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Level of Detail (LOD)

When a GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
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in the SceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
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is far away from the CameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
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, you can’t see very much detail, compared to when the GameObject is close to the Camera. And even though you can’t see the detail on a distant GameObject, Unity uses the same number of triangles to render it at both distances.

To optimize renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
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, you can use the Level Of Detail (LOD) technique. It allows you to reduce the number of triangles rendered for a GameObject as its distance from the Camera increases. You use several Meshes and optionally a Billboard AssetAn asset that is a collection of pre-rendered images of a more complicated Mesh intended for use with the Billboard Renderer, in order to render an object at some distance from a Camera at a lower level of detail (LOD) to save on rendering time. More info
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, which all represent the same GameObject with decreasing detail in the geometry. Each of the Meshes contains a Mesh RendererA mesh component that takes the geometry from the Mesh Filter and renders it at the position defined by the object’s Transform component. More info
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component and represents a ‘MeshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
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LOD level’, while the BillboardA textured 2D object that rotates as it, or the Camera, moves so that it always faces the Camera. See Billboard RendererRenders Billboard Assets, either from a pre-made Asset (exported from SpeedTree) or from a custom-created file that you create using a script at runtime or from a custom editor, for example. More info
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AssetAny media or data that can be used in your game or Project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file or an image. You can also create some asset types in Unity, such as an Animator Controller, an Audio Mixer or a Render Texture. More info
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has a Billboard Renderer component and represents a ‘Billboard LOD level’.

As long as your GameObjects aren’t all close to the Camera at the same time, LOD reduces the load on the hardware and improves the rendering performance.

Working with LOD levels

In Unity, you use the LOD GroupA component to manage level of detail (LOD) for GameObjects. More info
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component to set up LOD rendering for a GameObject. The images below demonstrate how the LOD levels change according to distance from the Camera.

Image 1: Camera at LOD 0 shows a large number of small triangles in the Mesh
Image 1: Camera at LOD 0 shows a large number of small triangles in the Mesh

Image 1 shows the first level, LOD 0. This level is the closest to the Camera, and therefore the most detailed LOD level. For example, many first-level LODs are active when the GameObject’s height fills 50% or more of the screen’s height.

Image 2: Camera at LOD 1 shows the Mesh with far fewer triangles and they are much larger in size
Image 2: Camera at LOD 1 shows the Mesh with far fewer triangles and they are much larger in size

Image 2 shows the next level, LOD 1. This level is farther away from the Camera, and therefore is a lower LOD level. For example, many LOD Groups use three levels, where LOD 1 is active when the GameObject fills between 25% and 49% of the screen height, and LOD 2 is active when the GameObject fills less than 25% of the screen height.

Because the arrangement of LOD levels depends on the target platform and available rendering performance, you can set maximum LOD levels and a Lod Bias Quality setting in Unity. The Lod Bias determines whether to favor higher or lower LOD levels at threshold distances.

Naming convention for importing Meshes

When you import a set of LOD Meshes, Unity automatically creates an LOD group for the GameObject with appropriate settings if you follow this naming convention:

  • Your set of Meshes have file names ending in _LOD and a number ranging from 0 to the total number of LOD levels minus one. For example, if the base name for your Mesh is Player, name your files Player_LOD0, Player_LOD1 and Player_LOD2 to generate a Player GameObject with three LOD levels.
  • Name the most detailed Mesh file _LOD0.
  • Make sure the rest of the Mesh file names increment corresponding to decreasing detail.
  • Set Billboard LOD levels to have the highest numerical prefix (because they always have the least detailed level).

You can use as many LOD levels as you need.

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