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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.

Images can also be denoised using the Standalone Denoise Tool included with the installation of V-Ray for Houdini.

The V-Ray Denoiser operates on other render elements (like RGB_Color) rather than being part of the rendering process itself, therefore the denoising operation does not require re-rendering of the scene.

There are three denoising engines to choose from - the Default V-Ray denoiser, the NVIDIA AI denoiser (V-Ray's implementation of NVIDIA's AI-based denoising algorithm), and the Intel Open Image Denoise.

When rendering, the V-Ray Denoiser automatically adds a few render channels in the V-Ray Frame Buffer which are required to guide the denoising algorithm. The two denoising engines require different render elements. Some of them are standard render channels like the diffuse filter color, the reflection filter color, etc. A few special channels are also generated for the Default V-Ray Denoiser:

• The effectsResult channel holds the result of the denoising operations and the lens effects that are executed over that image. The RGB Channel button in the VFB will toggle between the effectsResult and original RGB color channels.
• 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 Denoiserchannel contains the result of the noise removal. This channel appears in the VFB only if mode is set to Show denoiser result channel.

UI path: ||out Network|| > V-Ray Render Elements node > V-Ray > Render Channel > V-Ray Denoiser (RE)

Enabled – Enables V-Ray Denoiser.

Name – The text added to the end of the rendered file, when saved as a separate file (e.g. myrender.Denoiser.vrimg).

Engine – Allows choosing between the Default V-Ray denoiser, the NVIDIA AI denoiser, or Intel Open Image Denoise. Note that, the NVIDIA AI Denoiser requires an NVIDIA GPU. See the denoising engine examples below.

Hardware Acceleration – Uses the GPU device(s) to accelerate the denoising calculations. In case there is no compatible GPU device, denoising automatically falls back to use the CPU, even if the option is enabled. When the NVIDIA AI denoiser is used, this option is not available, as it requires an NVIDIA GPU.

Preset – When using the Default V-Ray Denoiser, use the presets to automatically set the Strength and Radius values.

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.

Mode – Specifies how the results of the Denoiser are saved.

Only Generate Render Elements – All render elements required for denoising are generated so that denoising can be done with the Standalone Denoise Tool. The information calculated within them is not applied to other render elements, and no V-Ray Denoiser Render Element is generated.
Hide Denoiser Element – The V-Ray Denoiser channel is not present separately in the VFB. The effectsResult channel is generated with the denoised image.
Show Denoiser Element – The V-Ray Denoiser Render Element is 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, are not changed.

Radius – Specifies the area around each pixel to be sampled for determining how to denoise a given pixel. Larger values produce smoother results, but slow down the denoiser.

Strength – Determines how strong the denoising operation is. Larger values remove noise more aggressively, but may blur the image too much.

NVIDIA AI Upscale –  When enabled, the rendered image is internally calculated with half the resolution set in the render setup (in each dimension), and the denoised image is upscaled to the full resolution using NVIDIA's AI upscaling technology. NVIDIA's AI upscaling technology represents an advanced method based on machine learning which provides better and more detailed results when compared to a standard image interpolation. For example, a 3840x2160 resolution renders the image internally in 1920x1080 and the AI upscaling denoiser produces the final 3840x2160 image from the lower resolution render.

Temporal Mode – Only available with the NVIDIA AI denoiser. When enabled, the Denoiser uses information from previous frames to create a smoother transition. Useful for rendering animation.

Panorama – Specifies that the denoised image can be wrapped around the left/right border. The denoiser can then use this information to avoid generating artifacts over the seamed area.

Denoise Alpha – Enabled by default. When disabled, the Аlpha channel remains undenoised.

Deep Output – Specifies whether to include this render element in deep images.