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Sliding and Rotational Joints (HI Solver) 441
directionachainwillbend,whichangleachain
will tend to rotate toward.
Note: Sliding joints are implemented in the HI
Solver, but they do not take part in an IK solution.
They do, however, take part during FK interact ive
manipulation.
Use the HD S olver if you need to animate sliding
joints with inverse kinematics.
Pr ocedur es
Example: To set the direction an IK chain will bend
(preferred angle):
To underst and setting t he preferred angle it helps
to use a simple example.
1. Go to Create panel > Systems and turn on
Bones.
2. Turn on Assign to Children and make sure the
HI Solver is displayed in the Solver name field.
3. IntheTopviewport,createabonechainoffour
bones in a straight line .
4. Turn on the Auto Key button, and move the
time slider to fr ame 50.
5. Select and m ove the goal so it is close to the
root node.
6. Select any bone in t he chain.
7. On the Hierarchy panel > IK panel, open the
Rotational Joint rollout.
8. There are three axes. Find the one with the
preferred angle that is not zero.
9. Change the preferred angle. If it is negative
make it a positive one.
10. Play the animation, see how changing the
preferred angle can redefine the direction of
the rotation.
To set rotational joint limits on a hierarchy of objects
or a bon e chain :
1.
Create a bone chain or a hierarchy of objects.
2. Select any object in the chain.
3. On the Hierarchy panel > IK panel, open the
Rotational Joint rollout.
4. If you want to limit an axis, turn on Active and
Limited, and set the v alues of From and To. The
hierarchy will rotate in the viewport.
Tip: Pressing the From and To labels instantly
rotates the bone to those angles.
Interfa ce
Sliding Joints rollout
X, Y, Z Axis g roups
Active—Activatesanaxis(X/Y/Z).Allowsthe
selected object to slide on the activated axis.
Limited—Limits the range of motion allowed on an
active axis. Use in conjunction with the From and
To spin ners. Most joints are limited in their range
of motion along an active axis. For example, a
piston slides only within the length of its cylinder.
From a nd To spinner s—Determine for position
limits. Use in conjunction with the Limited
func tion. Clicking the labels From and To moves