-
Translate this duplicated Ik_Bind_Spine_ hierarchy's root node away
from the spline IK hierarchy so that this whole situation isn't completely
confusing when you try to select and rig up your joints in the 3D
view window.
You now want to create rotate plane IK handles at each joint of the
new Ik_Bind_Spine_ hierarchy by starting with the root and then making
an IK handle that is a single joint long using the IK Handle
tool.
-
Select the first joint and then the very next joint in the hierarchy
going up the spine. Then start the next IK handle's base at the end
location of the previous IK handle that was just created; continue
this process until the end of the spine hierarchy is reached (see
Figure 17.29). This procedure should exactly result in the same number
of IK handles as there are joints in your hierarchy, minus one—the
only joint that does not have an IK handle stuck directly on top of
it should be the root (which will later be point-constrained).
Figure 17.29
Creating rotate plane IK handles at each joint of the new Ik_Bind_Spine_
hierarchy.
Now you will perform a few steps to perfectly line up the rpIk spine
with the spline IK spine.
-
First, point-constrain each one of the rpIk handles to the corresponding
joint that is part of the spline IK hierarchy. Then point-constrain
the root of the Ik_Bind_Spine_ rpIk hierarchy directly to the root
of the spline IK hierarchy (see Figures 17.30 and 17.31).
Figure 17.30
This image shows half of the IK handles as they are being point-constrained
to the corresponding splineIk spine joints.
Figure 17.31
This image shows all of the IK handles after they have been point-constrained
to the corresponding splineIk spine joints. The root of the Ik_Bind_Spine_
has been point-constrained to the root of the splineIk's spine joint
root.
-
Next, connect the scale attributes from each original joint in the
spline IK hierarchy to the scale attributes of the corresponding duplicate
joint in the Ik_Bind_Spine_ rpIk joint hierarchy.
Because these two hierarchies are right on top of each other in the
3D view, the easiest way to select them is by looking at the two hierarchies
side by side in the Hypergraph's Graph, Scene Graph mode. Then hit
the Toggle Free Form Layout button and move the hierarchies side by
side. By doing this, you can see exactly which nodes you need to connect
to each other because each node in the hierarchy is right next to
the corresponding one. Because the hierarchies are exactly the same,
you simply need to open the Connection Editor, select a single spine
joint first, and load it into the left side. Select the corresponding
duplicate Ik_Bind_Spine_ joint second, and load it into the right
side. Then quickly connect the scale attribute of the spine to the
scale attribute of the corresponding IK_Bind_Spine.
-
Next, group all the rpIk handles under one node by selecting them
all and hitting Ctrl+g (see Figure 17.32).
Figure 17.32
Group all the rpIk handles under one node.
You should now have three joint hierarchies that, for the most part,
all move together and are controlled by the low-res control hierarchy.
They have the capability of stretching and compressing, as well as
rotating using an FK approach and translating using an IK approach.
The only part missing is the FK capability to actually twist the low-res
joint hierarchy and have the joints in the high-res joint hierarchy
get the separate portions driven by the twist.
To achieve the desired twisting capability, you will create locators
to serve as weighed poleVector constraints for each rotate plane IK
handle in the rpIk Ik_Bind_Spine_ hierarchy.
