Level of Detail
|Level of Detail||
Whether explicit or behind-the-scenes, all major 3D game titles use “Levels of Detail” for their render output, sometimes listed as “LOD.” This is usually a setting that gamers have no control over, though it sometimes makes an appearance in .ini files or game settings. Nonetheless, LOD has profound impact on game performance and, when implemented correctly, can substantially optimize performance for lower-end hardware. We'll explain this in more depth below.
Level of Detail impacts the count of vertices or polygons displayed in an on-screen object, but can also be used loosely to refer to the resolution of a texture drawn to a 3D object. We first discussed LOD with Chris Roberts in the early phases of Star Citizen, who noted that it doesn't make sense to display a multimillion-polygon object on screen with all polygons drawn. The farther you are from an object, the more of that object will fit on the screen and the less granular detail is required. The closer an object, the more detail is required to prevent blurring or jagged edges, so a higher LOD is used – but fewer other objects are on the screen simultaneously (or may be blurred if DOF is enabled).
(Image source: Wikipedia).
On the texture side, mipmapping can be used to create smaller texture resolution maps of a larger texture. A sign might use a 256x256 texture when up close, but revert to a 128x128 texture in the mipmap when the user is farther away (too far to be able to read the sign or require such gritty detail).
(Image source: GamersNexus).
Both mipmapping and lower LOD objects are what allow games to use high-poly, high-detail objects and textures without encumbering the GPU with distant object rendering.
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