Transforming Robot Production Pipeline Volume 6: Rigging

In this lesson, we will add knee controls. We're just about finished with our leg rig. We have the knees to build, and once were all finished up with that, we can rig the wheels connected to the shins. And then we can start to move up the body, rigging the spine and then the arms. And then we get to the vehicle, there won't be too much to rig. So let's get right to work and get the knee finished up. So after we create the control, in the next lesson, we're going to create a connect curve. That way we can always find the knee control. It's a very useful object to add, so we'll learn how to do that. But we have a few challenges with the robot's legs. You can see they're at a slant. So when we add our pole vector constraint, what's going to happen is our entire leg is going to shift to point at our knee control object. So we'll learn how to keep our rest pose while still maintaining our constraint. And another challenge is that the ankle, the way it's designed, we need to make sure that the knee will follow our leg control. That way we don't get any breakage around the ankle. And so we can stay true to the robot's design. All right, so let's get right to work. We'll use a script to build our knee control. Scripts do everything. Let's load in the script. We'll create a joint curve. So we'll find it-- here it is. So it's a curve that is the shape of a joint. And what we do is we create three NURB circles, stored in these variables here. And then we rotate the last two so that by the end of it, we have this joint-type shape. And then freeze transforms after we have rotated the last two curves, and then we take their shapes and parent them to our first curve. And then following that, we go in and delete the transform nodes that are left behind, and we rename the curve to jntcrv. Delete any history to clean it up. So let's highlight everything and add that to our shelf. We will rename this to our Joint Curve tool. OK. So we can use that the tool tip. That's descriptive enough. Now I'll label it jcrv. All right. So if we were to click on this, notice we have a curve. And it's very, very small. Let's increase its size. Much better. So we'll scale this up to a good size, easy to select. This should be pretty good. Let's now hide our robot. So we'll head over to the Show menu and hide polys. We can now grab our curve and snap it to our knee joint. All right, next, let's move this out. We won't worry about mirroring this just yet. We'll first make sure it's in place, meaning that it's constrained in a way where we don't lose this offset in our leg. So with it still selected, we can rename it two cc_lknee01, and we can color-code it. So moving over to the Attribute editor-- again, if it doesn't load, simply just reselect the object. It happens at times. But I'll now move to the first tab. And at that point, we'll choose the color of blue. All right. So it's color-coded. It's renamed. Now we need to worry about constraining this. So it's really quite simple. What we'll need to do is grab our thigh joint, and let's duplicate it. Ctrl-D. We'll create a new layer with the selected object, and we'll template it. All right. So now we can go ahead and constrain our IK handle pole vector channels to this object. So with the knee control selected, we'll grab our IK handle-- there it is-- and we'll pole vector constrain. All right, so you can see the offset. So no worries at all. We just need to now translate the control over so that our chain is right on top of the templated chain. Beautiful. All right. So once that's been taken care of, we no longer need the templated chain, so let's go to the brand new layer we made, right-click, and first, select all objects so we can delete them. And now at this point, we can right-click on the layer and choose Delete Layer. All right. So we're good to go. The curve is where it needs to be. Let's freeze its transforms. It's working just fine for us. And now we're ready to mirror it across, so it's let's use our mirror tool for that. We'll rename the curve and then apply another pole vector constraint. All right. So notice how the right leg also did not shift? So it's just a really neat trick for keeping our offset on a leg that has an irregular bend. All right. So now at this point, we can test things out. Our knee controls look good. I'd like to go to this control on the right side and color-code it to red. All right. Great. Now remember, we need to make sure that the knees will follow our leg control, so let's simply parent them, and that will take care of that. So you'll notice now when we grab our leg control and start to rotate it again, we won't have the ankle breaking on us at all. Beautiful. Let's test the right side. Looks great. But we still have control to create offsets in the knee if we need to. All right, wonderful. So let's say we stop the lesson, and we will clean up our leg rig in the next, create the knee connect curves. And then following that, we can start to rig our wheel and then move our way up the spine.