Animating with IK and FK

what's up everybody welcome back to how to become an animator and on today's episode we are going to be talking about animating with FK ni ke controls usually means how to deal with the arms and legs of your character different ways to do it we're going to talk about the switching matching blending when to use AI K when to use FK pros and cons that kind of stuff so without further ado let's jump into Maya here I've got Jules he's an animation mentor rig and I've got him set to a low resolution just keep things fast my screen recording software is kind of making things Chuck what I want to talk about is FK ni K now what I've done is I've made sure his right is in AI K I'll go over that in a second his left is in FK what that stands for is inverse kinematics and forward kinematics I'm in referring to this as screen left and screen right so if I say the left I mean our left alright so on our left or screen left of the character I've set him to IKr inverse kinematics on the right FK forward kinematics so forward kinematics all that means is that when you move the arm if you want to change the pose you're going to move things forward down through the arm that's where the control system works so if I want to go to a pointing gesture and I'm at the shoulder I'll move the upper arm I'll bend the lower arm and I'll move the wrist and do the fingers so forward down through the arm think that as you're pointing forward now you can see the here so if I want to move that do that exist exactly the same thing I'll take his shoulder I'll raise it up a bit now here's a quick tip when you're posing an arm in FK which is a lot what I recommend is a lot of people just grab this and go for you know wherever they think okay that looks like he's pointing I don't recommend doing it that way you can but you could run into gimbal lock or other problems that you'll learn about later but basically what I recommend instead is go piece by piece each of these little rotational axes so say okay his arm is down it is side and then he raises it up and maybe it's a little too kind of squished in against his chest so we'll pull it out a bit bring it down but so I recommend going by each of these things and you can always tweak it but this is a little bit easier to know you know what's going on in the arm to get it where you want it and then after that you can kind of tweak it with the door but that's how I recommend doing it anyway so that's FK forward kinematics now if you go look at the other system you've got AI K which is where you grab the wrist control and if you do the same thing you don't you notice you don't have something for each piece of the arm you have you may have the shoulder still in there you should but depending on the rig you should have a hand control and maybe an elbow pivot that's what that is right there and so all you do here is you would move it to the pointing position it would rotate it and I'll do the force push again and then the last thing is you've got this elbow and you can aim the elbow with this guy so take this over here and figure figure out where you want that so and there's the same more or less the same gesture I would have left them both in place now that may have seemed a lot easier and it kind of was but there are pros and cons to using each of these systems and so don't just jump the gun and go oh well it was way fast to do I K I'm gonna do that for everything because again inverse kinematics I K inversely controlling the arm from the wrist back to the shoulder which is not how naturally our bodies work if you go to turn shoulder upper arm lower arm then wrist that's the order of overlapping action so forward that direction inverse back so pros and cons which one to use and not to use a quick story for you when I first started animation I decided that I can't was easier just to put the hand where I wanted it move the elbow I was done FK seems like a lot more work I'm trying to do that and I wasn't very fast either so I use thank you for everything it was fine a lot of my animations look pretty solid however since then I've learned a lot it's been a couple years now I recommend I mean some people use ik4 everything but very few people I highly recommend just from my experience using FK for pretty much everything so here are some really good do's and don'ts of when to use ika versus FK if you are doing a walk cycle and you've got the arms down and they're gonna be swinging it is a lot easier with FK because any kind of swinging motion anything with an arc a nice path FK is much easier because everything is rotational and it's very easy to get those arcs you know you move this thing and you're giving a perfect arc same thing here another arc because it's all rotational it's very natural or I K you have way more control just think about this if you put this down at the same spot and even now like you know that was easier before the point but that took longer doing it I K then I want to do FK that was one control so they're pretty solid now let's say you want to do an arc with the I K you gotta move it over here this and then you got to make sure what am I am i stretching too much how do how do you know how far to go you want that elbow to pop so you have a little bit more work here now say you're gonna have him swinging his arms well if you're an FK you just swing the arms maybe decide like okay like the forearm is dragging and this thing is dragging a bit you go from there and here you're like okay well I'll move this to approximately the same location that just trust me when I say anything with a narc you really don't want to be using hiking controls you know a lot less flexibility and you have to key more things so trust me when I say that when you do a walk cycle you want to be an FK anything with swinging motion arms you know someone waving something throwing something someone throwing the punch even you're probably gonna want it in FK because you want to get that nice smooth motion which is a lot easier to get when you can say that the arm starts from down here it was bent and whatever was happening with the wrist is also good they're really quick I'll just go ahead and throw in a fist this is a really great rig anyone's like whoa that was fast there's some really great stuff in this rate so the idea here is you know if I want to make him punch I have to do a couple of keys but the majority of it is handled by this rotation you know that's you know that's the basis of a punch right there it's gonna swing things are gonna be a little bit cleaner than this obviously but the main mechanics are very easy with that it's a little very clean smooth however if I come down here I can do something similar where I can say all right let me get that posed I have to rotate this guy it's not too bad I can go ahead and do a fist on here as well I'm gonna just you know show you really quick I'll set a key here I'll move over here and I'll set my final key like maybe he's gonna do the same type of deal he's gonna throw a hook all right I gotta tweet this over here I do have to rotate his hand separately and then I got to deal with the shoulder which is a separate key so I got actually key that at one really quick all right here I didn't deal with the shoulder I didn't do that on the other actually so that's fine you know I didn't do that great on either one but here's the problem two keys on the other system would have to do some kind of an arc on this system it doesn't it's a linear motion so what I'm going to get is just the hands floating to that location which is not what I want so I'm gonna have to sit here and add more keys to try and get it both translation and rotation I'm gonna have to get it to feel more our key which you know it's just gonna take way longer to do and to clean up and then what happens if you move the body because here's another thing when you move the body this is one of the pros and cons we're talking about swinging motions well I K the system over here this doesn't care what the body's doing it locks it in place which is fantastic when you want the hand to stay on something and not move because what happens is if I move this thing notice how one arm stays and one arm goes with him if you need him to you know you do a thing where he punches you know his hands are here maybe he throws a punch maybe he's like throwing a punch but he's also trying to dodge something else you know if I need to do that I'm gonna have him lean back to dodge well now I got a redo everything I've done on this hand you know fix this key little bit not stretched out but then I gotta go to every other key I go too far what's that first run nope too far again you can see that it's just it's a lot more work for these swinging motions you don't want to be using ikk for this type of stuff now I've just been talking up FK and kind of bashing I K but it's awesome and you need to know how to use that too it's just different so if you've got a scene where somebody is leaning on a counter or they're gonna grab you know a big heavy object or something you know let's just say you've got someone who is leaning against a wall let's go there do this on both sides visiting on the wall is what you've got if you have a character leaning in AI K it's very easy to say alright one hand just go ahead and rotate it you know you still got the posing stuff the same let's go ahead and just throw that there that's do the same thing here so I go this way to go from the other direction I go back arm back a little bit down twist it make sure to bend it on the way that does not break his arm make sure you keep that in mind so don't break his arm and then I twist it wrist so this is an example where it is actually a lot easier to be using AI K you just sit here forever trying to match it and then you have to hope that by the time you arrive here like yeah finally it's on the wall is that a natural pose in this case it would probably work but you know if the arm were all bent in a weird way cuz that's how you had to get it to stretch there then you have kind of a problem now there's a way to get around this and you can use AI K to pose it and then switch it back to FK I'll show you that in a second so let's say that these two things are closing in on them or let's you know let's just say he's pushing him out but there they go pushing them out so now we need to move his arms here zip it out I've got a little too far I'll just bring that back to his arms and stretching and I'll just move this back to match it's fine you can see it is really easy just go slide and if I needed to lock it to it that's also easy so if I want you won't want to follow the other that's another video constraints and parenting all that kind of stuff we'll talk about that another time but to lock something on you're probably gonna be using ok now for the other hand you see where I'm going with this this is gonna be a little bit tougher it's not too bad let's say he's now pushing with his fingertips pushed it now just kind of getting rid of it I'm go ahead and do this it's like alright not bad here's the trick though do the hand slide let's examine each one is he in the right spot that's pretty spot-on like let me let me add a little bit of resolution to this thing so we want his hand to stay in that square it doesn't stay in that square yeah in fact perfectly it doesn't move it literally looks like he is pushing that wall great how would the other one I'm just to make this look decent I'm gonna just go ahead and rotate his fingers like he's really pressing up against there his little tip deal with the fingers yeah when he's not touching so I let that one stay that there you go now it looks like there's some force being applied by his hand I didn't key that though so it's gonna look like that the beginning doesn't matter so again that one over there perfect let's see how this one works and let's go ahead and just add you know that's where his hand is currently contained let's see if he stays there he ends up there more or less but no you've got a lot of rotational values you got this guy this guy this guy and the shoulder you have a lot more stuff to kind of worry about and you just want these moving one direction but you've got all these rotations it can be done people do the time but this is one of those things words like okay okay is way easier to get this done and get it done right because look at the difference so again that's what I Keys great for it's really good for hand placement and locking it down on something so if you need a character to put their hand on something lean on it whatever and they're not gonna move it you want I K because that sucker is not going anywhere and that's great because even if he leans let's say you've got the same thing say you've got the same thing on both sides and I'll just go ahead and cheat this it doesn't matter and he goes to lean well one arm is gonna stay on the thing one does not now this is actually how the feet work almost I'm just percent of the time when you download a rig the feet probably have something that you can move and they move on inverse kinematics okay same thing he moved the feet instead of the hand because you want when he plants his foot that he's doing this little chicken dance tightrope walking thing you know he's gonna go you want the feet to stay put you can actually switch the legs in a lot of rigs to be ika rigs out to be FK sorry if I do that you can see the here now I've got a leg the foot some up here I've got the upper leg that is so you could go and do a whole whole thing here now he's you know now he's trying to balance on something but you'll notice that the same thing applies one leg goes with one does not now most of the time you want the feet on I K even though most the time you want the hands in FK some exceptions of this are maybe dancers things with legs flailing around spider-man you know where you know he's anchored by his webs or something else and its legs are swinging below anything remember was swinging or arcing dancers with swinging or arcing you may want to switch it to FK for that that thing if there are big arcs and swinging motions FK otherwise lock it down go I K now quickly let's talk about how to get between them that depends on the rig a lot of the time so with the animation mentor characters and a lot of other characters you look for these little balls floating off the hand and you look in the control section you'll see some kind of some kind of FK snapping switcher or something like this so right now this arm is in AI K some rigs have something amazing called snapping which basically just means if you have this current pose and you really like this shape you just love this as it is you know this flow if I take this and switch it from FK to I K it's gonna take what I have currently an FK and make the I K version match exactly what I have that way I can continue animating without having the hand jump to some other pose so if I go to I K it stays put and I'm in the other system some rigs don't do this that's gonna be really helpful for if you need to do that kind of thing where you've got the big wall on one side switch it to AI K go ahead and place it wherever you want it and let's just pretend this looks good let's just say that that's him leaning on the thing but for whatever reason you need this to be an FK he's about to swing out of it well I can just switch it that little dot from I K to FK and now I'm in the other system I didn't have to take the time to pose it so that can be really helpful you just have to keep track of which one you're in and don't mix it up and that wraps it up for AI KN FK if there's anything else that you're wondering about questions it didn't quite get answered or there's anything else you want to see lose it in the comments down below but through that let's see if I missed anything if this video helped you out you learn something new hit the like button if you know someone else who could probably use this send it to them and if you want to see more content like this don't forget to subscribe thanks for watching I'll see you next time

Channel: Sir Wade Neistadt

Views: 124,509

Rating: 4.9627204 out of 5

Keywords: 3d animation, character animation, how to be an animator, animation interview, how to animate, animation ik fk, inverse kinematics, forward kinematics, maya ik fk, animating arms, parent constraints, character hand constraint, hand posing, dreamworks animator, animating in maya, animating in blender, how to get an animation job, animschool, animation mentor, ianimate, fighting animation, animation intern, animation lesson, animation tutorial, animator q&a

Id: p6PYKyxR0aY

Length: 17min 4sec (1024 seconds)

Published: Sun Dec 03 2017