lods

LOD, or Level of Detail, is a set of techniques in real-time 3D computer graphics that reduces rendering workload by varying the geometric complexity of objects based on their distance from the camera or their screen-space size. The aim is to preserve visual quality where it matters while lowering polygon counts where it is less noticeable.

A typical LOD setup uses multiple representations of a model, ranging from high to low polygon counts. These representations can be created manually or generated automatically through mesh simplification (decimation) algorithms. A more general framework is progressive meshes, which allow a continuous sequence of detail levels and can support streaming of geometry as needed.

Switching between LODs is usually governed by distance thresholds or screen-space error metrics. To minimize visual disruption, techniques such as blending between LODs or morphing vertices (morph targets) can be employed. For very distant objects, impostors or billboards may substitute complex geometry. LOD work is often complemented by texture-based strategies, including mipmapping and other texture LOD methods, and by other performance techniques like frustum culling and level streaming.

Applications of LOD are widespread in video games, simulations, virtual reality, and scientific visualization, where rendering efficiency is critical. Modern engines typically combine LOD with other optimizations and may leverage hardware features to manage geometric detail, shading, and texture resolution in a coordinated way.

History and notes: the concept originated in the late 20th century as a practical approach to real-time rendering. A foundational development was Hugues Hoppe’s Progressive Meshes work in the mid-1990s, which formalized scalable, continuous LOD and influenced subsequent graphics pipelines.