ID 476625 - Expression linking color values to Rotopaint's color knob displays the wrong result in the Viewer

Problem summary
Expression linking color values to Rotopaint's color knob displays the wrong result in the Viewer.

Customer reported version
Nuke 13.0v1

Customer reported platform
Windows 10

Steps to reproduce

1) Open Nuke.

2) Create a Constant node, and press the '4' button on the color knob to display multiple values.

3) Set different values in each of the R, G, B and A fields. 

4) Create a Rotopaint node, then create a Bezier shape in the Viewer.

5) Connect the RotoPaint to the Viewer.

6) Press the '4' button on the RotoPaint's color knob as well.

7) Expression link the color knobs by Ctrl+dragging the animation button

 (from the Constant node to the RotoPaint).

8) Mouse over the Bezier shape, and compare the RotoPaint's knob values with the values displayed in the Viewer.

​

Expected behaviour
The RGBA values should be correctly displayed in the Viewer.

Actual behaviour
The RGBA values in the Viewer are not set to the corresponding value, despite what is displayed in the RotoPaint's control panel.


Workaround
You can manually change the expression so it links to the correct channel, instead of just the knob name. You can do this by right clicking the knob > Edit Expression. Then change the expression from:

parent.CurveTool1.intensitydata

To the following:

parent.CurveTool1.intensitydata.r

And repeat this process for the G, B, and A values.

Reproduced by support
This bug has been reproduced in:
Nuke 13.0v1 - Windows 10 - Linux CentOS 7 - macOS 11.3 (Big Sur)
Nuke 8.0v1 - Windows 10

Earliest version tested
Nuke 8.0v1
- This issue appears to be in all versions of the product