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.
Denoise can attempt to use GPU acceleration. If no compatible hardware is found it will failover to CPUs. Using the GPU requires CUDA 7.0 (compute capability 2.0 or later) and a capable graphics card with support.
denoise -h results in the following 'help' output:
The Denoise tool comes with three filter presets:
Used for most scenes. This filter achieves reasonable results without changes.
Used to filter alpha.
Used for volumes rendered alone onto transparent black.
It's important to use the volume filter on images containing isolated volume elements or you may introduce more noise into the filtered image using the default filter.
You can override the default filter and settings using the
--override flags. You may also set a different environment override. The below examples are the same result with different methods.
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.
Filters EXR layers individually.
Removes fireflies (bright pixels) from an image.
Sets the noise filter's prev/next frame warp type to 'linear'.
Sets the noise filter's prev/next frame warp type to 'nearest' (non-interpolated).
Turns off dividing by the albedo.
Turns off use of the 'depth' feature to cue the noise filter.
Turns off the firefly killer for the noise filter.
Defines the parameters of the noise filter, using separate diffuse vs specular variances.
Turns off unpremultiply by color options.
Defines the parameters of the noise filter, using separate, diffuse vs specular variances.
Turns on unpremultiply by color.
Turns on both unpremultiply by color and features.
Custom Filter Controls
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 /lib/denoise/ The following example creates a control that alters the overall strength of the denoising effect.
Saved as strength0.2.filteroverride.json you can then use the following command:
Note that increasing the filter strength may take longer to process the image result.