Graphics Reference
In-Depth Information
What we're going to do is create a second set of arm bones that operate with an IK controller. Then, we
will add constraints that cause the original arm bones to follow these IK arms' transformations exactly.
Finally, we'll turn off the influence of these transformation constraints so that the arms are free to move
with forward kinematics again. A controller will be created that toggles the influence of the constraints,
letting you switch between FK and IK as needed during the animation process.
The first step is to duplicate the arm bones. You already know how to do that: Select them in Edit mode
and press Shift-D, then Enter. Pressing the Enter key after the duplication ensures that the bones are in
the exact spot as the originals. If you try to use the LMB to accept the duplicates, it can be easy to acci-
dentally move them. Note that you should only duplicate the upper and lower arm bones. Don't include
anything from the hand or shoulder.
With these two new bones still selected, use the M key to send them to another layer. Bones within an
armature have their own layering system, just like objects do with scenes. Rigs can become complicated,
and you don't always want to see every bone. In fact, you'll usually want to organize your rigs so that
only control bones are visible. So far, every bone we've worked with has appeared on bone layer 1. It
doesn't really matter to which layer you send these two bones, as long as you decide on a consistent
scheme. I would suggest:
●
Layer 1: Main control bones
●
Layer 2: Facial controls (see Chapter 10)
●
Layer 3: Hand and other “detail” controls
●
Layer 4: Deform bones
●
Layer 5: Other helper bones
Anyway, those bones are gone for now. In the scheme we've just laid out, let's say they're sent to bone
layer 5. Select the tail of the original lower arm bone (the wrist joint), and snap the 3D cursor to it with
the
Snap Cursor to Selected
operation (Shift-S). Use Shift-A to add a new bone. Name it something
like “arm_control_ik.” This will be the bone that we use when we want to animate the arm using Inverse
Kinematics. With this new bone selected, use the M key again, and this time hold down Shift key and
click bone layer 5. Both bone layers 1 and 5 should be selected (that's what holding down the Shift key
did), meaning that this controller bone will appear on both layers.
Figure 9.25
shows both the Armature and Bone contexts
at this point. Notice that the panels displaying the bone
layer buttons are similar. It is sometimes easy to get con-
fused as to which panel you are working with. Remember
that the layer controls in the Bone context affect the layers
on which the selected bone resides, while the ones in the
Armature context control which bone layers are currently
shown in the 3D view. Up until now, we've only been
displaying bones on layer 1. LMB click bone layer 5 (or
wherever you sent those other bones) in the armature prop-
erty layer controls.
Figure 9.25
The different sets of layer controls for
armatures.
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