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When you create a basic armature, the bones manipulate the character by rotating, and this is called forward kinematics. But there are times when you'll need inverse kinematics, which will stick a bone to an actual object or position in the scene. This is particularly useful in the feet of the character. You want the feet to stay planted on the ground, but you may want to move the hips of the character or the rest of the character around to position them above the feet. So let's take a quick look at how to set up inverse kinematics.
Now I have my character here, and I am just going to put him into Wireframe mode so we can kind of see what we're doing with him. And I want to take the legs and put an inverse-kinematics chain at the ankle so that way I can keep the feet planted on the ground. So we are going to do this by going into Pose mode. Now we are going to do this by creating an object to use as our end effector for the inverse kinematics. So I'm going to add in just an empty object.
And this is just an object that doesn't render, and we can use this as our end point of our IK chain. Now I am going to go ahead and rename this. We are going to call this IK_Right, so it's the right side IK, so I am going to move it under that ankle there. And this is a little big, so I am just going to go ahead and scale it down so it's a little bit more proportional to my character. And I just want to make sure that it is underneath that ankle or is close to that ankle bone as I can make it. So now once I have that placed, I can right- click to select my armature and go into Pose mode.
Now what I want is I want this bone here to point to this object. And that way, when I move the object, it will control the chain. So we can create IK by using a constraint. Bones in Pose mode have an additional tab in their Properties panel, and that's called Bone Constraints. You will not see this in Edit mode. So if I go into Edit mode, that disappears, so we have to be in Pose mode. Select the bone with a little chain on it and we hit Add Constraint > inverse kinematics.
And now it's going to ask you for two things. One is what is the Target? And that's going to be IK_Right, and notice how when I do this it snaps to that object. The other one is called the Pole Target, and that basically just controls where the knee is pointed. Because this character has such tiny, little knees, we probably won't need to worry about that. Now once I have this in place, you can see how a little line shows up. And this basically controls the entire chain. So I have my IK actually goes not just from my ankle to my hip, but actually to the center of the character.
So if I right-click on IK_Right, you can see how when I move that, it's actually moving this character at the hip, which really is not what I want to do. So I am going to go ahead and select this bone, and make sure I'm still in Pose mode, and then under the Bone panel, you will see we have a rollout here for Inverse Kinematics. And what we can do is we can actually just turn off inverse kinematics for this bone, so I am just going to go ahead and lock this down in all three directions, and notice how that kind of just goes right back into place.
And then when I move this bone, it will just move these two bones rather than the entire chain. So this now allows me to position and move the character. So if I were to go back into Object mode here, I can move my entire character and his feet will still stick to those objects.
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