9

Car-Wheel Constraint 761
Par ent—
When on, the constraint has two
bodies and you can designate an object to be
the optional chassis rigid body attached to the
Car-Wheel constraint. When off, the constraint
is single-bodied and the point occupied by the
Parent Space sub-object is the parent.
You assign the chassis by clicking this button and
then selecting a rig id body from any viewport.
Thereafter the button displays the name of the
chassis object.
Child—Displaysthenameofthesecondrigidbody
attached to the constraint. You assign the child
object by clicking this button an d then selecting a
rigid body from any viewport.
Align Spaces To—Use these options to align the
bodies’ local constraint spaces. You can find
out more about each option in Working With
Constraint Spaces (page 2–726).
Lock Rel a ti v e Tr a ns fo r m—When on, the relative
transform b etween the child and parent constraint
spaces is locked: If you move either space i n the
viewport, the other space moves and rotates along
with it, and vice-versa.
Strength group
Strength/Tau—Govern the impulses applied to
the constraint’s bodies in order to maintain the
constraint, and so how strongly the constraint
works to restr ic t their movement. You can find out
more about these parameters in Strength and Tau
(page 2–735).
Suspension Parameters group
Min Limit—The distance the constraint allows the
wheeltomovealongthesuspensionaxisrelativeto
the chassis, in the direction opposite that indicated
by the icon’s suspension arrow. For example, if
Min L imit=–5, then the wheel cannot move more
than five units backwards a long the suspension
axis with respect to the constraint’s spaces.
Max Limit—The distance the constraint allows the
wheeltomovealongthesuspensionaxisrelativeto
the chassis, in the direction indicated by the icon’s
suspension arrow. For example, if Max Limit=10
then with respect to the constraint’s spaces the
wheelcannotmovemorethan10unitsforward
along the suspension axis.
Fr iction —The level of friction applied to the objects
as they try to move relative to each other along the
suspension axis. Available with Havok 1 only.
Strength—Thestrengthvalueofthesuspension
spring. Higher values c ause less vertica l
movement. Available with Havok 3 only.
Dampi ng—The damping value of the suspension
spring.Highervaluessuppressverticaloscillation.
Available with Havok 3 only.
Spin Parameters group
Velocity—This value indicates the angula r velocity
in radians per second that the constraint will seek
toachieveforthewheel.
Gain—This value indicates the maximum angular
impulse the constraint can appl y to attain the
specified angular velocity.
Breakable group
B r ea kab l e—When on, the constraint is breakable.
If its breakable limits are exceeded during
simulation, it ceases to exert impulses on the
attached objects. For more information, see
Breakable Constraints (page 2–735).
Display group
Size—Lets you change the size of the constraint
space display in the viewport.
Reset Default Values—Returns the constraint’s
parameters to their default values.