9

Car-Wheel Constraint 759
6.
You can also rotate the suspension axis
independent of the spin axis. To do this,
highlight the Suspension Rotation sub-objec t
level; this lets you rotate the suspension axis
w ith respect to the chassis’s spin axis.
To change the suspension limits:
1.
With the car-wheel constraint selected, open
the Properties rollout.
The default limit settings in the Suspension
Parameters group are Min Limit=0.0 and Max
Limit=0.0 . T his means that in a situation
where the constraint spaces are fully alig ned for
the objects, the w heel cannot move along the
suspension axis.
Thelimitsdefinetheallowedmotionofthe
wheel along the suspension axis with respect
to the chassis, and are displayed as a line with
respect to the chassis. This means that from
astablepositionwherethesub-objectsare
aligned, if the lim its are –5 and 10, the wheel
w ill be able to move 10 units away from chassis
along the suspension axis in the direction of
theicon’sarrowand5unitsintheopposite
direction.
2. Change the limits and observe the difference
in the simulation.
3. You can also change Friction for the Car-Wheel
constrain t; this inhibits the wheel’s motion
along the suspension axis.
To spin the wheel:
These controls are found in the Spin Parameters
group.
1. Set the Velocity va lue to the required value.
This is specified in radians per second.
2. Set the Gain. This is the maximum angular
impulse the constraint can apply to maintain
this angular velocity.
Interfa ce
Modifier Stack
Parent S p a ce—At t his sub-object level, you can
move and rotate the representations of spin and
suspension axes for the chassis. This describes
where on the chassis the wheel is attached and also
the direct ions of the spin and suspension axes for
thechassis.Thisisdefinedinchassisspace,which
means that if you alter the position or rotation of
the chassis the axes will move as well and maintain
their offset rotation and translation with respect
to the chassis. When you assign a chassis to the
car-wheel constraint, Chassis Space’s tr anslation
is set to the wheel’s pivot point, the spin axis is
aligned to the wheel’s X axis, and the suspension
axis is aligned to its Z axis. If the car-wheel
constraint is single-bo died, then Chassis Space
represents the world orientation and position of
the constraint.
Child Space—At this sub-object level, you can move
and rotate the representation of the constraint
for the wheel. This describes both the location
on the wheel that the constraint considers as its