This system is called 'ragdoll', you can achieve this either with GS Pro, or with Newton plugin(i'd recommend Newton). You have to build a skeleton made of physical entities, connected with joints, that is a copy of the model's bone structure, and then set the 'real' model's bones angles accordingly. Physical entities should be invisible, and 'real' body should be passable. I'm not good at explaining, so if you haven't understood something, just search the forum, it has been asked before
