I have been wondering about this for a while - If you have a standard mesh of a human and it is rigged; how do you then edit that mesh whilst it is moving. For example if I wanted the man to grow an extra arm which I had full control over whilst the man is continuing a full walk cycle, how would I do that? The only solutions I can find are ways of disguising the swap between two pre-made models, no fluent transitions between the two.

I have asked several people and they often mention things like blend shapes but I was hoping to get a more specific answer.

Thanks in advance