This page provides information on the V-Ray denoising tool available on all platforms.


Page Contents


Overview


The V-Ray installation includes a standalone denoising tool called vdenoise that can be used to denoise still images or animations outside of Maya. This is especially useful for animations because the standalone tool can look at multiple frames at once and produce a better denoising result. The vdenoise tool works with either .vrimg or multichannel OpenEXR files and writes out files with the same format. 

 

Installation


The vdenoise tool is a part of the V-Ray for Maya installation. You can quickly open a command prompt in the folder where the vdenoise tool is located.

On Windows, the vdenoise.exe is located in C:\Program Files\Chaos Group\V-Ray\Maya 2016.5 for x64\bin. You can also start it from Start Menu > Programs > Chaos Group > V-Ray for Maya > Tools > Denoiser tool.

On Linux, the vdenoise executable is located in /usr/ChaosGroup/V-Ray/Mayannnn-x64/bin where nnnn is the Maya version.

On Mac OS X, the vdenoise executable is located in /Applications/ChaosGroup/V-Ray/Mayannnn/bin/ where nnnn is the Maya version.

 

Generating the Needed Render Elements


The denoiser needs several render elements in order to work optimally. The easiest way to generate these render elements is to add the VRayDenoiser Render Element to your Maya scene.

 

Required Render Elements


The required render elements are listed below. Add the VRayDenoiser or Denoiser Render Element to your scene to generate the necessary render elements automatically.The standalone denoiser will still run when some or all of these render elements are missing, but results might be too blurry.

For single pass RGB denoising:

  • Noise level (named noiseLevel) - The denoiser relies heavily on this render element to provide information used during the denoising operation.
  • Defocus amount (named defocusAmount)
  • World positions (named worldPositions or wpp)
  • World normals with bump mapping (named worldNormals)
  • Diffuse filter (named diffuseFilter or VRayDiffuseFilter)
  • Reflection filter (named reflectionFilter or VRayReflectionFilter)
  • Refraction filter (named refractionFilter or VRayRefractionFilter)

 

Additional render elements for multipass per-render elements denoising:

  • Atmosphere (named atmosphere or VRayAtmosphere)
  • Background (named background or VRayBackground)
  • Global Illumination (named globalIllumination or VRayGlobalIllumination)
  • Lighting (named lighting or VRayLighting)
  • Reflection (named reflection or VRayReflection)
  • Refraction (named refraction or VRayRefraction)
  • Specular (named specular or VRaySpecular)

 

Denoising Still Images


To denoise a single .vrimg or .exr image, use the following format for the command:

vdenoise -inputFile="path\to\image.ext"

where path\to\image.ext is the path and file name of the .vrimg or .exr file that you want to denoise.

For example, if the file you want to denoise is called render.exr and is located in the folder c:\renderoutput, the full command will be

vdenoise -inputFile="c:\renderoutput\render.exr"

 

Denoising Animations


To denoise a sequence of images, you must have all frames already rendered, as the denoiser needs to look at several frames at the same time. Use the following format for the 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"

Denoiser Options


You can control the denoiser through optional switches on the command line. To list all available options in the command prompt window, run the denoiser without any arguments (vdenoise command) or use the -help switch:

vdenoise -help

The table below shows the optional switches, which are also displayed by the vdenoise -help command. To use a switch, precede the switch with a hyphen (-) and follow it with an equals sign (=) and the desired parameter, as shown in the table.

 

SwitchDescription
-inputFile="<fileName.ext>"

Specifies the input . vrimg or .exr file. Can contain paths and wildcards such as a question mark (?) to indicate digits in file names. Examples:

vdenoise -inputFile="c:\renderoutput\render.exr" - Denoise a single image named render.exr located in the c:\renderoutput folder.
vdenoise -inputFile="c:\renderoutput\anim_????.exr" - Denoise a sequence of frames in the c:\renderoutput folder named anim_0001.exr , anim_0002.exr , etc. 

Note that in order to denoise a sequence of images you must have all frames already rendered, as the denoiser needs to look at several frames at the same time.

-mode=strong|default|mildSets one of three predefined presets for the radius/threshold/noise level multiplier.
-elements=0|1Specifies the method for denoising render elements.
0 - Colors in the final image are denoised in one pass. (default)
1 - Render elements are denoised separately and then composited together.
-boost=0|1|2

Boosts the effect of the selected preset.
0 - No boost. (default)
1 - Moderate boost.
2 - Large boost.

-skipExisting=0|1 Determines the file-processing behavior when a corresponding output image already exists.
0 - Do not skip: The input image is processed and the existing output image is overwritten. (default)
1 - Skip: The input image is skipped and the existing output image is not affected.
-frames=bN[-eN[,sN]]{;bN[-eN[,sN]]}Specifies the frames and/or frame intervals to process.
bN - N denotes start frame.
eN - N denotes end frame.
sN - N denotes frame increment. If not specified, all frames in the sequence are processed.
-display= 0|1 Specifies whether to display a preview window with the denoising result.
0 - Do not display preview window.
1 - Display preview window. (default)
-autoClose=0|1 Specifies whether to automatically close the preview window after denoising is complete.
0 - Wait for user to close preview window. (default)
1 - Automatically close preview window.
-useCpu=1Forces usage of CPU version even if OpenCL support is found.
-useGpu=0|1|2 Specifies when to use GPU (OpenCL) or CPU version for denoising.
0 - Use CPU. (default)
1 - Attempt to use the best OpenCL device available, and fall back to CPU if unsuccessful. (experimental)
2 - Attempt to use all suitable OpenCL devices, and fall back to CPU if unsuccessful.
-verboseLevel=0|1|2|3|4Specifies the verbose level of information printed to the standard output.
0 - Print no information.
1 - Print only errors.
2 - Print only errors and warnings.
3 - Print only errors, warnings, and informational messages. (default)
4 - Print all output.

 

Advanced Options

 

SwitchDescription
-abortOnOpenCLError=0|1Specifies the behavior of the denoiser when an error is encountered while attempting to use OpenCL.
0 - If an error is encountered, fall back to CPU. (default)
1 - Denoising is canceled upon any OpenCL error.
-strength=NSets the strength of the denoising based on the noise present in the noiseLevel Render Element. Larger values remove noise more aggressively but might blur the image too much. This is the main parameter for controlling the level of denoising. The default is 1.0, which uses the noise in the noiseLevel Render Element as is without adding any additional strength.
-abortOnOpenCLError=0|1Specifies the behavior of the denoiser when an error is encountered while attempting to use OpenCL.
0 - If an error is encountered, fall back to CPU. (default)
1 - Denoising is canceled upon any OpenCL error.
-strength=NSets a value for the strength of the denoising based on the noise present in the noiseLevel Render Element. Larger values remove noise more aggressively but might blur the image too much. The default is 1.0, which uses the noise in the noiseLevel Render Element as is without adding any additional strength.
-radius=NSpecifies pixel radius for denoising. Larger values slow down the denoiser but might produce smoother results. The default is 10 pixels, which corresponds to the Default preset.
-frameBlend=NSpecifies the number of adjacent frames to use when denoising animations. Higher values help reduce flickering between adjacent animation frames. The default is 1, which uses one frame before and one frame after the current frame.
-oclquery="<string>"Explicitly specifies which OpenCL devices should be used for denoising. Examples:
-oclquery="nvidia" - Use only NVIDIA OpenCL devices.
-oclquery="fiji" - Use only Fiji-based AMD OpenCL devices.
-strips=NForces image to be split into N strips for processing. The default is -1 (negative 1), which uses an algorithm to automatically determine the optimum number of strips.
-autoRadius=0|1Specifies whether to automatically adjust the denoising radius based on the level of noise present in the noiseLevel Render Element.
0 - No adjustment. Fixed radius is used for the entire image based on the -radius switch if set, or the default value of 10 if not set. (default)
1 - Automatically adjusts the denoising radius. For very noisy images, this setting might slow down the denoiser significantly.
-threshold=NSpecifies a threshold for denoising when the noiseLevel Render Element is missing. This value is typically equal to the noise threshold for antialiasing in V-Ray. If this switch is not set, the denoiser relies on the noiseLevel Render Element and a threshold of 0.001 is used.
-memLimit=NForces the GPU memory usage limit to N gigabytes. The default value of 0 specifies that all available memory be used.

 

Output


When the standalone Denoise tool is run in the command prompt window, it outputs information about the process, including settings, warnings, progress, and files written.

 

Recommended Settings for 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.

Recommended settings:

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

 

Offsetting the Denoiser Output


 To offset the frame number of the output file, use the the following flag:

-outputOffset=n

This takes an integer n to offset the output denoised frames of animation. The default value is 0, which does not offset the frame numbers.

For example, the following flags can be added to output frame numbers 0010, 0011, 0012, ..., 0030:

-frames=0-20 -outputOffset=10

Negative integers can be used as well. The following flags can be added to output frame numbers -004, -003, -002, ..., 0016:

-frames=0-20 -outputOffset=-4