IK FK blending confusion

I am confuse i am tryiong to do a IK FK rig and have watch and read several tutorials where you make 3 set of bones for the arms where one set is the IK the 2nd set is the deformer and 3rd set if FK by constraining the bones with copy rotation or copy location end setting up a driver but the end result is the same as taking the IK influence slider and putting it to 0 why go old the trouble of making so many bones to acheive the same results, i would like to know if there is a seamless transition to IK FK without the bone returning to original position

It can be done with two arms, but the easiest and the one which hits the least problems is with three. The basic principle is that you have a “real” arm with no human controls. Then, you have an IK arm (with IK controls) and an FK arm (with FK controls). The constraints in the “real” arm just get it to copyrotation in order to match whichever of the other two it is supposed to be imitating (whether the switch be IK or FK).

As far as smoothness goes, the above gives you two different arm positions and using the switch makes the real arm glide from one (e.g. IK position) to the other (e.g. FK position). It is possible to write scripts etc so that when the switch is activated, the “next arm” moves around to match the first, but these scripts can be problematic. If you’re going to key a switch change, then you may as well just line the arms up (the one not yet being used) just a few frames before the switch - it’s not hard. Also, if you make the switch change over a number of frames, (e.g. more than 10) instead of sudden, you don’t get a noticeable in-between arm pop like what happens when the switch occurs over two frames.

[quote=Lancer;1667561]It can be done with two arms, but the easiest and the one which hits the least problems is with three. The basic principle is that you have a “real” arm with no human controls. Then, you have an IK arm (with IK controls) and an FK arm (with FK controls). The constraints in the “real” arm just get it to copyrotation in order to match whichever of the other two it is supposed to be imitating (whether the switch be IK or FK).

I understand that part but isnt the real arm with no control already FK why woud i need an extra set of bones to copy rotation if when i lower the slider on on the IK influence the real; arm which is the deforming arm it will return to FK mode the same way that if it was contrain to a set of bones with FK, what i am trying to get is a seamless transition that i dont seen to get by riging 3 set of bones that when i transition the arm moves

You can, but any FK movement would then offset the IK version, so they usually end up fighting each other. It’s far simpler to have the neutral arm in rested position, moving to the other arms as constraints.

thanks lancer for your reply even that i dont get your point yet do yoiu know of any links to a good totorial in this topic 3 bone set up for IK FK blending? I was able to find a solution with maleficos macoyo rig which you have FK IK seamlessly but the pole targets dont seen to work for elbow movements i would like to see other peoples technics

Here’s a thread where we talk about fk/ik switching a bit and FGC comments on why to not just simply turn off the ik constraint (this is how I did it until he corrected me).
http://blenderartists.org/forum/showthread.php?t=179612
Now I use 2 sets arm bones, the ik set and the fk set. The fk set copies the ik’s rotation when switching from fk to ik. 3 sets of bones are fine too and there are advantages to them, normal 3 bone set would be fk bones, ik bones, and deformer bones so you always know which bones are weight painted - the deformers.

Personally, I use ik to animate everything and I’ve questioned the need for fk controls, some say you get smoother arcs while using fk… and it does allow you more precise control over a character.

I haven’t played with the macoyo rig, but I think Kiopaa’s Pantin character uses seemless fk/ik switching and used the same techinques, but improved on them a bit… It’s a python script, so you would need to know a bit of that to use it on your character.

Randy

REVOLT_RANDY thanks for the link i myself dont see the use of FK that u ca not do with IK i guess some motions like having an arm rest on a table and just have to animate the forearm would be better doing it in FK which is more circular in motion but i read that 75% of animators use FK for animating i just wonder why
i am just trying to learn how to rig like they brig in a commercial pipeline