Nuke native implementations of AgX.
| tool | description |
|---|---|
| AgXcTonescale.nk | tonescale algorithm of AgX (blink script based). |
| AgXcDRT.nk | full image rendering pipeline for AgX |
| PrimariesInset (in external repo) | gamut remapping algorithm, referred as "inset" |
Common for all tools :
- Open the desired
.nkfile in GitHub or download it locally - Copy to clipboard the whole content of the nk file
- Paste into any opened Nuke scene
As of right now all tools are independent of each others and don't have external dependencies.
- Tools were developed for Nuke15 but MIGHT work on lower versions.
- Tools were developed on Windows but SHOULD work on other platforms.
- Tools use the following nuke features :
- blink script (compatible with non-commercial version >= 14.0)
- python for some internal components but static (i.e only triggered on user press)
The tonescale is the per-channel "s-curve" algorithm that is remapping the luminance range of its input data.
The algorithm is the same as per originally defined by Troy: https://github.com/sobotka/AgX-S2O3/blob/daffcfa18edaa7172ce549cd25e80b7faadd8292/AgX.py#L192
PlotSlice node by Jed Smith
The tonescale expect log-encoded data as input.
The initial formula to calcule the x and y pivot specified by Troy was:
min_EV = -10
max_EV = +6.5
x_pivot = abs(min_EV / (max_EV - min_EV))
# >>> x_pivot = 0.6060606
y_pivot = 0.50Encode "open-domain" data to display.
Algorithm is based on the original Troy implementation with various additions, some personal, some from other AgX tinkerers (see credits).
For a full breakdown see my post on Blender-Artist AgX thread.
Expect "open domain" data as input, with a linear BT.2020 D65 encoding.
Output a display-referred result bounds to the specified display that can be directly previewed or written to disk without any more processing (example: make sure the nuke view-transform is disabled when viewing its output).
It is possible to visualize a 2D "slice" plot of the process by checking "Show Plot". A linear 0-1 ramp is being plotted and allow to visualize the effect of the tonescale and other grading operations.
- The y axis is in [0-1] range and represent pixel "intensity".
- The x axis is a 2D slice of the ramp where lower values represent dark values of the input and high values the white ones.
"Luminance mapping" of the image with additional grading possibilities to emulate the color-shift of the analog film print process. Note the process MIGHT actually have no similarity at all with the film print process but the name was found to be pertinent and stayed, in lack of better term.
Original AgX implementation applied the tonescale a single time. This one can apply it 2 times, producing an extra softness that can be comparable to the look of analog film.
Control the amount of chroma purity in bright values where higher values will produce a less chroma-intense look.
The default value of 0.4 might be a bit strong.
Control the contrast of the 2 tonescale curves. It is interesting to see them as working in tandem.
The contrast second only works when Apply Double Tonescale is of course checked .
The tonescale section offer a creative control called "print contrast" that allow
to shift the tones of your image. The intended use is to use different R-G-B ratios
on the print contrast control, with the additional pivot control to refine further
the look (do not hesitate to check Show Plot to have an alternative representation
of your changes).
Pick the target display the image should be intended to be displayed on.
Check the ../.dev/implementations/nuke directory.
- Troy Sobotka: of course for the original AgX algorithm
- Jed Smith: nuke-colortools.
- flannelhead and other darktable developers: darktable-org/darktable#15104
- EaryChow and anyone involved in the development of the Blender variant: https://blenderartists.org/t/feedback-development-filmic-baby-step-to-a-v2/1361663/