Hi Simon, I'm surprised that no one has responded yet. You've got a couple of subjects here. Carrara does have nice IK and constraint features. I personally prefer them to Poser's simply because of work flow in Carrara. You can key frame IK motion. As for subject A hitting subject B and subject B falling, Carrara does not provide for that level of dynamic, multi-character IK/physics interactions. Carrara does have physics but it doesn't function at a multi-IK chain level like that. Mark