Color Correction

PresenZ for V-ray and 3ds Max will automatically export your V-ray frame buffer settings into a vfbColorSettings.vccglb file.

../_images/vfbsettings.PNG

When you use the batch render function and leave the “Merge files after rendering” option on, you won’t have to worry about it further. The merger will automatically use your VGB color correction settings.

../_images/batchrender.PNG

Alternatively if you are not using the automatic merge, and you wish to assign the vfbcc file youreself, you can do so by using the presenz_merger_UI.exe. More info here.

Open Color IO Support

OpenColorIO (OCIO) is a complete color management solution geared towards motion picture production with an emphasis on visual effects and computer animation. OCIO provides a straightforward and consistent user experience across all supporting applications while allowing for sophisticated back-end configuration options suitable for high-end production usage. OCIO is compatible with the Academy Color Encoding Specification (ACES) and is LUT-format agnostic, supporting many popular formats.

This documentation won’t describe how OCIO works and what it works with. Please check http://opencolorio.org/ website for this.

The merger is using OCIO in order to manage the color spaces. All the PresenZ renders are done in linear space, and are merged as such.

If you want to create a specific grading, one possible pipeline is :

  • Use Nuke (https://www.thefoundry.co.uk/products/nuke/) or another OCIO-compatible compositing software (ie. the openSource software Natron https://natron.fr) to create your grading from a standard, linear, 2D render of your VR scene.

  • Export your grading to a OCIO config file (please check your compositing software documentation for more information).

  • Set your OCIO variable properly.

    • Linux
    export OCIO="/myOCIOConfigLocation/config.ocio"
    
    • Windows
    set OCIO="c:\myOCIOConfigLocation\config.ocio"
    

Assigning an OCIO profile in the PresenZ Merger

Inside the merger you can see that there are OCIO files already present. This is the default one we are using to write from Linear to Linear.

../_images/lineartoSrGB.PNG ../_images/mergerfile.PNG

.

../_images/ocioconfig.PNG

You can open the config.ocio in any text editor and have a closer look at one of these color profiles. The luts folder is where these profiles are stored.

We are primarily interested in these colorspaces. The first one you see is the linear one.

../_images/linear.PNG

Warning

This one is very important as the merger expects a linear colorspace inside the .przRender files. If you are considering on creating your own one make sure to include this one:

colorspaces:
- !<ColorSpace>
  name: linear
  family: ""
  equalitygroup: ""
  bitdepth: 32f
  description: |
    Scene-linear, high dynamic range. Used for rendering and compositing.
  isdata: false
  allocation: lg2
  allocationvars: [-15, 6]

Let’s take a look if we want to go with a different profile on how exactly we do this. If you have a custom made OCIO config file you can also apply these steps.

  • Open a windows command prompt
  • Specify the path to your merger, and where the ocio files are located Cd C:utilitiesmergerlocation
  • Drag the presenz_merger.exe : you will see all the options that can be declared with the presenz merger. The one’s we are interested in for this particular part are: --OCIOconfig, and --applycolorspace .
  • --OCIOconfig : is the path to the config.ocio file
  • --applycolorspace : is the name of the colorspace inside the ocio.config file

The following line is an example code.

*E:\OCIOLearning*>presenz_merger.exe E:\OCIOLearning\przRenders_Testfiles --OCIOconfig E:\OCIOLearning\ocio\config.ocio --applycolorspace Cineon

  • The merger
  • The file location of the przRender files that need to be merger ( VR_0 - VR_8)
  • --OCIOconfig + the location path of the config.ocio file
  • --applycolorspace + the name if the colorspace

As you can see, once you started the command the OCIO is converting from linear to Cineon

../_images/convertinlineartocineon.PNG

From the same render result from before we can do a color correction by re-merging the rendered przRender files.

The result side by side:

../_images/sidebyside.png