【Level Of Detail】
LOD0离摄像机最近，LODN离摄像机最远。LOD Group组件的用法是，将此组件挂在根节点上，然后每一个LOD挂同样多的Renderer(通常是子对象)。
At this point the empty object should contain both versions of the mesh and "know" which mesh to show depending on how far away the camera is.
按上述设置完毕后，这个空对象就知道距离Camera多过远的时候该用哪个Mesh了。
The percentages in the LOD bars represent the fraction of the bounding box height relative to screen height where that LOD level becomes active.
【LOD Bias】
LOD Bias，Edit -> Project Setting -> Quality 中可以设置：
【MaximumLOD level】
Models which have a LOD below the MaximumLOD level will not be used and omitted from the build (which will save storage and memory space). Unity will use the smallest LOD value from all the MaximumLOD values linked with the quality settings for the target platform. If an LOD level is included then models from that LODGroup will be included in the build and always loaded at runtime for that LODGroup, regardless of the quality setting being used. As an example, if LOD level 0 is used in any quality setting then all the LOD levels will be included in the build and all the referenced models loaded at runtime.
[Auto create LODGroup]
In order to simplify setup of LODs, Unity has a naming convention for models that are being imported.
Simply create your meshes in your modelling tool with names ending with _LOD0, _LOD1, _LOD2, etc., and the LOD group with appropriate settings will be created for you.
Note that the convention assumes that the LOD 0 is the highest resolution model.
[Shader LOD-Value]
Shader Level of Detail (LOD) works by only using shaders or subshaders that have their LOD value less than a given number.
By default, allowed LOD level is infinite, that is, all shaders that are supported by the user’s hardware can be used.
However, in some cases you might want to drop shader details, even if the hardware can support them. For example, some cheap graphics cards might support all the features, but are too slow to use them. So you may want to not use parallax normal mapping on them.
Built-in shaders in Unity have their LODs set up this way:
The idea with shader LODs is that it enables you to enable/disable various graphical features:
- Each shader has an LOD
- You can specify that shaders above a particular LOD will be disabled
参考：
1、http://game.ceeger.com/Manual/LevelOfDetail.html
3、http://answers.unity3d.com/questions/330839/what-does-the-lod-value-for-shaders-represent.html
