Does interactive use GPU or CPU?

[Jpjapers]

Just got a new system and im noticing that despite the system being about 5x faster than my previous one the interactive window is cripplingly slow at times.
Potentially because i havent fitted the new GPU (currently have a basic 1gb one as a placeholder il the 1080 arrives) but im wondering if thatll even make a difference?

[maru]

Everything you do with Corona is CPU-based only - https://corona-renderer.com/features/proudly-cpu-based

GPU is used only for viewport in 3ds Max. Even the VFB and all post processing effects are done on the CPU.

If you are experiencing slow IR - please tell us what exact CPU you are using now, and what were you using before.

[Nejc Kilar]

Pretty much what Maru said + do keep in mind that if you are using UHD cache for the secondary bounces then in certain cases it will need a few seconds to calculate things even though you are using the IR. It does that when you have a tough lighting scenario.

That and or scene parsing (huge scenes) / displacement calculations, those can be a tad slow too :)

[TomG]

What are the CPUs in the old and the new system (and memory too)? Is it only IR that is slow, and regular renders are as expected? Is this all scenes, or just specific ones?

[Jpjapers]

What are the CPUs in the old and the new system (and memory too)? Is it only IR that is slow, and regular renders are as expected? Is this all scenes, or just specific ones?

Im noticing alot more noise on the new system in both interactive and standard render strangely but it could be the scene as its heavy.

Old CPU : Xeon E5-2643 @ 3.3Ghz
New CPU: AMD Threadripper 1950x

Old RAM 128GB
New RAM 64GB (Faster clock)

The benchmark ran in about a minute on the new system and in about 5 minutes on the old so i was expecting a vast speedup. As i say It could potentially be my scene as its quite heavy.
Is there a way to tell if a certain object or lightselect element is causing excessive noise?

[Jpjapers]

Ive figures out what was causing the issue. The lights i had set up infront of my strip light model to emit light were inside the perspex part of the model meaning i had a 90,000 sqft building lit through glass elements with thickness. Fixed it and the noise is cleaing up alot better now! However also good to note that the gpu wont add anything to the system speed.

[maru]

Also check if you don't have any 3ds Max photometric lights. They can dramatically slow down rendering on CPUs with many cores.

[Jpjapers]

Also check if you don't have any 3ds Max photometric lights. They can dramatically slow down rendering on CPUs with many cores.

No photometrics just corona lights and light materials.
Thanks for your help!

[ovidiumargan]

Hello all. I have kind of the same question. So if the interactive does work on CPU, why if i check the "Fast preview denoise during render" says "failed to initialize NVIDIA AI denoiser"?

My config is:

AMD Ryzen™ 9 3900X, 12-core
RAM 32GB
AMD ryzen 9 3900x

Point is that in interactive it doesn't denoise. Is there a way to use denoise without NVIDIA? Gets to the point in the image and kind of stops there.

[TomG]

Rendering is always CPU. Denoising CAN be GPU, with the NVIDIA AI Denoiser. This is fast enough that it CAN be used during interactive rendering. But yes, you do need a compatible NVIDIA card for it to work, either in interactive or final rendering. In all cases, the actual rendering remains pure CPU, and only the denoising step can be GPU.

EDIT - The NVIDIA denoising is the only one fast enough to use in Interactive Rendering.

You mention IR "stops there" - there is a limit you can set for how many passes IR will do (or you can set that to 0 for it to render forever). See https://coronarenderer.freshdesk.com/support/solutions/articles/5000520620-how-to-use-interactive-rendering-