50 great recipes for giving soul to your characters by building high-quality rigs
This article is about our character’s torso: we’re going to see how to create hips, a spine, and a neck.
Aside from what you’ll learn from here, it’s important for you to take a look at how some of those rigs were built. You’ll see some similarities, but also some new ideas to apply to your own characters. It’s pretty rare to see two rigs built the exact same way.
A human spine, also called vertebral column, is a bony structure that consists of several vertebrae (24 or 33, if you consider the pelvic region). It acts as our main axis and allows us a lot of flexibility to bend forward, sideways, and backward. And why is this important to know?
That number of vertebrae is something useful for us riggers. Not that we’re going to create all those tiny bones to make our character’s spine look real, but that information can be used within Blender. You can subdivide one physical bone for up to 32 logical segments (that can be seen in the B-Bone visualization mode), and this bone will make a curved deformation based on its parent and child bones. That allows us to get pretty good deformations on our character’s spine while keeping the number of bones to a minimum.
This is good to get a realistic deformation, but in animation we often need the liberty to squash and stretch our character: and this is needed not only in cartoony animations, but to emphasize realistic poses too. We’re going to see how to use some constraints to achieve that. We’re going to talk about just the spine, without the pelvic region. The latter needs a different setup which is out of the scope of this article.
Below the Segments field there are the Ease In and Ease Out sliders. These control the amount of curved deformation on the bone at its base and its tip, respectively, and can range from 0 (no curve) to 2.
Since these bones are already set to deform the mesh, we could just add some shapes to them and move our character’s torso to get a nice spine movement. But that’s not enough for us, since we also want the ability to make this character stretch.
The Copy Location constraint here is added because there is no pelvic bone in this example, since it’s creation involves a different approach which we’ll see in the next recipe, Rigging the pelvis. With the pelvic bone below the first spinal bone, its location will drive the location of the rest of the chain, since it will be the chain’s root bone. Thus, this constraint won’t be needed with the addition of the pelvis. Make sure that you check out our next recipe, dedicated to creating the pelvic bone.
This constraint should be enough for stretching, and we may think it could replace the Copy Rotation constraint. That’s not true, since the StretchTo constraint does not apply rotations on the bone’s longitudinal Y axis. So, let’s add a Copy Rotation constraint.
When you finish setting these constraints and applying the rig to the mesh through weight painting, you can achieve something stretchy, as you can see in the next screenshot:
The file 002-SpineStretch-complete.blend has this complete recipe, for your reference in case of doubts.
When creating spine rigs in Blender, there’s no need to create lots of bones, since Blender allows us to logically subdivide each one to get soft and curved deformations. The amount of curved deformation can also be controlled through the Ease In and Ease Out sliders, and it also works well with stretching.
When you scale a bone on its local Y axis in Pose Mode, it doesn’t retain its volume, thus the mesh deformed by it would be scaled without the stretching feeling. You must create controller bones to act as targets to the Stretch To constraint, so when they’re scaled, the constrained bones will stretch and deform the mesh with its volume preserved.
You should notice that the spine controllers will be hidden inside the character’s body when you turn off the armature’s X-Ray property. Therefore, you need to create some custom shapes for these controller bones in order to make your rig more usable.
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