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Denoising - Arnold for Houdini

Further Reading
See also Denoising in the Arnold User Guide

There are three denoising options available for rendering with Arnold:

OptiX™ Denoiser imager

This imager is available as a post-processing effect. The imager also exposes additional controls for clamping and blending the result. It is based on Nvidia AI technology and is integrated into Arnold for use with IPR and look dev. The OptiX™ denoiser is meant to be used during IPR (so that you get a very quickly denoised image as you're moving the camera and making other adjustments).

Oidn Denoiser imager

The OIDN denoiser (based on Intel's Open Image Denoise technology) is available as a post-processing effect. It is integrated into Arnold for use with IPR as an imager (so that you get a very quickly denoised image as you're moving the camera and making other adjustments).

Arnold Denoiser (Noice)

The Arnold Denoiser (Noice) can also be run from a dedicated UI, exposed in the Arnold Denoiser or as an imager. To use the Arnold denoiser, you will need to render images out first via the Arnold EXR driver with variance AOVs enabled. It is also available as a stand-alone program (noice.exe).

This imager is available as a post-processing effect. You can automatically denoise images every time you render a scene, edit the denoising settings and see the resulting image directly in the render view. It favors quality over speed and is, therefore, more suitable for high-quality final frame denoising and animation sequences.

An example scene file can be found here.

Note:

imager_denoiser_noice does not support temporal denoising (required for denoising an animation). Use the Arnold Denoiser imager when rendering a single frame.

The Arnold Denoiser is a stand-alone program post-process denoiser executable. It works on EXR files with multiple layers (merged) and outputs an EXR file with the denoised layers. It takes into account multiple frames and multiple light AOVs. Like most denoisers, it considers a neighborhood around the current pixel and looks for similar neighborhoods inside a given search area to blend together. To use the Arnold Denoiser, you will need to render images via the Arnold EXR driver.

Note:

Noice can work with the gaussian_filter or box_filter and sets up any additional filters it may need. A denoising tutorial can be found here.

The Output Variance AOV toggle on the Arnold ROP needs to be selected to generate the AOVs that the denoiser requires.

Arnold Denoiser ROP (left). Output Variance AOV toggle in Arnold ROP (right).

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