Decal specular channel not working

[shadmar]

Trying to make wet blood stains but, fragData2.a seems to have no effect on decal specular rendering.

Blood looks like plastic with no specular, is this a bug?

[Josh]

You are correct. This is by design and you are the first person to point it out. Adding another channel for specular would require an additional render texture so I have been sitting on this and hoping I can find a way to make all channels use the first channel's alpha value for the blend equation. Not sure what I will do yet, but this situation is something I had in mind because sometimes you want to make shiny decals like this.

[nick.ace]

Why can't you read in the emission texture and do blending manually?

 

Actually, why do you even have an emission color at all? It generally doesn't make sense to split it apart since materials generally should have the same emission and diffuse color. I haven't seen other deferred renderers do this. You would also save 3 channels here, and two of them can then be used for a velocity buffer for motion blur, and you would have one last value for something else (perhaps emission power?). Or better yet, swap the emission power and the roughness since roughness probably has a larger impact on shading quality.