Adding legs to a rig
Video: Adding legs to a rigAs we have already seen, CAT has a variety of tools that can speed up the rigging process. The most obvious of which are the preset rig types. Even when we need to create a custom rig, CAT still makes it possible to work very quickly. Let's take a look in this video at creating a hind limb for our creature. In a typical rig building workflow, we would usually need to create a number of bone objects, link them together correctly in a hierarchy, and then create an IK chain that would correctly solve the movement of the limb.
- What's next?
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Discover an alternative to the traditional character rigging workflow with the Character Animation Toolkit (CAT) for 3ds Max, which offers preset character rigs as well as custom tools for creating a rig from scratch. Author Joel Bradley demonstrates animation layers; CAT muscles, which you can use to create a skin that deforms and stretches realistically as your character moves; and the forward/inverse kinematics workflow. The final chapter puts all these features into motion, as you apply the tools to a full character rig with secondary bones and perform a stress test animation.
- What is CAT?
- Using and editing preset rigs
- Repositioning bone pivots
- Using CAT control gizmos
- Working with spines
- Adding limbs to a character
- Working with adjustment and motion layers
- Animating with the foot pivot system
- Building a start-to-finish rig with CAT
Adding legs to a rig
As we have already seen, CAT has a variety of tools that can speed up the rigging process. The most obvious of which are the preset rig types. Even when we need to create a custom rig, CAT still makes it possible to work very quickly. Let's take a look in this video at creating a hind limb for our creature. In a typical rig building workflow, we would usually need to create a number of bone objects, link them together correctly in a hierarchy, and then create an IK chain that would correctly solve the movement of the limb.
All of that could take a while to accomplish, depending of course upon our skill level. Let's see how long it takes us to get all of that done in CAT. Having already created a pelvis hub, let's make sure it's selected in our scene and then come into the Modify panel. All we need to do here is come down to the bottom and click the Add Leg button. As you can see, CAT creates an inverse kinematic chain that consists of a three-bone hierarchy and a Helper which you set at the base of the leg.
You may wonder why I am only creating one leg. Well, the answer to this question will become apparent in a little while, but before we move on, I just want to change my leg bone's color. So I'm going to click the color swatch and give it an RGB value of 28, 28, and 177, and just click OK. As you would expect with CAT, the number of bones in this chain can very easily be increased or even decreased so as to suit the character design we are working with.
Obviously, a value of 2 suits us quite nicely. As we demonstrated with the preset rigs, we can select any of the bones and adjust their position simply by clicking and dragging on them. A quick workflow tip would be to put the ankle in place first. This is so that as we adjust the length, we don't disturb the position of our knee. With our ankle placed first, we can then easily work our way up the hierarchy.
I'm quite happy with the position of my ankle bone, but I'm just going to adjust its orientation using the Rotate tool. Let's come over to the Modify panel and adjust its Length ever so slightly, again, just to better fit our character artwork. Now I can follow the same process and move on to positioning the lower leg and finally the upper leg. Once these are in place, I can come over to the Modify panel and adjust the size parameters.
So I'm going to do this on the selected bone first of all, and then I'm just going to reselect the lower leg and perform the same operations. I mentioned earlier that we were creating only a single leg for a reason. This was because once we have edited a limb, CAT assumes that we would like to place a replica of this limb on the opposite side of the rig. Coming back to our hub, if we come down and click the Add Leg button one more time, you will notice a create select on the opposite side of the rig with the exact same settings as our first leg.
This is a nice piece of functionality that can save us quite a bit of setup time. I'm just going to adjust the color of this bone as well. I'm going to scroll to the top of my Modify panel and click the Color Swatch, and set its RGB values to 6, 133, and 6, and click OK. Again, you'll probably recognize I am using standard biped colors. Typically, we would probably find ourselves adding two legs to a hub or pelvis as we have done here, but CAT certainly doesn't limit us to just that.
In fact, if you check out the preset rigs, you will find the Crab and Spider rigs that demonstrate the use of more than just two legs per hub. Let's continue the construction of our creature rig in a logical fashion and move on to adding a spine to our CATRig.
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