unity physics joint

除了unity文档（有点儿过于简略）之外，可以参考一下PhysX文档：

 

http://docs.nvidia.com/gameworks/content/gameworkslibrary/physx/guide/Manual/Joints.html#spherical-joint

 

http://docs.nvidia.com/gameworks/content/gameworkslibrary/physx/apireference/files/classPxJointLimitCone.html