Reporting this as an issue pending any additional information or documentation.
Assuming there isn’t some user side error, the material debug buffers appear to be suggesting a material internal and / or interface issue.
Given the settings I’ve supplied to the instance material in the linked thread I would expect my red channel to be sampled, transformed, and output to both the specular and AO material channels.
The public material interface / UX should really should be far clearer than it is, and I’m still not convinced it’s working correctly. I’m only left to assume that internally it’s not actually piping the Red channel modifications to the Material Ambient Occlusion output, which multiple sets of parameters affect the Specular channel in ways that simply aren’t intuitive.
My tests reveal that the AO namespace parameters (AO_Min, AO_Max, etc) also affect the composite specular result. Yet the name implies that these properties affect discrete material output channels.
This has to be bug, right? There is no combination of settings I can find which yields clean, predictable results in both the AO and Specular material channels.
Maybe I’m missing something that is supposed to be obvious?