This article by Antony Ward on the 3d World site offers some valid tips on creating LOD (level of detail) for your models. What Antony describes is a technique commonly used in games to reduce the number of polygons in a model when the camera moves away. This technique is supported in Second Life and it is required if you want to reduce the LI (land impact) of your model.
The article is generically aimed at Maya but most of the tips offered can be applied to all 3D modeling tools. If you are in doubt that anyone of the tips in the article may not apply to Second Life I recommend you ask for details in the Second Life Mesh Forum.
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