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# Denoiser

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## Overview

The V-Ray Denoiser takes an existing render and applies a denoising operation to it after the image is completely rendered out via normal means. The denoising operation detects areas where noise is present and smooths them out.

Because the V-Ray Denoiser operates on other render elements rather than being part of the rendering process itself, the denoising operation does not require rerendering of the scene. The Denoiser settings can be quickly changed and tested over and over to improve the result.

Although V-Ray Denoiser is a render channel, for ease of access it is directly positioned under a separate rollout in the Settings tab. Don't search for the Denoiser in the Render Elements list. Just enable it from the Render rollout and if needed adjust its settings from the Advanced panel.

Currently the scene can contain only one Denoiser preset. Future versions of V-Ray will support simultaneously multiple Denoiser channels with different settings.

Original
Denoised

## UI Path

||V-Ray Asset Editor|| > Settings > Denoiser

## Denoising Engines

VRayDenoiser offers a choice between the Default V-Ray denoiser and the NVIDIA AI denoiser. Each offers a different denoising algorithm that comes with different benefits.

Default V-Ray denoiser - V-Ray's denoising algorithm. It can utilize the CPU or the GPU (AMD or NVIDIA GPUs) to perform the denoising. It is consistent when denoising render elements, as it applies the same denoising operator to all render channels. This means that it is recommended for denoising the render elements to be used for compositing back the beauty image. In addition, it comes with a Denoiser Tool, which is recommended for denoising animation by using frame blending.

NVIDIA AI denoiser - V-Ray's integration of NVIDIA's AI-based denoising algorithm. The NVIDIA AI denoiser requires an NVIDIA GPU to work, regardless of whether the actual rendering was performed on the CPU or GPU. This means that rendering on the CPU will still require an NVIDIA GPU for denoising with the NVIDIA AI denoiser and has some advantages and drawbacks compared to the Default V-Ray Denoiser. For example, the NVIDIA AI denoiser performs the denoising faster, but is not consistent when denoising render elements. This means that there will be differences between the original RGB image and the one reconstructed from render elements that are denoised with the NVIDIA AI denoiser. It also doesn't support cross-frame denoising and will likely produce flickering when used in animation.

The Nvidia AI denoiser only works on Nvidia GPUs starting with the Kepler GPU architecture (GTX 6xx series and newer).

## Parameters

Enable – Turns the Denoiser on or off. When enabled, it automatically adds the Denoiser as a Render Element.

EngineAllows choosing between the Default V-Ray denoiser and the NVIDIA AI denoiser.

Preset – Offers presets to automatically set the strength and radius values. For more information, see the Denoising Presets example below.

Mild – Applies a more subtle level of denoising than the Default preset.
Default
– Applies a mid-level denoising.
Strong – Applies a stronger level of denoising than the Default preset.
Custom – Allows the strength and radius parameters to be set to custom values.

Strength – Determines how strong the denoising operation is.

Radius – Specifies the area around each pixel to be denoised. A smaller radius affects a smaller range of pixels. A larger radius affects a larger range, which increases the noise removal.

Mode – Specifies how the results of the Denoiser are saved and presented in the VFB.

Only Render Elements – All render elements required for denoising are generated but a denoised version of the image is not computed. VRayDenoiser and effectsResult render channels are not generated. Use this option if you plan to denoise a sequence of images using the standalone denoising tool and do not want to spend time on denoising during the actual rendering process.
Hide Denoiser Channel – The VRayDenoiser channel is not present separately in the VFB. The effectsResult channel is generated with the denoised image.
Show Denoiser Channel – The VRayDenoiser and effectsResult channels are generated.

Update button – Press to regenerate the denoiser channel without having to re-render the scene.

Update Frequency – Controls the regularity of denoiser and lens effects updates during progressive rendering. Roughly this specifies the percentage of the total render time that is allotted to the effects evaluation. Larger values cause the effect to be updated more frequently. A value of 100 causes updates as often as possible. A value of 0 disabled the updates during progressive rendering. Effects are applied after the rendering process is finished and are not applied if the rendering process is canceled.

### Example: Denoising Presets

The example below illustrates how VRayDenoiser works using the presets. A purposely noisy render was set up using the Progressive Image Sampler Type with Render Time set to only 3 minutes to leave plenty of noise in the render.

RGB Color Render Element prior to denoising

V-Ray Denoiser (Mild Preset)

V-Ray Denoiser (Default Preset)

V-Ray Denoiser (Strong Preset)

V-Ray Denoiser (Custom Preset: strength: 5, radius: 10)

V-Ray Denoiser (Custom Preset: strength:10, radius: 20)

## Denoising Animations

When denoising animations, it is recommended to use the Standalone Denoiser Tool. Unlike the denoiser integrated in the UI, the standalone tool can do frame blending for animations, which reduces flickering. The integrated denoiser only works on the rendered frame and does not take the next and previous frame(s) into account, like the standalone tool does.

To denoise an image sequence with vdenoise run the following command:

vdenoise -inputFile="path\to\sequence_????.ext

where the question mark (?) replaces the digits in the sequence's file names.

For example, if the images in the sequence are named anim_0001.exranim_0002.exr, etc. and are located in the folder c:\renderoutput, the full command will be:

vdenoise -inputFile="c:\renderoutput\anim_????.exr

When that command is run, the sequence is read and for each frame, the specified number of adjacent frames are also considered. A new output image is then written for each frame.

### Recommended settings:

• Мode set to only generate render elements.
• denoising engine set to Default V-Ray denoiser.
• Render output set to vrimg or multichannel exr.

The NVIDIA AI denoiser does not perform frame blending and will likely produce flickering when denoising animations.

## Notes

• Image denoising takes place after the frame has been rendered and will not show up until all rendering has finished.

• Textures or materials that have a purposely noisy look will not be considered "noisy" by the Denoiser. They will not be affected by the noise removal process.