How to use denoising in Corona for 3ds Max?

Updated July 19, 2024 08:54

You can use denoising in Corona to quickly make your images noise-free. Denoising significantly reduces render times by removing the need to wait until the noise refines during the rendering process.

There are 3 types of denoising in Corona:

Corona High Quality
NVIDIA GPU AI (fast preview)
Intel CPU/GPU AI (speed-quality hybrid)

Note: Starting from Corona 12, the new VFB 2.0 is the new default VFB in Corona, featuring an updated interface with improved user experience. For a complete overview, refer to the official documentation.

1. Corona High Quality Denoiser

This denoiser is a post-rendering effect which analyzes noise in the 3D space and smartly reduces it without producing splotches while maintaining sharp edges and texture details. It is not strictly a 2D post-process. The result can be interactively blended with the original non-denoised image directly in the VFB after the rendering is finished to achieve the desired level of denoising. This is especially useful if the denoised image appears to be over-processed (generally this should not happen but can sometimes be observed, for example in case of textures with very subtle patterns and rendering a small number of passes).

The main purpose of denoising, along with adaptivity, is reducing the number of passes needed to get a noise-free image. The reported render time reductions are between 50 and 70%. Denoising also attempts to remove fireflies (single bright pixels) from the image.

The Corona High Quality Denoiser is executed after the rendering is finished. This can be done by either limiting the rendering, or by manually stopping it after the desired time.

Note: Clicking "Cancel" in the 3ds Max rendering dialog will DISCARD denoising, and it will not be applied to the final rendering! To stop rendering and apply denoising, you need to use the "Stop" button in the Corona VFB or in the 3ds Max rendering dialog.

The Corona High Quality Denoiser has 3 modes:

High quality - full denoising
Only remove fireflies - useful in scenes where fireflies are the main issue, much faster than full denoising
Gather data for later - gathers denoising data for the standalone Corona Image Editor

There are two parameters controlling this denoising type:

Denoise amount - this blends between the denoised and non-denoised image. The default value of 0,65 provides good balance between denoising and fine detail.
Denoise radius - radius of the blurring filter. Increasing it may help reduce very strong noise. Decreasing can help prevent loss of fine details. The default value usually works best.

2. NVIDIA GPU AI Denoiser (fast preview)

This denoiser's main purpose, as the name suggests, is to provide fast, noise-free previews. It is applied almost in real-time during interactive or production rendering, and after the rendering is stopped. It requires a supported GPU to work (See: Hardware Requirements), which is detected during the installation.

NVIDIA GPU AI Denoiser works in a similar way to the Corona High Quality Denoiser, however there are some substantial differences:

It is preformed purely on the GPU (Corona High Quality Denoiser - on the CPU)
It uses machine learning ("AI") to smartly blur noise, but also to produce detail (Corona High Quality Denoiser cannot add detail to the image)
It can be used during interactive rendering too (Corona High Quality Denoiser can only be applied after the production rendering is finished)
It works almost in real-time and is applied to the image progressively as it renders (Corona High Quality Denoiser takes time and is applied only once, after the production rendering is finished)
It should be used mostly for interactive rendering, quick previews, and optionally for final stills (Corona High Quality Denoiser is designed to be used for high quality stills and animations)
It should not be used for animations, since it does not offer any kind of temporal consistency - rendering different frames will most likely result in flickering and artifacts (Corona High Quality Denoiser can be used for animations, provided that the base image quality is good enough)
NVIDIA GPU AI Denoiser, as opposed to the Corona High Quality Denoiser, does not feature any additional modes

The only setting available for this denoising type is Denoise Amount, which works exactly the same as for the Corona High Quality Denoiser – it blends the original non-denoised image with the denoised result, and this can be done interactively during rendering, or once rendering is finished.

The NVIDIA GPU AI Denoiser requires additional components to be installed during Corona installation. This is done automatically if a supported GPU is detected. In case of installation issues, the additional components can be installed manually.

See: How to install the NVIDIA GPU AI Denoiser in offline mode?

3. Intel CPU / GPU AI (speed-quality hybrid)

This denoiser combines the features of the Corona High Quality Denoiser and the NVIDIA GPU AI Denoiser. Since Corona 11, it can run on the CPU or the GPU (it does not have to be an Intel CPU or GPU though; it works fine with non-Intel hardware as well), and uses machine learning to produce noise-free results. It is slower than the NVIDIA GPU AI Denoiser (seconds vs milliseconds), but it can be applied to interactive rendering too (the Intel GPU denoiser only).

Denoising Limitations

There are some important things to bear in mind when using denoising:

1) Denoising can improve images which are noisy only to a certain degree. In case of extremely noisy images, denoising will not be able to help, and the result will be splotchy or full of artifacts.

2) Denoising requires additional render elements, which are invisible to the user. These render elements can take a considerable amount of memory, for example:

3dsmax.exe RAM usage for an interior scene rendered in 1920x1080 resolution with 10 denoised render elements:

No denoising – 6,5 GB
Fast Preview Denoising – 7,3 GB (+GPU VRAM)
High Quality Denoising – 7,3 GB

3) In Corona 11, the Intel AI denoiser is supported only by Windows-based systems and its GPU mode only works on NVIDIA GPUs.

Enabling Denoising

For Production rendering:

The mentioned 3 denoisers can be selected from
Render Setup > Scene > General Settings > Denoising > Mode:

For Interactive rendering:

Intel CPU / GPU AI or NVIDIA GPU AI denoisers can be selected from
Render Setup > Performance tab > Performance Settings > Interactive Rendering > Denoising during rendering:

Denoising Checkbox

You can switch between the raw before-denoising render and the denoised image, using a checkbox in the VFB and in the Corona Image Editor. This lets you switch denoising on and off so that you can easily compare the differences.

Denoising and Network Rendering

When using Corona’s distributed rendering:

All denoising types will be performed on the master machine only.
Denoising will not be performed on the render nodes at all, so they do not need to have supported GPUs or drivers installed for the AI denoising to work.

When using other types of network rendering (Autodesk Backburner, Thinkbox Deadline, Pulze Render Manager, etc) – sending jobs to render nodes so that each computer renders a different frame:

All types of denoising will be performed on all of the machines that are rendering.
Additional processing time will be needed for the High Quality denoising and supported GPUs and drivers must to be installed on all computers for the AI denoising to work.

Example Uses

1. Saving a CXR file and denoising it later

The "Gather data for later" option can be used to skip the actual denoising process, but save the denoising data within the CXR file. Such file can be denoised later using the Corona Image Editor.

Note:

Using the "Gather data for later" option will allow you to denoise an image later in the Corona Image Editor but only when using the Corona High Quality denoiser.
If you wish to denoise your image using the NVIDIA AI or Intel AI denoiser, choose either of those two, render your image, and save to CXR. You can then switch between these two denoising types in the Corona Image Editor.

2. Saving multiple versions of the rendering with different denoising amounts

Multiple "CShading_Beauty" render elements can be used to save different versions of the same image at once with various amounts of denoising applied. Individual denoising amount is specified in the properties of each CShading_Beauty element regardless of the setting in the VFB:

Multiple CShading_Beauty elements visible in the render elements list. The denoising value of each of the elements is different than the "denoise amount" currently set in Corona VFB. Click to enlarge.

3. Denoising other render elements

Denoising can be applied to other render elements too by enabling the "Apply denoising also to this render element" option in each element's settings.

Denoising Sum-Up

Corona High Quality Denoising
- Can be used for regular rendering only (Scene tab).
- Is performed on the CPU. If your CPU can run Corona, it can also run this denoising type.
- Is applied after the production rendering is stopped.
- Is more precise, and so requires more time to be calculated.
- Can be used for high quality stills and animations.
- Maximum allowed resolution of the denoised image and the number of denoised render elements are dependent on the available system RAM.
NVIDIA GPU AI Denoising
- Can be enabled for regular rendering (Scene tab) and for interactive rendering (Performance tab).
- Is performed on the GPU, which must be a supported NVIDIA GPU (See: Hardware Requirements)
- Is applied during rendering, almost real-time, and also when the rendering is finished.
- Can be used for extremely quick previews.
- Shouldn’t be used for animations (will almost certainly flicker).
- May be used for high quality stills (provided that the base image is of good enough quality and no denoising artifacts appear).
- Maximum allowed resolution of the denoised image and the number of denoised render elements are dependent on the available GPU RAM.
Intel CPU / GPU AI Denoising
- Can be used for regular rendering (Scene tab) and interactive rendering (the GPU mode only; Performance tab).
- Can be performed on either the CPU or the GPU. If your CPU can run Corona, it can also run this denoising type. Almost any GPU made in the past 10 years will run this denoiser too. Just make sure you have the latest drivers installed.
- Is applied during rendering, almost real-time, and also when the rendering is finished.
- Can be used for quick previews.
- Is much faster than Corona High Quality denoising, but slower than NVIDIA GPU AI denoising.
- Shouldn’t be used for animations (will almost certainly flicker).
- May be used for high quality stills (provided that the base image is of good enough quality and no denoising artifacts appear).
- Maximum allowed resolution of the denoised image and the number of denoised render elements are dependent on the available system RAM or the GPU RAM depending on the selected mode.