Ik/fk (3)

[curiouskit]

Hiya,
I've looked around at solutions used for Ik/Fk switching, and was wonder what the general best practice way of achieving a rig that when switched the bones don't jump around but find the position of the previous control state and go to that .... (hopefully that makes some sense).
Are there good books or online tutorials that someone can point me to, or suggestions? Any help would be greatly appreciated.

[joojaa]

Blending (dont switch form 0 to 1 or vice versa but do it under a afew frames). Ive seen rigs and done that can switch between ik annd fk and them move the bones in equal position. Initself this sis noit hard to achieve.

Yeah i know what prompted you guys to search this ist the mouse rig. (what he does is he shows the switching but not what it can blunder to in animation time).

However this has a problem, the dervate of the position is not accounted for in most cases... it would be possible to add this but its not often neccesery if the animator understands that he must match the speed himself. Even tough ive seen 4 succesfull production rigs that have this i dont purehartedly suggest it (2 of wich were mine). Its prone to problems that the blending solution does not have.

But yeah all you need to do is make either a a scriptjob and or expression to monotor this. Now both methods have their advantages, here i usualy prefeer a scripjob since the switching is usaly only done by the user. Now the tricky part here is to ensure proper keying, so remind your animators they must key at theese points. you could force a key but animators usualy consider that tacky and breaking the testing of poses.

Note by the way that its pretty easy to move form ik to fk, but the other way around is more problematic. Indeed there are situations whare fk just can do things the ik will NOT do. Infact one nasty problem occours whan the user wants to go fk, then decides not to and moves back to ik and hes possibly screwed all up, unless he does it by undoing.*

basicaly the step goes like this, monitor the change of the switch attribute by scriptjob, if change set the bones position or the ik efflectors position so that the bone is exactly in same place using mel.

Theres another problem yoou may encounter because fk can put in values ik cannot with motionblur in soem cases. This is a realy nasty one to fix transparently... offcourse doing it rendertime nou prob

• also pleas pelase advice the animator agains positioning in fk and convering the pose to ik for interpolation between poses.

[curiouskit]

Hiya,
Thanks for the suggestions. I have a few more questions...

What are the problematic results of non-blending ik/fk that you can think of when rendering out isn't an issue, since the bones are simply exported to an engine?

How well does ik/fk switching work when the animators use autokey and count on that to key everything

Are there any tutorials you would suggest? Have you made any tutorials?

Thanks!

[joojaa]

QUOTE(CuriousKit @ 01/17/06, 06:28 PM) [snapback]225224[/snapback]
What are the problematic results of non-blending ik/fk that you can think of when rendering out isn't an issue, since the bones are simply exported to an engine?

You will find this problem very same problem whan porting to the game eingene espacialy if you ever interpolate the stuff in yoru game eingene (wich you probably will), if you use euler angles for solutions, qats wont have this porblem.

Se a ik fk soulution only works in a 360 degree slice of rotation, while ik has no such restriction so you could easily turn the bone to 360 wich offcourse is same as 0, now if you only ever interpolate withing a slice like qats do you have no problem but if you interpolate in eulers 0 and 360 are two evry different things. so interpolating form 181 they would prduce 2 different results (quats would not handle the exact 180 very well either) the other counterclokwise while the other rotates clockwise.

Autokey is not a problem but i dont actualy know of many serious animators that use autokey more then here and there. Because setting keys manualy by hitting s is abetter workflow and usuauly animators thinkof what curves they want to key to keep their curves nice to work with.

[curiouskit]

Hiya,
Thanks, that makes perfect sense. I can see why having it interpolate a few frames instead of snapping would definitely be a better solution, with less problems.
As for Autokey I agree with you =).

Thanks =)

[joojaa]

Well thisway you get controll over how the mixture between works. It does not free you form the game eingenes problem offcourse but it fixes all problems relating to this inside maya and possible lienar export time becasue the user WOULD se this happening inside maya so heed usdesrtand that hes on the worng slice.*

Also its usualy easer to de a ease in thisway form how the ik moves in comparaison to how the fk moves. Their trajectories are still dofferent. So maching the two movements into on semless one is often easier thisway. ITmay seem like more work, but down the line theres usualy less keys involved (as the animator does not need to makte the animatins to fit), also does not need fixing after the fact wich is allways a hiuge pain.

less keys, less fixing needed = LESS OVERALL WORK.

Fooling the user into blindly thinking all works well while it does not is shooting you in the leg!

*lets face one thing here, theres lot of porblems with normals unsewed edges some interpolatiosn etc because the operator works with hes eyes rather than understandig what they do... se allmost 10% of all the rpobnlems on this board relate to this invisible yet totaly udnerstandable problem once your explained the invisibles.

So sometimes its better to expose the suer to the cold truuth

PS i assure you that if it was easy alias would have included this in their ik fk switch. Butthey didnt because most places use the interpolation.

[curiouskit]

Hiya,
Have you seen any tutorials or books that do a really solid ik/fk switch that you reccomend so I'm not trying to reinvent the wheel? I've seen some that use a bone set setup, one set is the skinned set, one is the ik set, and another is the fk set. We use point and orient constraints when doing our fk rigging and need to continue to do so. Is there some internal maya functionality that will allow this behaviour without loosing the seperate controller boxes for fk and ik?

Thanks!