I made a simple material to reproduce the issue, but in summary, I made a cube and paint multiple vertex color regions on it, and the material should show green in the region is painted and red in the rest. When I select the channel using the channel mask node, it works as expected for RGB, but not for alpha, and when I connect the alpha directly from the vertex color channel, it works as expected.[Image Removed]
Steps to Reproduce
Change the static switch UseAlphaDirectly, the check is on, it works as expected, not using the channel mask node.
Since it works when I make the connection directly, I imagine it’s a bug in the channel mask node, or am I wrong?
Hi,
I can indeed reproduce the issue you are seeing.
I’m fairly certain this is not intentional behaviour, and what you are doing should be supported. There also seems to be no existing report logged for this issue, so I have created a new bug report. Once this bug tracking link goes live it will be available to view here, but it’s worth noting that this may be in 1-2 weeks as Epic are currently on break and this is a manual process.
I think you have identified the most straightforward workaround, which would be to pull the Alpha value directly from the Vertex Color node.
Thanks,
Hayden