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Can Someone Teach Me Blender IK?

Bloodsong Termagant

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   i've been working with 3d figures and rigging and animation for... decades, here.  but i can NOT get blender's IK to work for me in a way i understand.


   i come from poser, where using ik is dead easy


you load your figure, you turn off ik, you pose the arms, you pose the legs.

you turn on ik, THE POSE STAYS THE SAME.

you move the hands/feet to move the limbs (i do understand this is actually blender's 'targetless ik'), or you move the body and the limbs stay in place.

you turn off ik, THE POSE STAYS THE SAME*.

and everything is keyframed and comes out the way it looks.

(*: okay, often the hands would come out with ridiculous 1760 degree rotations or something, but that was a relatively minor fix.)



in blender, if i turn on ik and pose the rig, the limbs are not keyframed.  and if i import this animation to sl, the limbs just remain straight.

i've tried keying visual rotation, but that won't auto-key.

on top of everything, if i turn ik on, or i turn ik off after doing some posing, the pose completely changes.

now, avastar has functions to copy the pose to the ik rig, or to copy the pose to the fk rig.  which i try to use... but they only seem to work about 90% of the time, and only on the default human rig.  if i try to adjust the rig to make it work better for me, and for my model... it's out the window.



all the ik tutorials for blender that i've found are basically the same, and set up the ik the same way avastar has its ik set up.  basically, not useful if i want to set up my own custom ik.  which i must want to do, since the basic ik isn't working for me.  ???


i did have limited success with changing the avastar ik in this manner:

i used the ikWrist and the ikFootToePivot, and i set the ik chain to put the tip on the control handle.  (it drives me nuts when the wrist bone is right on top of the ik control handle.)

then i turned off the ik for the 'ankle' bone, and created it on the 'foot' bone.  i changed both ik chain lengths from 2 to 4 (foot, ankle, shin, thigh & wrist, forearm, shoulder, collar).

and lastly, i ended up deleting the pole controls, because omg, they are a pain!  and they wreck everything.


now when i moved the ik controls, the limbs moved with them reasonably.  when i moved the cog, the endpoints remained in place.

also, if i wanted to 'temporarily turn off ik to rotate a bone using fk,' i selected the control handle, then the bone with the action center set to 'active.'  that way, when i rotated, say, the thigh bone, the foot controller moved with the whole leg, like i'm used to.  as some inexplicable bonus, i didn't have to go back and convert any of the keyframes from ik to fk (and i have no idea why).

the bad news is... when i tried to append actions made this way to the default rig (i was working on a project created by another modeler/rigger), they totally blew up.  and, when i went to turn off the ik controls to polish off the animation keyframes... the ik and fk poses were decidedly different, so THAT didn't work.



basically, what i want is to be able to seamlessly switch between using Ik and using the regular FK rig, using custom settings of my choosing. or how to set up an ik rig that will do that.  or... what i really really want is the rigify tool as seen here: https://blender.stackexchange.com/questions/65290/how-can-i-seamless-switch-between-ik-fk

is there a way to surgically replace the avastar green pose bones with a rigify rig?  if i dont care about sliders?  is there a way to create a rigify meta-rig or something that will control the avastar green bones?

is there a way to autokey 'visual rotation' whenever a limb changes?  blender doesn't seem to recognize when the bones visually rotate.



you know, i THINK i understand how blender ik works.  i can grasp the target thing and the chain thing.  i even get the pole thing and the pole angle control whatever.  but i don't understand why it doesn't work right for me.


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again with the blender complaint principle.  as soon as i complain, it gets fixed.


or, in this case, i learn something... THAT HELPS!


    i started with this tentacle by dan pro, then added modifiers so that the (new) ik rig copied the rotations of the (original avastar) green (fk) rig, AND vice versa, but swapped influence based on the FK/IK slider. 

   it still only works to seamlessly switch between fk/ik if it's keyframed, and you have to manually keyframe all the parts each time...  but i dont have to muck around with rigify!!


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