Problem summary When using a DirBlur node, and setting BlurType to linear, the alpha from the upstream nodes is no longer visible.
Customer reported version Nuke 12.1v1
Customer reported platform CentOS 7
Steps to reproduce
1) Open Nuke.
2) Create a Roto node, and create a Bezier shape.
3) Set the output knob to "rgba" to make the bug easier to see.
4) Create a DirBlur node directly downstream from the Roto.
5) Change the BlurType knob to linear.
6) View the alpha (press A on the Viewer) and notice that the alpha from the Roto isn't visible.
Expected behaviour The alpha should be visible and the Blur should be applied to the RGB channels only.
Actual behaviour When the BlurType is set to linear, the alpha from the upstream Roto is no longer visible.
Workaround Setting both the "channels" and "BlurLayer" knobs to "rgb" appears to give the expected result.
Reproduced by support This bug has been reproduced in: Nuke 12.1v1 - Windows 10 - macOS 10.13 (High Sierra) - Linux CentOS 7 Nuke 12.0v1 - Windows 10 Nuke 11.0v1 - Windows 10 Nuke 10.0v1 - Windows 10 Nuke 9.0v1 - Windows 10 Nuke 8.0v1 - Windows 10 - macOS 10.13 (High Sierra)
Earliest version tested Nuke 8.0v1 - This issue appears to be in all versions of the product