Nuke Gizmo for Khronos PBR Neutral Tonemapper

In the recent years different approaches to color management in CGI appeared – from ignoring it to linear workflow to Rheinhard tone mapping to ACES to AGX and now the new Khrono’s PBR Neutral Tone mapper.  After experimenting both with ACES and AGX I found that these can work great for workflows such as feature film and probably many more but they did not suit Deepframes needs which are:

• keep it simple in 3ds max, nuke, AE

• work with RGB assets from clients, existing textures, stock models

• attractive, realistic, photo like look

Simply put what Khronos PBR Neutral Tone does is:

  • increase contrast of the image in the mids and fixing the sometimes washed out look of purely linear renders
  • increase dynamic range the bright highlights providing a bit more of a human eye experience
  • preserve saturation and color accuracy which is important for product rendering where colors from printed labels

Comparison with Linear workflow, with PBR Neutral

Nuke Gizmo Parameters

The nuke gizmo is based on a Blink script implementation of the original algorithm and can be used in the foundry nuke as an alternative to an OCIO workflow.

The gizmo provides 4 parameters for optional finetuning of the image and automatically clamps negative input values which could otherwise result in unwanted artifacts. The default values were defined by Khronos group and are a good starting point.

 

 

The F90 paramter can be used to increase the contrast in the lower and mid value range of the image. A value of 0.0 disables the effect and a value bigger than 0.04 is increasing the effect.

 

The Ks1 parameter is by default 0.8 and can be used to control when the highlight compression starts. According to the paper it starts at Ks1-F90 which is 0.76 with default values.

 

The Kd parameter controls the amount of highlight compression. Lower values than 0.15 increase the compression even more.

The blend result paramter can be used to blend the effect with the original image and was not part of the original formula. A value of 1 means the formula is used, a value of 0 disables the effect entirely.

Download Nuke Gizmo

More Information about PBR Neutral

If you want to read more about Khronos PBR Neutral you can find them on Khronos.org

and on the official github page