IK or FK!?

[goosh]

FK

Unless you want to grab something or carry a box or push off a wall, etc...

G

[gmask]

Originally posted by goosh
FK

Unless you want to grab something or carry a box or push off a wall, etc...

G

What he said. In most cases you really should rig a character so that it can use either.

[Joril]

I'd say IK.
Use a goal at the pulse to guide the arm, like any normal IK chain.
Then rotate the upper-arm-bone to point the elbow in the direction you want - pretty standard really.
You might want to guide the elbow with an additional goal in the IK chain, but it's quite a obstructive(hope that's a word) to animate with extra goals in a chain (or at least, in LW it is).

But then again, "All FK" just scares me :surprised

[ed209]

I've used both IK and FK rigs in a production environment. 90% of the time I'm working in FK unless I have to plant my hands. It's just such a pain in the butt to get good secondary motion with IK.

[Namroth]

With FK you can get nice arc eazy....

[steverage]

Yeah, Im still sure FK is the way forward! Also, does anyone use a small extra bone to act as a wrist or do you just rotate the forearm?

[adavies]

FK DEFINITELY! ik is pants for just about everything other than when the hand touches something

[Pinoy McGee]

I don't think there's a hard and fast rule re: IK or FK in arms. What it comes down to (in a production level) is the quality of the arm rigging, ease of use in posing, and how much control you require (or how fast a viewport feedback you want). If you can switch between types the better.

For example, when I'm animating a human biped run I prefer FK to pose the arms because I have better control doing it. But if I were to hand key a kung fu staff kata, a la Kilik in Soul Calibur, I'll need IK for the hand grips and release actions.

Same with the feet. Most of the time characters are on the ground and you want to minimize unnecessary feet sliding when walking or moving into a stance. IK constraints are great with this. But if you need to animate high flying, high kicking crouching tigers (with 720 degree body spin knockbacks!!!) you'll probably need more FK to pose the limbs and get strong silhouettes.

[adavies]

you can't do all that with IK legs? you wimp ;)

[MosaFacku]

i like to use both, but i tend to favor IK a lot more than FK. i just like being able to place the hand directly where i want it, not having to position the shoulder, then forearm. also, its not that hard to get good arcs out of IK, just place at least one inbetween in where u want the max point of the the arc to be, adjust your curves, and boom, nice arc in under 5 seconds.

[adavies]

I've found IK to be an ABSOLUTE PAIN when doing arcs! trying to maitain a nice arc whilst making sure you've got nice overlapping action between the upper and lower segments of the arm is a waste of time when you can make sure you get all that with FK in no time at all. i've found that you have hardly any control over the re;ationship between the upper and lower arm when you animate with IK, you only have the twist which is ok for the elbow (ish) but what about the forward swing of the arm? you place your hand where you want it in your arc, you are happy with that, but then you look at the upper arm and lower arm and maybe you want the angle between then to be a little more or less, you're going to have to move the hand again either up or down to correct that, which means you've just messed up you're lovely swing again, and so on and so on. i just find i am constantly fighting with the rig when doing swings and stuff. don't get me wrong though, IK is kinda nice when you have to come into comtact with something ;)

[westmeadow]

Ok, noob here trying to learn rigging aswell as animation!! uummm... lil confused. With FK, you just pick and rotate each bone in the arm to get the desired pose?!?! am i right? While reading Joril's post i go a lil bit confused (so like me). I now think that Joril was talking about the setup shown here in the middle But when i originally read it, i thought joril meant like the 3rd image shown, you control the point at the elbow to give the direction of the upper arm, and you just rotate the forearm after this, follwed by the hand etc. Would this work??

Arm Setup (http://members.lycos.co.uk/arronwestley/armsetup.gif)

Thanks for listening!

Assie :bounce:

[MosaFacku]

adavies, have u tried using a pole vector constraint to control the elbow? it usually works great for me. the twist channel is a constant pain since it causes the elbow to flip out on me 90% of the time. of course, if you're not using maya, then i can't really help ya. ;)

[adavies]

yeah, i'm using maya and pole vector/twist only affect the position of the elbow - they dont affect the angle between the upper and lower arm. the only way you can get that is by moving the hand, so you have to try and get a nice arc whilst looking at the angle between upper and lower arm to make sure it's not going crazy. why not just use FK?

[Dan Wade]

I am about to do an arm wrestling scene. Both hands will be gripping....so it seems IK is needed. Any ideas?

Dan.

[benjii19]

Have the spine unaffected by IK, place a null at the wrist and have the forearm controlled by Ik on heading and all 3 channels for the bicep, and have the wrist bone goal object as the wrist null. Maybe try using IKFK blending, u can get IK blender off the net somewhere if ur using L'wave. I had probs with IKFK tho for some reason the first time I tried it it worked then I rigged the character again and it doesnt work. Why I dunno?! Hope this helps. If u already knew sorry.


Ben

[Dan Wade]

Ah, that great dude, cheers. I am actualy using Softimage XSI, which i hear has a very good IK/FK system and blending options.

Only the arms will be in shot, so no need for the body or shoulder. Still hard though. I am currently looking into muscle deformation. 1 thing is still troubling me though. When the arm is on a table...most of the animation is driven from the elbow and not the shoulder.

Dan.

[benjii19]

It's nice to have been of some help, I have gone into muscle deformations with muscle bones and stuff I think they might be a bitch to set up and get in the way when animating, I have only ever used weightmaps for deformations, not got one 100% right yet. Dunno abpout ur table and arm prob tho.

Ben

[benjii19]

I mean i havent used muscle bones, bit of a typo up there

[Dan Wade]

The muscle system ive got working on XSI is quite good, and quite simple for what it does. Plus i can write very simple link with scripts, which is similar to driven keys in maya. So if the arm bend in a certain way...the muscle system will kick in.

Dan.

[LucentDreams]

coming from a classical background, anything that can get my character into the poses I want is good enough for me, I persoanlly prefer a rig that can switch and have been really studying how to set this up.

[grury]

Sorry if this is a bit off topic...
Does anyone know if it is possible to switch from IK to FK on the hands of IK Joe rig.

Cheers

[bentllama]

IK

i tend to only use FK for certain situations...I have just gotten =so used to IK that I can get the arcs of motion I want from them

[bentllama]

Originally posted by Kaiskai
coming from a classical background, anything that can get my character into the poses I want is good enough for me

i second that.

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