Detail Map (Detail Map) is a technical term that is extremely important in the rendering and optimization of game graphics (technical art). Explanation of the technology to create a texture that does not blur even when the camera is extremely close to the main texture (low resolution) by multiplicative synthesis of patterns (high resolution) such as fine noise, cloth fibers, and metal scratches using extremely fine UV tiling.
Real-world analogy: A double bottom textured surface of a huge poster (main image) in which ``fine rough paper fibers (detail map)'' that are visible only when you get close to it are superimposed on a separate layer in an ultra-microscopic manner
Detail Map is a double texture protection filter that repeats and overlays the ``microscopic textures (the mesh of the threads of jeans, the fine gravel of concrete)'' to prevent it from appearing when the camera approaches a few centimeters.'' By reducing the main texture to a light size of around 1024 and repeating (tiling) and multiplying the ultra-light 256 size image for details 100 times, you can save memory more than 10 times compared to pasting a 4K texture as is, and achieve an amazing ultra-high resolution that does not appear blurred no matter how much you zoom in.
Figure: An infographic that clearly illustrates the basic processing flow and mechanism of Detail Map (Detail Map) in Japanese notation
Detailed mechanism and operating principle
Apart from the main color texture, prepare a small "Detail Map (monochrome or normal image)" that expresses cloth mesh and metal scratches, and blend it with a fine UV tiling value such as 20x in the material's detail settings.