Signed Distance Field also know as SDF, is a technique developed by Value Valve company that uses low resolution textures to display extremely high resolution looking fonts and decals. Valued Valve used SDF in their game engines that run Half-Life 2, Counter-Strike 2 and etc. SDF is so effective that no matter how many times the font or decal is zoomed in, it will always look crisp and sharp while using very small textures.