Looked through the automotive materials that epic released, very cool. Noticed that some materials have both roughness and a specular input. From my understanding, you typically choose rough/metal, and specular was just legacy stuff… The specular input threw me off a bit and don’t understand why. Does anyone know the reason?
You always need roughness. Specular for non metals are typically uniform, very low intensity and non colored.(in range of 0.02-0.06) For this reason material system actual remap specular to range of 0-1 and default to 0.5. This material specular value is just multiplied with 0.08 to get physical based specular values. Most common materials does not need anything to plugged to specular slot. Some materials need constant value to be plugged to specular.(0.255 for water). Sometimes you want to bake micro occlusion texture and you need to multiply base color and specular with this texture.