In order to take full advantage of Mecanim’s humanoid animation system and retargeting, you need to have a rigged and skinned humanoid type mesh.
A character model is generally made up of polygons in a 3D package or converted to polygon or triangulated mesh, from a more complex mesh type before export.
A joint hierarchy or skeleton which defines the bones inside the mesh and their movement in relation to one another, must be created to control the movement of the character. The process for creating the joint hierarchy is known as rigging.
The mesh or skin must then be connected to the joint hierarchy in order to define which parts of the character mesh move when a given joint is animated. The process of connecting the skeleton to the mesh is known as skinning.
There are three main ways to obtain humanoid models for with the Mecanim Animation system:
Use a procedural character system or character generator such as Poser, Makehuman or Mixamo. Some of these systems will rig and skin your mesh (eg, Mixamo) while others will not. Furthermore, these methods may require that you reduce the number of polygons in your original mesh to make it suitable for use in Unity.
Purchase demo examples and character content from the Unity Asset Store.
Also, you can of course prepare your own character from scratch.
Unity imports a number of different generic and native 3D file formats. The format we recommend for exporting and verifying your model is FBX 2012 since it will allow you to: