We create objects with varying level of details (LODs) to increase the efficiency of rendering. For objects that are closer to the player, high LODs objects are rendered. Objects with higher LODs have a higher number of polygons. For objects that are far away from the player, a simpler version of the object is rendered instead.

Artists can create different LOD versions of the 3D object using automated LOD algorithms, deployed through software or manually reducing the number of vertices, normals, edges in the 3D Models, to create a lower polygon count model. When creating models of different LODs, note that we always start by creating the most detailed model with the most number of polygons first and then reduce the number accordingly to create the other LOD versions. It is much harder to work the models the other way around. Do remember to keep the UV coherent when working with objects with different LODs. Currently, different LODs need to be light mapped separately.

The following image is taken from http://renderman.pixar.com/view/level-of-detail and very clearly shows the polygon count based on the distance away from the camera: