Problem summary It is possible to create a custom LUT in Nuke by applying your grade to a CMSTestPattern node, then writing this out to one of many formats using the GenerateLUT node.
This LUT can then be reapplied in the script using a Vectorfield node.
One issue that has been discovered, is that when a .cms file is created within a ACES colorspace, when re-interpreting this through a Vectorfield node the results do not match to the original grade.
Note: This issue does also occur in the Nuke default colorspace, although can be fixed by setting the viewer settings and to 'use GPU for inputs when possible'.
Customer reported version nuke.12.2v3
Customer reported platform n_a_windows
Steps to reproduce
1) Open a new session of Nuke and switch the colorspace to OCIO/ACES
2) Create a ColorBars node, and then a create a custom grade to this with a Grade node
3) Create a CMSTestPattern node, and copy the Grade node to start a new tree.
4) Connect a GenerateLUT under the copied Grade node, and within the GenerateLUT node, set a location and file as .cms and execute this with the Generate and Write LUT File button
5) Import the custom .cms LUT using a Vectorfield node
6) Plug in the Vectorfield node to the ColorBards nodeand compare the result with the original Grade node. Result: The .cms LUT does not match the grade.
7) Repeat the above process using a .cube LUT to see how this should work correctly
Expected behaviour The .cms LUT should match the original grade, when using a Vectorfield node to re-apply a generated LUT in ACES colorspace
Actual behaviour The .cms LUT does not match and there is a significant difference in the results.
Workaround Unknown. Avoid using .cms files at this point in time in ACES colorspaces, in favour for .cube LUTs if possible.
Reproduced by support This bug has been reproduced in: Nuke 12.2v3 - Windows 10 - MacOS 10.15.6 - CentOS 7 Nuke 12.2v1 - Windows 10 Nuke 12.1v1 - Windows 10 Nuke 12.0v1 - Windows 10 Nuke 11.3v1 - Windows 10 Nuke 11.2v1 - Windows 10 Nuke 11.1v1 - Windows 10 Nuke 11.0v1 - Windows 10 Nuke 10.5v1 - Windows 10 Nuke 10.0v1 - Windows 10 Nuke 9.0v1 - Windows 10 - MacOS 10.15.6 - CentOS 7
Earliest version tested Nuke 9.0v1 - This issue appears to be in all versions of the product
