Hey Brandon.
Let’s answer some questions about IK and FK.
Yep – IK is much easier when you need to have the end of the chain stick in place – like a Foot on the ground.
FK is easier for arms when they don’t interact with anything. Just walking along swinging by the side of the body = FK
But if the hand needs to be placed on a table or something like that. IK
FK gets you arcs for free, but it’s impossible to keep the end of the chain in the same world position if the rest is moving.
IK is way easier to place it exactly where it needs to be but it’s not without it’s cons.
It moves in a straight line, so it requires more attention to make it arc.
It will “pop” when it goes from straight to bent (or vice versa) – which requires more attention to control
(Side note: you might hear or something called “soft IK” that cushions the pop – however the animator still needs to compensate for this, so it is just a different flavour of the same problem for them – so I haven’t seen many rigs both with this anymore)
Switching:
Ideally you want to switch as little as possible. So it might be easier to do the whole shot in 1 mode if possible.
If you do need to switch it’s an extra thing you need to keep track of as an animator (and there’s already a lot of things)
I used to do this switch over 1 frame and then there was just that 1 frame pop you had to manage. This is what I have been teaching for years.
But then someone taught me that if you blend over 3 or 4 frames it’s way easier. And it’s true.
Match both FK and IK at the start and end of the transition – exactly where the limb needs to be. Then Blend from 1 to the other over 3 or 4 frames.
It is way easier and the results are seamless. (It only tool me 17 years to learn that trick)
Pole Target vs Leg Rotation (IK):
I prefer the pole target as you hardly need to touch it on the IK legs. But with the leg rotation method you have to pose it exactly where it should be on every key pose.
.
