How to enable specular color


How does one enable specular color? In the paper Real Shading in Unreal Engine 4, Karis writes:
“After long discussions, we decided to continue to support the old DiffuseColor/SpecularColor as an engine switch in order to maintain quality in Fortnite, since it was far into development.”

This would be useful to fake some post process effects in seperate transparency materials. Also would this switch interfere with the standard physically based shading?

Hey jgm,

I just took a quick read over the presentation myself, and from my understanding the old shader was not as physically accurate as we would have liked, and didn’t have the robustness we wanted moving forward with a PBR shader.

We kept the old shader for Fornite since it “has a non-photorealistic art direction and purposefully uses complementary colors for diffuse and specular reflectance, something that is not physically plausible and intentionally cannot be represented in our new material model.”

“We don’t feel that the new model precludes non-photorealistic rendering as demonstrated by Disney’s use in Wreck-It Ralph, so we intend to use it for all future projects.” In short, it will change a bit of your PBR but will not drastically change your overall look of your materials.

"In the case of the new shader, roughness is going to adopt the old specular color. “There is one situation I have seen a number of times now. I will tell artists beginning the transition to using varying roughness, “Use Roughness like you used to use SpecularColor” and soon after I hear with excited surprise: “It works!” But an interesting comment that has followed is: “Roughness feels inverted.” It turns out that artists want to see the texture they author as brighter texels equals brighter specular highlights. If the image stores roughness, then bright equates to rougher, which will lead to
less intense highlights.”

The quotes I grabbed should be able to answer your questions straight forwardly.


Thanks for the comprehensive response!