Future of forward/inverse kinematics?


Hey all,

So something I’ve been thinking about for a while is the whole way that Maya & Softimage deal with forward and inverse kinematics. They pretty much force the user to think about which method they’re using at all times… which usually isn’t TOO big of an issue, but it can get daunting if you want to switch back and forth more than 2 or three times within a shot. And if you need to change your timing, it can get really really messy.

I was looking at how a package like Mirai handles fk/ik blending and it basically just has a skeleton that you animate pose to pose. You can lock down certain bits of the skeleton (feet, hands, torso, hips, etc), and move the rest of the body either with ik (grab a hand and move it), or fk (grab an arm and rotate it). You can even do an “inverse fk”… grab the foot and rotate the lower leg AROUND the heel, lifting the body (woah).

The trick is that you don’t have “animation curves” to deal with… you’re animating pose to pose. So you can’t really offset parts of the body w/out going and modifying the poses… it’s much more like stop motion or 2d animation. However, you never have to THINK about what you’re doing… if a hand is in the same spot in space for 2 poses, it’s an inverse kinematic solve. It’s very fast… seems very easy to use…

I’m wondering if anyone else thinks it might be great to have sometying like that in Maya. Think about how much easier it would be to rig up fingers and hands… you need to pin the tips of the fingers? fine. Pin 'em, move the hand. They stay where they’re supposed to. Need to move 'em with FK? no problem. rotate 'em. done. Have a character falling off a building and tumbling so you need to alternately pin the chest, then hips, then feet, then head, then chest, etc? easy. just pin 'em. done.

I think that this method of animating could really push maya to the next level… what are your opinions? (I’ve already logged this as a SUG through a|w, but I wanted to hear what others thought).


p.s. if you got some time, d/l http://www.animagicnet.no/AnimaniumDemoVideo.avi it’s Sega’s animation system… very much like Mirai’s.


Anything that would make animation easier would be great.


There is something about IK/FK blending in the Maya 5 “what’s new” PDF file.

Forward and Inverse Kinematics (FK and IK)
FK and IK are the backbone tools of character movement and the ability to work easily with both in the same character gives you more options. FK
is used for direct and precise control of individual joints in a character’s skeleton. IK allows for the manipulation of a series of joints with a single
control: the software calculates the movement of the rest of the joints. Thus, IK might be used to animate a character raising its hand over its head;
FK would be used to bend the elbow.

Maya 5 offers FK/IK blending: a highly requested feature that allows you to blend between animation applied directly to joints and animation
controlled through IK chains. Visible references to the full IK and FK positions during blending help you evaluate a sequence and create smooth
animation transitions.

I believe this is what you were talking about, Jason. Isn’t it?


Nope, maya’s fk/ik blending still requires you to know what you’re doing… and it doesn’t work on feet & hands. it’s fine for arms, but you can’t lock a hand down, or a finger, or a toe, or the ball of the foot and blend in and out of IK w/out setting up a complicated blending system… and w/out having the animator have to keep track of which “mode” they’re in.

The blending in 5.0 is better than it was in 4.5… which, in turn is better than 4.0 and previous versions… but it’s more like a patch on a problem, it’s not a true solution yet.



Originally posted by jschleifer
The blending in 5.0 is better than it was in 4.5… which, in turn is better than 4.0 and previous versions… but it’s more like a patch on a problem, it’s not a true solution yet.

Then We’ll have to wait till Maya 6 :rolleyes: :beer: :bounce:


Keep Animation Complicated!! MAKE US THINK!
That way it will be easier to keep jobs for us that have em. :stuck_out_tongue:

Seriosly though Id like to see something like that. Sounds like great fun to animate with.(even though the system right now is super fun too)
Thats a huge “added feature” that could sell maya like crazy!


Put your ideas here:



I wish there was a demo available for Mirai, so that I can play with it a bit to get a better idea of what you are talking about Jason, but from what I can deduce, what you are talking about sounds like the perfect solution…

Though I think it might be a while before we see anything like that in Maya :thumbsdow

O well…Maya 5 has enough new features to keep me busy for a while :slight_smile:


if anyone wants i could make a video of how it works and post it.
btw: jason. you can later decompose your animation into curves so you can fine tune it, but since mirai was never expanded upon the tools for managing the many curves you get upon decomposing :frowning: i had an idea that could make it a lot easier but they havent really been around much :frowning:


Heya Ambient-whisper,

a video would be great… this is something which I’d really love to see A|W understand, and I"m afraid w/out actually seeing it in progress, and seeing the difference between workflows, they might not decide to dedicate resources to it. It’d be fantastic to do a side by side comparison between animating with this method and animating with a standard kinematics method in maya.


I would love to see a video explaining this too! I have never used Maria so I can’t really visualize what you mean, but it sounds very very interesting.

Sounds like animating pose to pose in the trax editor a bit to me, but without having to worry about constraints or kinematics?


cool. ill make one soon. just gotta get a few things out of the way first. :slight_smile: i should have one as early as today. or tomorrow at the latest.

things i plan to cover.

1.) IK/FK posing. and the tools around it. ( pinning. IK scale/etc )
2.) the character module ( some rigging stuff, bone properties )
3.) some NLA stuff …self explanatory
4.) just some other misc tools :slight_smile:




I just watched that video, and I want it also. That system eliminates all counter animation. Im sitting here thinking about how amazing that method would be. No one would be needed to explain how the thing works. No Fcurves, no heavy technology. Even though, a pose managment system would be a good asset. (saving, recalling, blah blah blah) and I would like tangent control in and out of a pose.

man that thing is exciting.


@ mr. schleifer: couldn’t you just grab one of the maya engineers, put him in a headlock and give him a noogie until he agrees to put the features you want in? :thumbsup:

but seriously, how receptive is AW to these suggestions? they send reps around during beta testing, they have the virtual suggestion box and they listen to us at the trade shows but somewhere along the line it seems that all of these ideas are just tossed aside. i know that development is a long and painstaking process but where’s the overhaul that has been needed to some of maya’s features for the past several releases? and i don’t mean so much as an overhaul for most of the features but a refinement: for example trax is good, but not as good as it could be (as compared to say XSI’s nla editor).

@ambient-whisper: thanks for the offer, that’s very cool of you :buttrock:

-mental :surprised


For me that hits the nail on the head. I would love to see the video because i think you are talking about a system that works in a similar way to Marionette here (though i won’t discuss particulars for abvious reasons).

Frankly, anything that makes the process more transparent to me is a good one.
I love Maya but when you need to lock a hand down for six frames, fk it to the next pose and lock a finger down for 18 frames it is, mmmm, problematic.

Good luck.


I’d love to see it in Maya. I was lucky to get a demo of Mirai before the whole Nichimen/Wingededge/Izware whatever thing happened and loved it. I still peek at the site every once in a while wondering if Mirai will ever come back.


Hey ya’ll…Allow me to jump in.

The reason why I’m jumping into this thread is because here at cinegroupe we have developped a pretty user friendly FK/IK 1 frame switch at the click of a button(with the help of scripting of course) It is incredibly usefull and after seeing many FK/IK systems throughout the biz, I must say that ours is quite impressive. I like XSI for this reason. And it doesn’t bug out either, you just have to know what’s going on.

The whole mystery of IK-FK blending in is an interesting one and the whole ability to do so has come a long way for both Maya and XSI.

What jschleifer has been talking about Mirai having the ability of IK/FK but NOT having function curves sounds strikingly familiar to Character Studio’s BiPed technology. This system has been availabe on the market for the past 5 years I believe and is nothing new to the digital artist. The great engineers designing this system make the user believe IK/FK is at their finger tips. It’s just a question of changing your manip tool from rotate to translate, and then placing a key. However what’s going on in the arithematic behind the scenes is quite different. BiPed and Mirai do not use rotation coordinates. When you are saving a key you are saving the position in space(translation) and NOT the degree of rotation. So in reality, you ONLY have ik.

What I’m trying to say is that Mirai doesn’t realy have IK/FK, it just feels that way for the user. The reason there are keys and not function curves is because the poses are only recorded in translation.



so if you take an arm and frame 1 of your animation and have it pointing down, then go to frame 10 and have it pointing up, what type of interpolation do you get?



theres a bit more to it than just how its mapped. personally im after a setup that doesnt require me concentrating on what happens underneath when i use a certain form of posing. the tools for posing are just as important. for example… Ik scale ( doesnt scale bones ) for example lets you take a characters arm, and do something like reach for a certain point in space. you just pick a vertex and the joint will try to reach it regardless of axis. so you dont have to rotate viewport… translate arm/rotate… then tumble viewport again. .etc. you just pick a vertex ( joint ) and where you want to go.
things like FK symmetry are also useful. if i use left click on rotate one bone rotates. if i middle click on rotate however, the bone that i specified as a mirror will rotate the same number of degrees as the linked arm. i know jason started this thread only on IK and stuff. but i want my video to cover a wider range of Character tools that i find to be useful.

( btw. i dont animate much. but from a test i just made. when i moved the arm up 10 frames later it looked like it was an FK move. would kinda make sense… since when i decompose the channel into multiple curves i get FK rotations.

personally what I am after is something like this.

say i animate a characters leg inside the viewport. i use Ik or FK to pose it. i can then after placing a few keys turn on the curve for that joint and i will see a curve inside the viewport as i make it. i would then also be able to use spline like tools to edit the path of the spline. and do stuff like refine it… delete points… this would translate to Fcurves… but in 3d form. much like trajectories… but would happen more interactively… and syncd with my skeleton. so if i delete a key in the animation editor… i would see a vertex in the spline dissapear. stuff like that would be nice.

anyway:) still working on video :slight_smile: got a bunch done already :smiley:
itll cover stuff like morphs too. ( to illustrate a less supped up version of what was used on lotr :slight_smile:




here I found a tutorial from an animator, who developed a pose-to-pose-animation workflow.

http://www.keithlango.com --> Tutorial --> pose-to-pose

Check the comparsion-video on the bottom.
Also the Maya-to-Max renderkit (http://www.keithlango.com --> tools) is great.

This of course would still keep the IK/FK - switching-problem

Thanks to the tutorial autor !!!