Signed Distance Field also know as SDF, is a technique developed by Valve company that uses low resolution textures to display extremely high resolution looking fonts and decals. Valve used SDF in their game engines that run such games as 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. This allows fonts and decals in game to have much higher quality with low memory compare to using regular high resolution textures.For more detailed information please read Valve's publication: http://www.valvesoftware.com/publications/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf Examples: