Why does unreal engine phorealistic character project file has roughness and specular map?

hegvbwkeuyrv

i was just testing out and reading the doecumentation, but why does it has roughness and specular? isnt it basically the same thing? why dont they just blend it together

poopipe

no it isn't.   check the unreal documentation, there's a section on it in there somewhere

hegvbwkeuyrv

there is .-. check it again

JordanN

"The specular map scales the amount of specular highlight visible across the surface of the skin. It is important to note that the default value for specularity is 0.5. This map boosts specularity at areas where the skin may be stretched a bit tighter, and dampens it in areas where we don't want to see reflection, such as the center of pores and within wrinkles. (CH2_exp04_merged_spec_f_FC_FINAL)"

https://docs.unrealengine.com/en-us/Resources/Showcases/PhotorealisticCharacter

UE4 always had the Specular channel which is a legacy feature but still has a bit of usefulness in controlling lighting. 

The roughness channel corresponds with PBR in that it actually controls the level of smoothness on an object. So human sweat and pores wouldn't have the same specular intensity.

hegvbwkeuyrv

oowh so in other words specular is like a secondary specular for area such as the pores?

JordanN

It's been a while since I used it but specular acts more like an IOR for non-metals. It increases or decreases the ability to reflect light. It can also act as a cavity map oddly enough. 

But more or less, it's just an extra lighting tweak. The Roughness channel is where all the PBR magic happens and is the most accurate.

poopipe

refer to this - where it's argued about and then explained 

http://polycount.com/discussion/199192/how-to-use-the-specular-color-output-in-sd#latest

hegvbwkeuyrv

@JordanN is it the reflection occlusion thing? cuz the pores doesnt get specularity inside i read somewhere

Obscura

To clear everyones confusion up on this, "specular" input lerps the reflectance between 0 and 100. It has a curve kind of thing applied on it, because when its set to 0.5 it gives the dielectric reflectance which is 4%. When its 1 you get 100 % reflectivity. Setting this lower than .5 gives lower reflectivity than a non material should have but in some cases this is desirable and can look nice. When you have metallic of 1 this input does nothing because you already have a fully reflective material -and tint from the base color. Now im not totally sure about this but I think full specular instead of full metal probably gives you non tinted reflections. You can always try thing out to see what happens... so take this input as a fine tuner but generally your specular values in unreal should be around .5 +- a little.

Alex_J

https://www.youtube.com/watch?v=sxLRi7Lbtxs&list=PLZlv_N0_O1gbQjgY0nDwZNYe_N8IcYWS-&index=5

this gives a more beginner friendly explanation. Third or fourth video in the series. Easier to see and understand than describe.