View Full Version : Animating Arms in IK: Pros & Cons

07 July 2008, 07:57 PM
For all the animators

Do you guys shy away for animating arms in IK?

Does the popping bother you, have you compensated for it or do you just IK arms 80% of the time.

07 July 2008, 08:51 PM
For me, it depends on the complexity of the scene and motion I need. Sometimes ik is fine, and others I do fk. Then too, we have the wonderful ability to use a slider and switch back and forth between the two, which is a great feature.

For very specific arm placement, breaking of joints, etc., fk is probably the only way to get what one wants.

As for popping, there shouldn't be any. So...maybe a rig needs adjusted as well as certain channel(s) locked out or rotational limits set. Remember too that different programs may favor a particular base pose or orientation(z direction) for the model for their bones and ik to be at optimum for the way the program works. That includes rotational position of the way hands are modeled, etc.


07 July 2008, 08:54 PM
What pose do you recommend, not the T pose..right???

07 July 2008, 09:20 PM
I use IK usually to block out the poses more quickly. When I got the poses and timing nailed down, I bake the IK to FK and continue working with FK.

In messiah there usually is no IK popping. Even if the hand moves over the shoulder, the twisting of the arm is a continuos movement, I think this is different from other programs. When setting up the arm, you should only take care that the first bone in the chain is zeroed out (i.e. you parent it to a pivot null).

Setting up the arms in a T pose is just fine. It only makes a difference for the deformations whether the arm is straight or bent, not for the IK.

07 July 2008, 09:33 PM
To get good rotational arcs you need to use fk. For example if you are wrokign on run or walk cycles I definetely suggest fk. Because ik generated motions does not show good arcs. Also it is easier to create follow throughs and overlaps with fk

07 July 2008, 09:36 PM
I animate arms in IK only when there's a reason to, such as if I want the character to hold his hand on the back of a chair, or if I want a character to hold an item in both hands.
Generally FK provides more natural interpolation and it's always very easy to see when arms have been animated with IK. The same goes for legs, I'll fade them to FK if the character is for instance hanging from his hands and I want them kicking freely instead of being planted on the ground.

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07 July 2008, 09:36 PM
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