rigging wrists for game characters
hey guys, I'm wondering if you have any thoughts about rigging the wrists up for game characters. When using biped I have the hand as a separate floating object that rolls inside a ball socket which is the end of the forarm. If you wanted it to be seamless, would you need to have another bone or something?
Replies
To position a biped hand you have to guess wildly while rotating and scaling the bicep and forearm bones, which just doesn't give anyone the precise control to align a biped hand into a ball socket.
It would be nice if biped hands broke off from the forearm but they don't.
It would also be nice if they could be positioned like CAT bones or regular bones in "Bone edit mode" where each bone can be placed independently and the scale isn't locked forcing the other bones in the hierarchy to move and shift.
You might want to select the biped hands, click Tools > Snapshot.
That way you copy the hands and their pivot positions but you can then turn them into reguar bones (Animation menu > Bone Tools > Bone Tools floater > Object Properties rollout > Bone On) That will make them easier to place and align without having to worry about the rest of the arm.
You can also use Animation > Bone Tools > Bone Edit Mode to place the pivot for each finger bone, something I really hate doing with biped and only using scale and rotation... grr...
thanks for the ideas!
in this case I'd use a dummy/point helper positioned exactly where i wanted the hand pivot and align the hand joint to it while scaling the forearm bone
I'm all in favour of building custom rigs but doing it properly is a big jump up from using biped and not a task to be taken lightly.
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Even if you use the align tool on the wrist to move its position to a point and the bicep and forearm scale allows you to get there, it won't match rotation. It also, throws your elbow out of whack. You spend a lot of time dancing around all 3 joints. Each time you tweak one it messes up the others, you keep refining it until it gets close enough, which just won't work for mechanical characters.
A little imprecision at the rigging stage almost always comes back to haunt you later when animating. In the case of a ball joint, its probably going to wobble unless its matches mathematically.
Other systems like CAT and bones, you just move the elbow and align each joint, it adjusts the scale of the bicep and forearm automatically.
I wouldn't personally use CAT, its too buggy and the IK setup is less user friendly, but it illustrates the point well. You don't need to go full on custom rig, just replace the hands with copies of the biped hands. After they are properly aligned, precisely, you can link them to the biped forearm and they behave like regular biped hands.
They could also solve the problem by allowing the hands to be "torn off" like you can do the spine, clavicles and the neck.
Yeah me too. I usually use expressions on that forearm joint. As I turn the wrist 100%, the forearm turns with it at 33% of the same rotation.
You can even go stretchy limbs if you really want to go nuts.
The way biped handles IK is different than standard IK. It's all handled on a single set of bones there aren't multiple rigs with blending and snapping. The system lets you drag the hand around and then rotate it by interacting with the exact same object, it's a great little system and one Naught Dog spent some time mimicking in Maya. With biped you stick the hands or the feet to world space or another object if you want, instead of a IK target and blending.
It's a bit hard to explain but once you use it, its kind of hard to go back to the old IK set up, which is my beef with CAT it uses the IK blending...
So does the industry rely on these automated rigs now? Or are these programs used for quick setups mainly?
http://tech-artists.org/forum/forumdisplay.php?f=11
Particularly, follow the links on this thread discussing wrist forearm twisting:
http://tech-artists.org/forum/showthread.php?t=1822
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Have you checked out the rigging dojo yet?
http://www.riggingdojo.com/live/broadcast-archive-rigging-dojo-live/
In the past studios using Maya would end up having to custom script or buy plug-ins that do all of that stuff.
HOWEVER Maya has humanIK now and its pretty awesome. It's like they took MotionBuilder and stuffed into Maya. So if you're a Maya user you should look into HumanIK, it has a few bugs and could use some more features but its pretty awesome and its better than trying to go it alone with bones and old school rigging techniques from the 90's.
(Biped's been around since max 2)
dproeder
It's standard practice to make use of things like biped/CAT/Puppetshop/and so on to drive your actual deformation rig. Keeping a layer of separation between the skinning and the animateable objects means you can chop and change whenever you need to as well.
Twists really prevent the volume loss when the forearm twists. It's constrained to an axis.
What that essentially breaks down to is: if you skin it to the hand bone, and you decide to BEND the hand at the wrist forward or back, half your forearm would bend with it.