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There is a second type of inverse kinematics that Maya provides and that's called Spline IK, and it works a little bit differently in that it constrains the shape of the IK chain, rather than just the position. We're going to start here with just a blank Maya scene, and lets just go ahead and show you how this works. I'm actually going to go into a side viewport, because it's probably easier to show you in a side viewport here, and we're just going to draw a very simple skeleton. We're going to use our Joint tool, and instead of just a straight skeleton, we're going to draw something that's a little bit more windy or curvy.
So I'm going to kind of draw this S-shape curve here, and then just hit Enter to finalize that. Now if I were to use a standard IK handle, it would just constrain the end points of this chain. So if I go into my IK Handle tool, click on the first joint and the last joint, well, the IK handle does work, but it's going to try and retain the shape of that joint. If we want to actually animate the shape of this, we can't do it using the standard IK handles.
So I'm going to go ahead and hit Delete on that handle, and we're going to create a new one. So we're going to go under Skeleton and choose IK Spline Handle Tool, let's go ahead and take a look at the option for this. Now we have number of options here, we're going to leave most of this at default, one is called Root on curve, and that's really where's the root of this joint chain sitting, do we want to auto parent it to a curve, do we want to automatically create a curve? Yes, we want do that and simplify a curve.
The next one is the number of spans, in other words, how detailed do you want the curve to be created? By default, it's at 1, but to show you this a little bit more precisely, I'm going to turn this up to 3, and then we're going to create the joint chain just like we did before. I am going to click on the first joint in the chain and the last joint in the chain, and let's go ahead and close this. Now we have an IK handle here, and if we want we can select this IK handle and if we go into our Move tool, you'll see that well it doesn't work. That's because this type of IK chain works very differently than the ones we were working with before. Let me show you how this works.
Probably the best way to see this is to go into the Outliner, so I'm going to go into my Outliner, and you'll see that I have my joint chain, just like we had before, I have an IK handle just like we had before, but I also have a separate curve. And this curve is actually now the controller of this IK chain. So in other words, the joints of this chain are constrained to follow this curve.
So if I want to manipulate the shape of the chain, I have to manipulate the shape of the curve. So if I right-click over the curve, I can go into control vertex mode and you'll see that we have a number of CVs for this curve. So I can select one of these and move it and as you can see, it's actually changing the shape of this IK chain. And you can see how this can be very, very handy for precisely controlling an object or shape. You can have the joints manipulate the mesh, say the tail of a character, a snake, really anything; a hose, and then the curve is controlling the joints.
Curve controls the joints which control the deformation. Because this is just a standard curve, we can use all sorts of tools to deform that curve. We can just manipulate the control vertices directly, or we can use things such as clusters, or blend shapes, to more precisely control this curve. Now another thing I want to show you is that when I manipulate this curve, the joints themselves maintain the same length.
So if I shorten this curve, you'll see that this joint kind of protrudes beyond the end of the curve. If I lengthen the curve, you'll see that the joints still stay the same length. Now this can be very important in character animation, because the tail of your character will always be the same length. You're not going to be stretching and squashing it, and this can be very important for realistic animation.
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