Ultimate LOD System is a complete LOD based optimization solution for your project! You can generate LODs from your original meshes, or just generate Simplified versions of them.
Ultimate LOD System provide an alternative LOD mechanism more customizable, optimized, automatic and easier compared to the Unity "LOD Group".
Furthermore, this tool allows you to automatically generate LODs or Simplified versions from your original meshes, and save it. This tool was designed to work In-Game, Runtime or In-Editor.
With this tool, you just need to scan the meshes you want to generate the LODs in your scene and then the tool will render the LODs according to the distance between the meshes and the camera that renders them.