Rigging the Torso and Head

Let’s set up the torso and head. We’ll do something really simple here, but it will help you understand the power of constraints. Refer to Figure 11.2 for the bones referenced in this step.

1. Select the C_D_spine bone, press Shift, and select the C_D_chest bone. Add a Copy Rotation constraint to it. (Don’t worry if the bone gets messed up when you apply the constraint; you still need to set up the constraint parameters.) Set the two fields in Space to be on the Local Space (so the constraint affects the local spaces from the target and the current bone). Now, if you rotate C_D_spine, C_D_chest bone will rotate as well because you will usually rotate the spine as a whole, so this constraint will save you from having to rotate each spine bone individually unless some special pose is needed. In the Copy Rotation constraint parameters, enable the Offset option so it allows you to also rotate the chest manually and the rotation will be added to the rotation that the constraint will perform automatically. Also, in the constraint’s Influence value slider, you can define how much of the target’s rotation the chest bone will copy.

2. Select the bone C_D_head and, on the Bone tab in the Properties Editor, find the Relations panel. Disable Inherit Rotation so the head doesn’t keep the rotation from its parent (the neck). Now, when you rotate the body, the head will remain aligned, which is usually a more natural behavior.

3. Sometimes, you may want the head to follow the neck’s rotation so add a Child Of constraint to the head, in which the target is the neck bone. You may have to click the Set Inverse button to make it work correctly. Now, with the influence of this constraint you can control the amount of effect that the rotation of the neck carries to the head, giving you more freedom in what you want to do. Keep in mind that you can animate the influence so you can change it along an animation. You’ll learn how to animate those kinds of things in the next chapter.