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Now when you're working with joints in a character, there are several ways that you may want to animate it and there are times when you want to animate it and actually fix points of the joint in place. And to do this use what's called Inverse Kinematics. So I am going to go ahead and just create a simple, simple joint. We're going to go into Animation > Joint Tool, and I am going to select create a simple joint. Now this is the main reason why I tend to draw drawing with a little bit of an angle to them.
So let me show you why I do this. Is we are going to go ahead and hit Enter, and I've created a simple joint chain. Now this could be an arm or leg and typically IK is used on what's called the legs. So if we wanted to animate this, at this point all we could do is animate it with rotation. So if I wanted to, let's say this is a leg, I could rotate it at the hip. I could rotate it at the knee. But if I wanted to, for example, bend the characters leg and keep the foot in place, I really can't do that.
I can't manipulate this with translation without all the joints moving in one direction. So right now it's only rotations, and that's what's called forward kinematics. So basically you start at the root and move forward. So, for example, let's go ahead and create a very simple situation here. Let's go ahead and create a simple sphere. Let's say I wanted the end of this to touch the sphere. Let's say I wanted the character to pick something up. So what I need to do is position this, and then I need to rotate this in order so that it actually touches the sphere.
I can't just grab the end and say here, touch the sphere. But I can do, using what's called inverse kinematics. So I am going to go ahead and undo my way out of this, and let's go ahead and set this up. So in order to set up IK, what we need is a joint chain, and then we create what's called an IK handle. So we go under Skeleton and we select IK Handle Tool. So go ahead and go to the top. So that's the start of my chain, and this is the end of my chain.
Now what it's done is it's created another little object here. So you can see here, I've got now my joints have changed the color which means they are under the control of something else, and I've got this little brown thing here at the bottom, and that's called an IK handle. You can see it right here. Now if I go into my Outliner, you can see now I've got my joints and I've got an IK Handle. Now what the IK Handle does is it takes control of that joint chain. So if I move this, now the joints always stretch between the beginning and end of that IK handle.
So now if I have that problem of I want to set the end of my chain wherever I want, I can do that very simply and this is great, particularly for the feet and legs of characters, but also really for any sort of mechanical object. Let's say you had a robot and you wanted to pick it up. You can very easily set up an IK handle to do that. So now I can place my foot basically anywhere I want. But there's still a little bit of a problem here in that my top joint is still free-floating. Now in some cases this might be the way you want this to work, but there are times when I want to take this and make sure that my bottom joint is locked.
So we can address this by going into the attributes of the IK handle. So select the IK handle, go into the Attribute Editor, and now we can see we have a number of attributes for the IK handle. First of all, it tells you what the start and end joint of the skeleton are, then it goes into what's called the IK Handle Attributes. What I'm looking for is called Stickiness. So when Stickiness is off, when I move this the whole assembly moves.
But when I select my IK handle and turns Stickiness on or make it sticky, now that joint is sticky and it doesn't move. So this is great. So now I can actually move both ends of the chain and both ends stick to where they want to go. So now there's also additional attributes here for my IK Solver and one of the most important ones is called IK Blend. Now there are times when you want to animate something using IK.
So, for example, let's say I'm walking a character. But there are also times when you want to revert back to forward kinematics or rotational control. So, for example, if I position this here and then I-- let's say a character wants to walk and then swim and when it's swimming you want to go back to rotations. So what you can do is you can actually turn it down by IK Blend and now the IK handle is basically turned off and I can rotate my joints now. So if I rotate my joints, I can basically turn this off. And this can be animated.
And as soon as it comes back on it snaps back. Now there are other types of parameters for this is as well. Such as how a joint will twist. That's if you have multiple joints. You can certainly use more than two joints in an IK chain and also another one called Spring Solver and that's for dynamics, which we won't be getting into. So let's go ahead and take our character and set him up with an the IK chain. So let's go ahead and open the scene. We have got Dog_17, which is our current dog.
And so now we have got these arms here and I can rotate the joints, but I can't move them with my IK chain. So all I have to do is go into my IK Handle tool, select my first joint and my last joint, and now I've got my arm set. Now I want my hand. So let's go into our Outliner here and see how this is all set up. I've got my handle here, but I want my hand or my glove of my character to control the handle.
Well the easiest thing to do is just to take that handle, drag it and create a hierarchy. So I am middle-clicking, dragging it above the left glove. So now when I select the left glove, the handle itself is underneath. So now by selecting that glove, moving the glove moves the arm. So those are some tips and tricks for using IK handles and as you can see, it's a great way to make sure your character's hands and feet stay where you want them to be placed.
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