How do I make a free form tail animation?

Question

I have a quadrupedal mechanical creature that has a tail. I like to make the tail animation natural or kind of adapt to the animation of the body but will return to its original transform when in idle like the ones below. I want to use this as a player in a game made with unity. I just want to mention that because it might be solved with unity instead. Not that I'm sure of.

I have the picture in pose mode but it's straight when in edit mode.

Any help is appreciated.

I'm sorry of the description is not clear. Please point out the things that is not clear so that I can edit the description.

Answer 1

Parent an UV-sphere to the dog (?...sorry) sized and positioned that way, that its "north pole" touches the end of the dog and its south pole is just a little further away from the dog as the tip of its tail. Or in other words: The diameter of the sphere is roughly a little longer than the dogs tail. Parent the sphere to the armature in object mode. Vertex parent an empty to the "south pole vertex" of the sphere. Attach an IK-solver to the tail and as target insert the empty. Adjust the chain length accordingly. Add a softbody simulation to the sphere. Make the north pole the goal for pinning the sphere at a stiffniss of "1". Play with the other parameters of the softbody simulation. By the way: When jumping around from one frame to a totally different frame the cache of the softbody simulation can get corrupted and blender not alway notice that ... which leads to very weird results or none at all. The easiest way to clear the cache is to set the number of the last stored from before the number of the first frame temporarily. Don't forget to set both values to the length of your animation at least.