Game Development Reference
In-Depth Information
Figure 7.7
A chain of bones
with IK. Only the
orange IK bone is
being moved; the
rest follow.
For example, when posing an arm grabbing an object, the animator would have to
pose the individual parts of the arms as they reach out for the object; this is often referred
to as forward kinematics (FK). With IK, however, the animator needs to simply grab the
hand bone, or whichever bone is set as the IK bone, and bring it to the object. The rest of
the arm will follow.
Now that you understand how bones relate to and interact with one another, it's time
for you to learn about how to build an appropriate armature for game characters.
Anatomy of an Armature
Unity can give an idea of how an acceptable game rig is built. Like other engines, Unity
employs
ragdoll physics
when creating “dead” versions of character models. Ragdolls
are rigs with loose joints that crumple in accordance with the engine's physics system
(Figure 7.8).
To create ragdolls, Unity asks for specific bone callouts/names. The list is a use-
ful guide for creating your own rigs, as you can create bones that will correspond with
Unity's own armature-related systems (Figure 7.9).
While creating your armature according to Unity's list may seem very software spe-
cific, the outcome will be a good basic armature that can be used in multiple engines.
Furthermore, creating your armature according to Unity's list will allow your model to
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