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758 Chapter 13: reactor
The Car-Wheel constraint also has spin
parameters. If these are nonzero, the constraint
turnsthewheelduringthesimulation.Youcan
specify a target velocity and a target gain: the
maximum angular impulse that the motor can
applytotherigidbodyinordertoachievethe
target velocity.
A Car-Wheel constraint is simulated if it has
the correct number of rigid bodies attached and
is included in a valid Constraint Solver (p age
2–736).Whennotselected,aninvalidCar-Wheel
constraint is red in the viewport.
Pr ocedur es
To crea te a Car -Wheel constra int :
• Chooseoneoftheaboveoptions,andthen
click in any viewport to add the Car-Wheel
constraint.
Note: The icon’s position has no effect on the
constraint’s behavior.
To att ach objects to the Car -Wheel constrai nt:
1.
Create the constraint and the objects to connect
using it.
2. Ontheconstraint’sPropertiesrollout,click
the Child pick button, and then, in one of the
viewports, select the object you want to use as
the wheel.
This attaches the constraint to the wheel at the
wheel’spivotpoint.Thespinaxisisaligned
to the X axis of the wheel objec t and the
suspension axis is aligned to the Z axis.
3. If you do not want to assign a chassis to the
Car-Wheel constraint, turn off the Parent check
box if necessary.
4. If the Car-Wheel constraint is to be two-bodied,
repeat step 2, using the Parent pick button to
specify the chassis object for the constraint.
To create the constra int a nd a ttach objects in a single
step:
•SeetheScripts (page 2–817) topic.
To change the positions a nd r otations for the bodies:
1.
With the constraint selected, open the Modif y
panel.
2. In the modifier stack open the constraint’s
sub-object list.
3. Access the sub-object lev el corresponding
to the object whose constraint space you
want to move: Parent Space for the chassis or
Child Space for the w heel. If the constraint
is single-bodied, Parent Space represents the
world attachment position and rotation of the
constraint axes.
4. The space, represented by just a spin axis for
the wheel and by the spin and suspension
axes for the chassis, b e comes active in the
viewport and c an be moved or rotated using
theMoveorRotatetool,respectively.Thespace
maintains its position and rotation relative to
its corresponding object. For example, if you
moveorrotatethewheel,ChildSpacemoves
with it.
5. To reset the attachment point to the child’s
pivot, reattach the objects to the car-wheel
constraint or choose the Align Spaces To Child
Body option.