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While some RenderMan plugins integrate the Denoise feature, RenderMan does ship with a tool for processing images after rendering. Keep in mind that the appropriate AOVs must be included for the Denoise filter to work.


Denoising does not affect the alpha channel of images. Doing so can cause artifacts and halos to form and is therefore avoided.

GPU Acceleration

Denoise can attempt to use GPU acceleration. You can activate this mode by adding --override gpuIndex 0 to the command line, where the number indicates which GPU to use.  In a single-GPU system, this will always be 0. If no compatible hardware is found it will failover to CPUs. Using the GPU requires CUDA 7.5 (compute capability 2.0 or later) and a capable graphics card with support.

Enabling GPU Denoise

Globally you can enable the GPU features by changing the .json file here: $RMANTREE/lib/denoise/default.filter.json

gpuIndex corresponds to the GPU installed to use for denoising. If -1 is used, it will use the CPU instead.

Code Block
    "//": "Global settings which apply across all filteres/kernels:",
    "filterLayersIndependently": false,      "//": "If true, filters each render output using weights affected",
                                             "//": "by its color, reducing artifacts but violating additivity",
                                             "//": "and imposing a speed and memory penalty.",
                                             "//": "If false, uses the same weights for all to-be-filtered layers, ",
                                             "//": "ensuring additivity.",
    "splitSpecularDiffuse": true,            "//": "If true, filters specular and diffuse separately",
    "splitSpecularDiffuseVariances": true,   "//": "When splitSpecularDiffuse and the file has diffuse_var and",
                                             "//": "specular_var layers, use them.",
    "warpType": "linear",                    "//": "cross-frame warp method: linear or nearest",
    "gpuIndex": 0,                           "//": "use GPU denoising on graphics card #0",

Denoise Flags

Running denoise -h results in the following 'help' output:

Code Block
-o name            Outputs to shotCam_name.exr instead of shotCam_filtered.exr
-n                 Output basename is based on variance image rather than
                     to-be-filtered image
--outdir dir       Outputs to this directory instead of the input file's
--filtervariance   If a mix of variance and non-variance files are specified,
                     output includes filtered version of variance's color
                     channels too
--crossframe       Cross-frame sequence mode: filters across frames
--skipfirst, -F    Doesn't output an image for the first frame
--skiplast, -L     Doesn't output an image for the last frame
--layers           Filter only render output layers matching these names.
                     Supports wildcards ?, *, [...].  E.g., --layers 'diffuse,
-v name            Uses motion vectors with crossframe mode.  Motion vectors
                     are located based on the variance filename, changing
                     "/variance/" to "/<name>/", "variance." after "." or "_"
                     to "<name>."  Note that "-v variance" will use the
                     motion vectors from the variance file itself
-f configFiles     Filter definition file and/or overrides.  Separate multiple
                     files with '+' or use multiple -f's.  Use -H to list
                     available files.  The default baseFile.filter.json is
-H                 Lists all available filter config files
--override key val Override a value from filter definition file.  Can use
                     multiple times.  If last flag, follow with -- before input
                     file names.  Examples:
                       --override strength 0.5
                       --override 'kernels[1].params.sigma_albedo' 0.05
                       --override debugPixel '[336, 209]'
-t nthreads        Number of threads; default is number of cores on machine
-h, --help         Help
--version          Version information





The Denoise tool comes with three filter presets:



Used to filter based on image alpha.


Used for volumes rendered alone onto transparent black.


Code Block
denoise --override 'kernels[0].params.sigma_albedo' 0.07 -- shot.variance.001.exr

Optional Pre-made Filter Controls

There are also several override filter settings that can be combined with the base filters. Notice these are named as filteroverride.filterLayersIndependently. filteroverride.json





Turns on both unpremultiply by color and features.

Example Usage

Code Block
denoise -f +noDepth.filteroverride.json shot.variance.001.exr
Code Block
denoise -f volume.filter.json+fireflyKiller.filteroverride.json+linearWarp.filteroverride.json shot.variance.001.exr

Custom Overrides

You may also create your own filter overrides based on your needs. Note that RenderMan looks for the filters under the RenderMan ProServer install directory in lib/denoise/ The following example creates a control that alters the overall strength of the denoising effect.


Note that increasing the filter strength may take longer to process the image result.

Custom Filters

Similar to creating custom overrides, you can copy the default.filter.json configuration (or one of the others) to a new file and edit it. For example if you saved it to local.filter.json you could then use it with the following command: