Level of detail (LOD)

LOD is shorthand for how detailed a 3D model, or a single element in it, is meant to be. In architecture it turns up in two different contexts, and keeping them apart matters: in BIM it describes how mature the model is at a given project stage, while in rendering and game engines it refers to simpler versions of an object used further from the camera.

LOD in BIM

In BIM projects LOD usually stands for Level of Development. It defines whether an element exists only as an approximate mass or is resolved enough, with dimensions, materials and connections, to be built. These levels are referred to by numbers such as 100, 200 and 300, and contracts use them to make clear what the model must contain at each stage. That way nobody treats information that is still provisional as if it were final.

LOD in visualization

In rendering and real-time applications LOD means versions of the same object at different weights. A tree close to the camera uses its high-polygon model; the same tree in the distance is swapped for a copy with a few hundred polygons. Real-time engines make this switch automatically. In offline rendering the person building the scene picks simple models for distant blocks, rows of trees and crowds. Done well, nobody notices the difference and the scene gets much lighter. We cover ways to prepare a model with this in mind in our article on SketchUp model preparation before rendering.