9

Toy Car 767
such that the Analyze World utility generates
no warnings.
To a ss ign r igi d bodies to a Toy Car :
1.
Create the Toy C a r helper and the objects to
connect using it, as described above.
2. On the Propert ies rollout, click the Chassis pick
button, and then, in one of the v iewports, select
the object to use as the chassis.
TheToyCariconmovestothechosenrigid
body. By default, the icon is aligned w ith
the chassis’s local space. reactor can use this
orientation as a guide for the directions of the
suspension and wheel axes.
3. Add your car’s wheels to the helper. You can
add wheels to the toy car either by pick ing or
using a selec tion list:
• Click the Pick button and then select the
object to use as a wheel.
• Click the Add button and then use the
dialog to select one or more objects to use
as wheels.
By default, reactor uses the icon orientation
(taken from the chassis) to provide the
directions of the wheels’ spin and suspension
axes. Each spin ax is is aligned with the icon’s
X axis and passes through the relevant wheel’s
pivot point. The suspension axes are aligned
w ith the icon’s Z axis, and also pass through
each w heel’s pivot point.
Note: For this to work, make sure that the wheels
are oriented correctly relative to the icon before
simulating.
To change the wheel a xis orientation (Icon
Orientation):
1.
Use the Rotate tool to change the toy car icon’s
orientation so that it matches that of the actual
car model.
2. Ensure that Toy Car Properties rollout > Toy
Car Orientation is set to Icon Orientation (the
default).
The wheel axes are aligned with the icon’s new
orientation during the simulation.
To change the wheel axis orientation (Common Local
Orientation):
1.
Ensure t hat the w heel and chassis local spaces
are correctly aligned in world space.
The initial world space orientation of the wheels
relative to the chassis/icon is unimportant
whenusingthisoption,asreactorreorientsthe
bodies so that their local spaces continue to
match during the simulation.
2. On the Toy Car Properties rollout, set Toy Car
Orientation to Common Local Orientation.
3. Use the radio buttons to change the Suspension
and Spin directions relative to the bodies’ local
spaces. By default, the Spin axes are aligned
w ith the wheel and chassis’s local X axes, and
the suspension axes with their Z axes.
To spin t he Toy Car wheels:
1.
OntheToyCarPropertiesrollout,turnonthe
Spin Wheels check box.
2. Change the default Ang (Angular) Speed and
Gain values as necessary.
Angular Speed is the target angular velocity
that reactor attempts to achieve for the wheels.
The Gain is the maximum angular impulse that
can b e applied to the wheels in order to achieve
the t arget velocity.