Smoothness (Smoothness / Smoothness / Roughness) is a technical term that is extremely important in the rendering and optimization of game graphics (technical art). Explanation of the most important texture factor in Physically Based Rendering (PBR), which is a parameter that determines the fine smoothness (smoothness) of the surface of a material, and controls whether light reflection is clearly concentrated in one point or spread out blurry around the surroundings.
Real-world analogy: The surface of a material may be a freshly waxed gym floor (Smoothness 1.0) or a sanded wood surface (Smoothness) 0.0)” Smoothness scale
Smoothness is a ``micro-smoothness slider'' that shows how flat and smooth the material's surface is. When the value is set to 1.0 (smooth), the beam of light bounces back beautifully without any disturbance, so the surrounding scenery (Reflection Probe) and the sun are reflected beautifully in one spot, extremely sharply, like a mirror. On the other hand, if you set the value to 0.0 (rough), the light will be reflected diffusely in all directions due to the intense micro bumps, making the reflected highlights blurry and gently spreading out to the surroundings, giving it a flat, dry texture.
Illustration: Smoothness (Smoothness / Infographic that clearly illustrates the basic processing flow and mechanism of smoothness/roughness) in Japanese notation
Detailed mechanism and operating principle
Set the material's "Smoothness" parameter appropriately (high value of 0.9 or more for mirrors and metals, low value of 0.2 or less for concrete and wood). In addition, fine scratches and dirt on the surface are pasted as a "Smoothness texture" to partially change the Smoothness.