalizing because all Windows is slowed down... Furthermore, by observing the task manager I observe that the processor, during renderings, to completely random power drops...
I specify that I work on a Threadripper 3990X station with 256 GB of ram and a 2080 Ti (latest drivers installed), under updated Windows 11.
Thank you very much for your attention.
Mienda

[Aram Avetisyan]

The sluggishness is known for high core machines and is being investigated.
Backward compatibility was never guaranteed - Corona 12 Update 1 saved scenes are not guaranteed to work with Corona 12 Hotfix 1, so please back up the scenes. Corona 12 Hotfix 1 saved scene should work fine with Corona 12 Update 1.

Please, whoever is investigating this: please check if IR is faster (more rays/s), for any given scene, in Corona 12 Update 1 than in Corona 12 Hotfix 1. If so, please confirm it, so we know that we are on the right track.

[danio1011]

The sluggishness is known for high core machines and is being investigated.
Backward compatibility was never guaranteed - Corona 12 Update 1 saved scenes are not guaranteed to work with Corona 12 Hotfix 1, so please back up the scenes. Corona 12 Hotfix 1 saved scene should work fine with Corona 12 Update 1.

Please, whoever is investigating this: please check if IR is faster (more rays/s), for any given scene, in Corona 12 Update 1 than in Corona 12 Hotfix 1. If so, please confirm it, so we know that we are on the right track.

Can you provide a link for V12 HF 1?  It's not listed under 'older versions' on the chaos download page and the changelog forum pages don't link directly to it that I can find.  Going to try rolling back from the July 30 build to see if my VRAM drops like Sepia's results.
 Thanks

[Aram Avetisyan]

The sluggishness is known for high core machines and is being investigated.
Backward compatibility was never guaranteed - Corona 12 Update 1 saved scenes are not guaranteed to work with Corona 12 Hotfix 1, so please back up the scenes. Corona 12 Hotfix 1 saved scene should work fine with Corona 12 Update 1.

Please, whoever is investigating this: please check if IR is faster (more rays/s), for any given scene, in Corona 12 Update 1 than in Corona 12 Hotfix 1. If so, please confirm it, so we know that we are on the right track.

Can you provide a link for V12 HF 1?  It's not listed under 'older versions' on the chaos download page and the changelog forum pages don't link directly to it that I can find.  Going to try rolling back from the July 30 build to see if my VRAM drops like Sepia's results.
 Thanks

I will try bumping this, so it appears in older download options in the website.

[mienda]

It seems that the backwards compatibility problem between Corona 12 hotfix 1 and corona 12 update 1 comes from the Corona camera because the scenes recorded in corona 12 update 1 crash all the time unless you don't merge the cameras (if you merge the scene without the cameras, it opens without problem...).
Finally, if the slowness problem on machines with many cores is a known problem, I had never encountered it before using Corona 12 Update 1....
Thank you for your attention

Mienda

[Aram Avetisyan]

Little update on this (responsiveness drop/slowdown with IR, v13 DBs, after some point, and v12 update 1):

We narrowed down the issue and have found one of the reasons of this, and it has been fixed internally.
There are some leftovers/cases where responsiveness drop can be observed and these are being handled as well.

[shortcirkuit]

great to hear! when can we expect a fix?  i assume it will be a hotfix?

Little update on this (responsiveness drop/slowdown with IR, v13 DBs, after some point, and v12 update 1):

We narrowed down the issue and have found one of the reasons of this, and it has been fixed internally.
There are some leftovers/cases where responsiveness drop can be observed and these are being handled as well.

[brr]

Little update on this (responsiveness drop/slowdown with IR, v13 DBs, after some point, and v12 update 1):

We narrowed down the issue and have found one of the reasons of this, and it has been fixed internally.
There are some leftovers/cases where responsiveness drop can be observed and these are being handled as well.

Hi,
The fast IR was always like the "heart" of Corona, and now it beats slowly. Are there any plans for HotFix for update 1?