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732 Chapter 13: reactor
Par ent—
When on, the dashpot has two bodies
and you can designate an object to be the parent
body. When off, the dashpot is s ingle-bodied and
the point o ccupied by the Parent Space sub-object
is the parent.
You assign the parent object by clicking this button
and then selecting a r igid body from any view port.
Thereafter the button displays the name of the
parent bo dy.
Child—Displaysthenameofthesecondrigidbody
attached to the dashpot. 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
moreabouteachoptionintheWorking With
Constraint Spaces (page 2–726) sec tion.
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 along with it.
Strength—Governs the size of the impulse the
dashpot applies to each attached body, taking
into account the distance between the attachment
points. The st rength va lue i s mass-dependent.
For example, a Strength value of 10 generates
a different behavior when connecting two 5 kg
bodies than when connecting two 50 kg bodies.
Va lues g reater than or equal to 0 are valid for this
property. Default=1.
Dampi ng—Determines how quickly the oscillation
of the linear dashpot settles down. Damping
governstheimpulseappliedtotheconnected
bodies due to the relative velocities of their dashpot
connection points. Valid damping values are those
greater than or equal to 0 and less than or equal
to 100000. Default=0.1.
Tip: Typically, a damping value of 1/10th of the
stiffness yields good results.
Allow I nterpenetr ati on—When on, collisions are
disabled b etween the dashp ot’s objects, so that
they can pass through each other during the
simulation. Defaults=off.
Disabled—When on, the d ashpot is not added to
the simulation.
Reset Default Values—Click this to set Strength,
Damping,andDisabledtotheirrespectivedefault
values.
Angular Dashpot
Create panel > Helpers > reactor > A Dashpot
Menu bar > reac tor > Create Object > Angular Dashpot
reactor toolbar > Create Angular Dashpot button
Dashpots t ypically serve to cushion impact. An
example of a real-world angular dashpot is a device
connected to a door to keep it from slamming
shut. You can use the Angular Dashpot constraint
to constrain the relative orientation of two rigid
bodies, or the absolute orientation of a rigid body
in world space. When simulating, the dashpot
exerts angular impulses on the bodies to which it
is attached in an attempt to maintain the specified
rotation between the objects. You can specify the
dashpot’s strength and damping, and whether
collisions between the system’s bodies are disabled.
An angu lar dashpot has two sets of axes as
sub-objects. For two-bodied dashpots, these are
specified as offset rotations from the dashpot’s
bodies. For single-bodied dashpots, one
sub-object is an offset rotation and the other is a
world rotation. In a simulat ion, the dashpot tr ies
to maintain a common rotation for these axes.
You do not need to add angular dashpots explicitly
to a simulation, as all valid dashpots in a scene are
added to the simulation by default. A dash pot is
valid if it has the correct number of rigid bodies