Please note that this documentation space offers information for V-Ray 3.6! For most up-to-date documentation, refer to V-Ray Next for Modo help.

This page provides information on the V-Ray Denoiser post-process rollout of the V-Ray Main render settings.


Page Contents

 

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 (such as Beauty or RGB color) 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.

The V-Ray Denoiser has three preset options for its settings: Default, Mild, and Strong. Parameters can also be adjusted directly by selecting the Custom preset.

When rendering, the V-Ray Denoiser automatically adds a few render channels in the V-Ray frame buffer which are required by the denoising algorithm. Some of them are standard render elements such as Diffuse Filter. A few special render elements are also generated:

  • The noiseLevel channel is the amount of noise for a pixel as estimated by the V-Ray image sampler.
  • The defocusAmount channel is non-black when depth of field and motion blur are enabled, and contains the estimated pixel blurring in screen space.
  • The RGB color denoised channel contains the result of the noise removal.

 

The Denoiser can only work with the new variance-based adaptive sampling method introduced in V-Ray 3.30. Specifically, the Denoiser will not work with scenes where the Sampler Type for the Image Sampler is set to Adaptive Subdivision; only the Adaptive, Progressive, and Fixed rate methods will work with Denoiser. Additionally, when Sampler Type is set to Adaptive, the Adaptive method must be set to Default.

 


 

UI Path: ||V-Ray Main render settings|| > Denoiser post-process rollout

 

Parameters


 



Enable – Activates V-Ray Denoiser in Modo.

Render element name – The label for the channel generated by the denoiser.

Mode – Specifies how the results of V-Ray Denoiser will be saved.

Only generate render elements – All render elements required for denoising will be generated so that denoising can be done with the Standalone Denoise Tool. The information calculated within them will not be applied to other render elements, and no VRayDenoiser Render Element will be generated.
Hide the channel with the denoised result in VFB – The  RGB Color Render Element will be replaced with the denoised version, and the VRayDenoiser Render Element will not be present as a separate channel.
Show the channel with the denoised result in VFB.
Show the channel with the denoised result in VFB – The VRayDenoiser Render Element will be generated to contain a denoised version of the RGB Color Render Element using the specified settings. The original render elements, including the RGB Color Render Element, will not be changed.

Type – Specifies whether to denoise only the RGB color channel, or other render elements as well.

Single pass denoise on RGB only – Does a single pass at denoising on only the RGB Color channel, using other elements like the diffuse filter only to guide the denoising process. This method is better at cleaning up noise, but may loose small texture details or may blur too much areas of the image where multiple effects are visible at the same time (f.e. reflections and refractions through glass materials).
Denoise render elements separately – Denoises the lighting, global illumination, specular, reflection, refraction and atmosphere render elements separately and combines them into one denoised version of the RGB image. This method preserves texture details better, but with low settings may fail to clean up some types of noise. Note: This mode can only work correctly if no color mapping is applied to the render, so that the mentioned render elements add up correctly to the RGB image.

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

Default – Applies a mid-level denoising.
Mild – Applies a more subtle level of denoising than the Default preset.
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 will be. This parameter is available only when Preset is set to Custom.

Radius – Specifies the area around each pixel to be denoised. A smaller radius will affect a smaller range of pixels while a larger radius will affect a larger range, which will increase the noise removal. This parameter is available only when Preset is set to Custom.

Update... – Applies denoising on the image currently in the VFB. The image must have been previously rendered with denoising applied.

Use GPU acceleration – Uses the OpenCL version of the denoiser, if possible. It will fallback to the CPU version if OpenCL is not available.

Progressive Update Freq. – The regularity of updates during the progressive rendering. This value is roughly the percentage of the time denoising is allowed to take compared to total render time. A value of 0 disables updates during the progressive rendering, while larger values cause the denoiser to be updated more frequently. A value of 100 will cause updates as often as possible. Values ranging from 5 to 10 are usually sufficient.

Generate Render Elements – Specifies which render elements to add to the VFB automatically when rendering:

Manual – Adds only the noiseLevel and defocusAmount render elements; the rest must be added manually.
Depending on denoising type
 – Adds only the elements needed for the current denoiser type (single pass or by render elements). Single-pass denoising requires fewer render elements and choosing this option can save RAM and disk space, but it will not be possible to switch to per-element denoising.
All possible denoising elements
 – Adds all elements that could be required by the denoiser and allows switching between different types.


 




Example: Denoising Presets


The example below illustrates how Denoiser works using the presets. A purposely noisy render was set up using the Progressive Image Sampler with Max. render time in min set to only 3 minutes to leave plenty of noise in the render. To better see the noise level in each image, click the image to see it at full size.

 

 


RGB color prior to denoising


RGB color denoised (Mild preset)

 

 

 


RGB color denoised (Default preset)



RGB color denoised (Strong preset)

 

 

 


RGB color denoised 
(Custom preset: Strength = 5, Radius = 10)

 


RGB color denoised
(Custom preset: Strength = 10, Radius = 20)


 





Example: noiseLevel Render Element


The noiseLevel Render Element shows where areas of noise have been detected in the scene. White areas have the most noise, black areas have no noise, and gray areas have varying levels of noise.

 

 


RGB color prior to denoising

 


noiseLevel Render Element

 


RGB color denoised

 

 

 

Suggested Render Settings


  • While the denoiser can be quite effective at removing noise, it is not perfect; very noisy images can lead to artifacts and loss of image detail. For most scenes, use the Adaptive or Progressive image sampler with the Noise threshold set to 0.05 or lower. Additionally, the denoiser works best when the noise levels across the image are similar (the noiseLevel render channel is close to uniform grey), so using very low sampling is not recommended. 
  • When rendering animations with the Denoiser, disabling the Animated noise pattern option in the DMC Sampler parameters generally improves the results. 
  • Sometimes reflections/refractions can get very blurry from the Denoiser; this can be fixed by setting the Affect alpha and Affect Channels options to All channels in the V-Ray Material (as shown in image below), though this may slow down renders.


Adjust Affect alpha & Affect Channels to help with blurry reflections/refractions

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 for the rendered frame and does not consider the next and previous frame(s), 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.exr, anim_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:

  • Mode set to only generate render elements.
  • Render output set to vrimg or multichannel exr.

 

 

Notes


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

  • Textures or materials such as V-Ray Stochastic Flakes Material that could be considered to have a purposely noisy look will not be considered "noisy" by Denoiser, and will not be affected by the noise removal process.