fade, essentially implementing distance fog. Video games using LOD rendering avoid this fog effect and can render larger areas. Some notable early examples of LOD rendering in 3D video games include The Killing Cloud, Spyro the Dragon, Crash Bandicoot: Warped, Unreal Tournament and the Serious Sam engine. Most modern 3D games use a combination of LOD rendering techniques, using different models for large structures and distance culling for environment details like grass and trees. The effect is sometimes still noticeable, for example when the player character flies over the virtual terrain or uses a sniper scope for long distance viewing. Especially grass and foliage will seem to pop-up when getting closer, also known as foliage culling. LOD can also be used to render fractal terrain in real time. Unreal Engine 5's Nanite system essentially implements level-of-detail within meshes instead of just objects as a whole. In the popular city building game Cities: Skylines, mods allow various degrees of LOD-ing. In GIS and 3D city modelling LOD is found in GIS and 3D city models as a similar concept. It indicates how thoroughly real-world features have been mapped and how much the model adheres to its real-world counterpart. Besides the geometric complexity, other metrics such as spatio-semantic coherence, resolution of the texture and attributes can be considered in the LOD of a model. The standard CityGML contains one of the most prominent LOD categorizations. The analogy of "LOD-ing" in GIS is referred to as generalization. Rendering and modeling software MeshLab an open source mesh processing tool that is able to accurately simplify 3D polygonal meshes. Polygon Cruncher a commercial software from Mootools that reduces the number of polygons of objects without changing their appearance. Simplygon a commercial mesh processing package for remeshing general input meshes into real-time renderable meshes. See also Progressive refinement Progressive meshes Sparse voxel octree Spatial resolution References Communications of the ACM, October 1976 Volume 19 Number 10. Pages 547–554. Hierarchical Geometric Models for Visible Surface Algorithms by James H. Clark, University of California at Santa Cruz. Digitalized scan is freely available at https://web.archive.org/web/20060910212907/http://accad.osu.edu/%7Ewaynec/history/PDFs/clark-vis-surface.pdf. Catmull E., A Subdivision Algorithm for Computer Display of Curved Surfaces. Tech. Rep. UTEC-CSc-74-133, University of Utah, Salt Lake City, Utah, Dec. 1 Ribelles, López, and Belmonte, "An Improved Discrete Level of Detail Model Through an Incremental Representation", 2010, Available at http://www3.uji.es/~ribelles/papers/2010-TPCG/tpcg10.pdf de Boer, W.H., Fast Terrain Rendering using Geometrical Mipmapping, in flipCode featured