Level Of Detail (LOD)
LODs, or Levels of Detail, are the different states of models within games. As a general rule of thumb, the further the object, the lower the level of detail. For example, a gun that may be repeated a lot throughout a first person shooter game would be much more detailed when the player was holding it, than when an enemy in the distance was shooting at the player.
The top gun (LOD 1) would likely be used as the players’ weapon, whereas the bottom gun (LOD 4/Low Poly Sketch) would likely be used as the gun for an enemy in the distance.
The reason that game engines use these different LODs, so that they can focus the power of the system on the important visual aspects of the game. It is more important for the objects closer to the camera to be significantly more detailed, compared to objects further away, as when the distance increases, it becomes much more difficult to see tiny detail.
LODs aren’t just related to 3D models however. Textures and other visual elements also usually have LODs. The further away from the object the player/camera gets, the lower the resolution of the texture. For example, the texture of a character may be 2048px x 2048px when in close proximity to them, but when from a distance , it will be impossible to notice the tiniest details of the texture, and so it may drop to a texture size of something as small as 512px x 512px.
The labelled picture below shows the different LODs of
Call Of Duty: Black Ops II Multiplayer. The players’ gun is significantly more detailed
than the other characters’. The characters in the background are even less detailed, both model, and texture wise. The UAV Drones are another good example of LODs in games. The closer one is much more detailed than the one in the background, since the far one doesn’t
need to be as visually appealing.
The screenshot of GTA V shows two LOD extremes. The jet is at LOD 1, with the model and texture being fairly decent resolution, whereas the road and buildings below are barely even there. The buildings are just blocks, with no detail, other than the diffuse and normal maps. The same goes for the road. At ground level, the roads of GTA V have signs and central reservations, but none are visible from this distance. All detail is via the diffuse and normal maps again. The cars on the roads are also of very low detail, so much so that they are pretty much just boxed on the road.
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