Problem with specular maps

JamesLarden · Jul 2014

Hey PolyCount, a quick question about specular maps, and why the hell mine isn't working?

Recently i've been working on texturing this door for a space enivronment, but the material just doesn't seem to be registering any information from the specular map...

I got really frustrated and decided to just scrap that texture and restart, still didn't work so I literally took a grunge brush on black and painted over the diffuse and plugged it into the specular, and it still does NOTHING.

The specular:

The result:

The nodes:

Literally was as simple as I could make it, which is why i'm so confused that it's not working, I mean there's absolutely no information from the specular map translating on to the model and I made parts on the spec fully black.

Any ideas? It's probably a really simple fix and i'm just an idiot, but help is appreciated.

Thanks for reading.

passerby · Jul 2014

That specular input isnt what you think it is, what you want is the roughness input. Which uses a inverse scale so brighter values == a more rough and less shiny surface.

You really should look into how ue4 does PBR rendering since it is nothign like how things used to work in udk

EarthQuake · Jul 2014

passerby wrote: »

That specular input isnt what you think it is, what you want is the roughness input. Which uses a inverse scale so brighter values == a more rough and less shiny surface.

You really should look into how ue4 does PBR rendering since it is nothign like how things used to work in udk

Well, yes and no.

First off, if you have a metalic object, what you do is put the spec or reflectivity (the map which defines how reflective an object is) in the abledo, and then use a value of 1 (white) in the metalness input. Load a metalness map if you have metals and non-metals (for non metals, put the diffuse color in the albedo, and use black in the metalness map).

Roughness simply defines how rough or smooth the surface is (black = most smooth, white = most rough, in UE4). It does not define how reflective it is. However, due to energy conservation, rougher surfaces will bounce the light in more directions, giving a wider, but dimmer highlight. This does not mean the surface is any less reflective though, the reflection is simply spread over a larger area.

Reflectivity is fixed at 0.04 for non metals, and defined directly in the albedo for metals.

passerby · Jul 2014

@eq i know how the ue4 brdf works just wanted to use terms he was used to from the old system. Already know about the whole roughness vs specular thing, and how ue4 uses the metalness map to either sample the specular from the albedo, or from a hard coded value

EarthQuake · Jul 2014

Well, that was for his benefit more than yours. I think telling him to plug his "spec" map into the roughness/gloss is just confusing and doesn't really help explain any of it.

Heres a link to the official docs as well: https://docs.unrealengine.com/latest/INT/Engine/Rendering/Materials/PhysicallyBased/index.html

passerby · Jul 2014

true, you should also point him to your camera tutorial as well http://www.marmoset.co/toolbag/learn/pbr-practice.

Lots of great stuff there

JamesLarden · Jul 2014

Thanks for all the help guys, really appreciated.

I'm gonna take a look at the links you posted now and have a play around with it, thanks again!

Problem with specular maps

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