FK/ IK switching

  • So, when doing animation in poser, swapping between fk and ik is very hard. (for anyone unaware it basically sets the entire animation to the new mode leading to interpolation of an unwanted manner). My current workaround is to bake the keyframes of a joint up until the swap (so if i were to disable ik for left leg, bake hip, left thigh, left shin, left foot). The only issue I have with this is it can make cleaning up said animation very difficult (if I have to simultaneously swap every limb for ik to fk i have to bake also every major bone).
    I was wondering if there were other workarounds other people have that are easier? I've tried messing around with controllers once or twice but it didn't go so well.
    (Poser 11 standard so no pro hax please :))

  • @pip.jr
    What do you mean by baking? DO you mean set keyframes on every frame for the various body parts?
    There is no need to bake anything... if you set your poses correctly you can switch between IK & FK without messing anything up... assuming you turn limits off before disengaging IK. No need to turn limits off when you go from FK to IK.

  • That is what I mean by baking, but i dont understand what your saying
    If I have these poses (i did these literally in under a minute just to try out so they are terrible)
    (I posed the first two in IK, then disabled IK on the right leg for the third)
    If I now play this animation, the right foot moves between the first 2 poses:

  • @pip.jr

    If I now play this animation, the right foot moves between the first 2 poses:

    Then it sounds like you are talking about interpolation between the key frames. ???

  • @krios Well... yes, but thats unavoidable?
    I want it to interpolate, but I can't set it to constant (as then it will just snap between positions). Spline results in the greatest issues but linear still has the issue above. Or are you suggesting I keep everything IK in playback?

  • @pip.jr
    That's kinda how animation works, you do need the smooth splines in the end.
    You can animate a walk without using IK in the end. But to set it up, it's a combination of both IK/FK. The point is that if your poses are correct, yu can turn IK off and the feet will do exactly as they should. No time now, but I can show you my workflow which might give you some ideas to start figuring out your own workflow.

  • Check this simple clip out


    This was animated almost entirely with FK. The only time IK was turned on, was to adjust the hip without messing up the feet, but again, most of the work was done in FK. IK is only a tool to keep things in place or to rough out an animation "carelessly". To do the final pass, the animation needs to work in FK or at least be finalized in FK to look smooth and natural.

    If you'd like to learn more about the way this was animated, check out Fbs7's [ post ]
    But please keep in mind that every animator has a unique style of workflow. What might work for one will not work for another.

  • But surely you want to keep things in place? I've always done my walks with the feet in IK because feet should stay still on the floor in a walk?

  • @pip.jr actually, it's the toes that should be, but typically aren't, the end of the IK chain, for a barefoot walk, as @krios ' animation shows.

  • Well, but then my point still applies just using toes rather than feet?

  • @pip-jr
    Again, it's a combination of IK/FK, and not only at the beginning or end of the workflow, but even when setting up the passing position, where it is handy to lock the foot that is stationary while adjusting the hip. But then you take IK off and test the pose to make sure there are no odd twists & bends.

    This particular way of animating a walk is based on the teachings of Richard Williams:

    image copyright: Richard Williams

    Basically: You first create the contacts, then a passing pose between them and then the down and up pose between those 3.
    If you do your poses correctly, Poser will need very little adjusting between the key frames in both, IK & FK modes.

    IK is not only a cheat, but it's "unnatural"--people's feet do not get nailed to the floor with every step. This "nailed" feel is very apparent with Maya, which has a perfect IK system, and the feet tend to stay in place a lot better then in Poser.

    Useful reference

    Good point. Might have to pay more attention to the toes instead of the heels.

  • Hello Pip,

    Here's a process for setting up walking with FK while preventing feet slip.

    link text

    You can switch from contrained feed to unconstrained feed, change walk speed and walk styles, and adjust end points. It's somewhat limited to moving in straight lines and turns, though... it would be hard to build a graceful walk in a curve that way, or to do a dance.

  • Now, let me offer you some ideas about switching back and forth with IK/FK. You can do that, as long as you move back to IK. You don't actually need to keyframe every frame - that's a lot of work.

    Consider this straight IK animation. It only has 4 keys (plus 2 incidentals for the little hand push), and both the hands and the ball are perfectly linear interp; both hands are IK on:


    makes this:

  • Now I say: "let's get some curves going on that right hand!!!"... then I switch off IK in both hands; I don't touch right hand between frames 1-10 and 30-40 (as it's in contact with the ball), and I don't touch frames left hand between frames 10 and 30 (as it's in contact with the ball), as I don't want to screw the IK interpolation.

    So I work the right hand between frames 11 and 29, and I leave left hand alone (as this is just a fast example and i'm very lazy by nature). I'm in FK mode, so I work rotations. I get a couple of extra keyframes after 12 to get some little rotations in place; at this point you can actually do anything in FK with the left hand, as it's out of contact with the ball ==> AS LONG as you return it as it was on frame 30


    getting this animation in FK mode:

  • But now I say "Holy Buritos!!!! Now the hands are not tracking the ball!! Then hands are gettihng inside the ball, out of the ball, it's complete ruin!!!".

    Not so much. Just put back IK on in both hands, and now the hands will track down the ball again. And, because of Poser magic now the rotations added to upper and lower arms are recalculated as new IK-based hand positions at frames 14 and 17.

    Then the thing is once again in IK mode, and the hands are tracking the ball once more. So I decide to add the best thing you can do with IK mode, which is hip movements. I still have exactly the same number of keys before (7 keys in total: 4 main position keys and 3 incidentals for hand/arm pushups). So I get this in IK mode:

    Notice that while the hip is doing its jabberwocking up and down, and the right hand is doing some rotations while not in contact, the ball is still in a perfectly linear path and the hands keep tracking it perfectly on the same linear path while they are in contact.

    So, switching between IK and FK is really fine. Be aware, though, that they is a bug when moving out of IK mode; sometimes it calculates crazy rotations; that's a nasty bug around for many many years; if you move out of IK mode and get crazy rotations, you'll have to clean them up (just remove the crazy angles and let it do the linear thingie there).