Why does Unlit Viewmode show Specular contribution?


I just noticed that in UE 4.25.3 when using Unlit Viewmode, a Material that’s pure 0/0/0 in BaseColor and Emission still shows up as 0,01799/0,01799/0,01799 in the Pixel Inspector under HDR (and various non-zero in all different types of analysis mode).

First I thought this might be some Tonemapping Problem or such, but as it turns out it’s because Unlit Viewmode also shows Specular Values, and those were responsible for raising the Values above 0.

I dug around a bit and found some post from 2014 where someone said this might be intentional, but Ryan wrote Epic will take a look at it: Lit vs UnLit : why displaying the specular channel ? - UE4 AnswerHub

Is this really intentional, or some (re-introduced) bug?

I think with an older engine version (about 2 years ago) this wasn’t happening, because I used Unlit Mode + Expressions in the Emissive Slot to test custom gradients (built upon using World Space trickery), and don’t remember running into any problems back then - but I might be wrong.

I know for testing purposes I could just temporarily deactivate the Specular in Lighting Component, but for my limited rendering knowledge, it makes no sense to show Specular in Unlit.

Thanks a lot!