8

56 Chapter 11: Space Warps and Particle Systems
Inter face
Timing group
On Time/Off Time—Thenumbersoftheframesin
which the space warp begins and ends its effect.
Because Push moves the particles to which it’s
applied over time, no keyframes are created.
Strength Control group
Basic Force—The amount of force exerted by the
space war p.
Newtons/Pounds—This option specifies the units
of force used by the Basic Force spinner.
A pound is about 4.5 Newtons, and one newton is
one kilogram-per-second-squared. When Push is
applied to particle systems, these values have only
subjective meaning because they depend on the
built-in weighting factors and time scaling used
by the particle system. However, when used in a
dynamics system, the value listed is precisely the
value used.
Feedback On—When on, the force varies
depending on the speed of the affected particles
relative to the specified Target Speed. When off,
the force remains constant, regardless of the speed
of the affected particles.
Reversible—When on, if the particle’s speed
exceeds the Target Speed setting, the force is
reversed. Available only if you tur n on Feedback
On.
Tar get Sp eed—Specifies the maximum speed in
units per frame before the Feedback takes effect.
Available only if you turn on Feedback On.
Gain—Specifies how quickly the force adjusts to
approaching the target speed. If set to 100 percent,
the correct ion is immediate . If set lower, a slower
and "looser" response occurs. Available only if you
turn on Feedback On.
Note: Setting Gain above 100 percent can result in
over-correction, but is sometimes necessary to
overcome damping f rom other system settings,
such as IK damping.
Periodic Variation group
These settings introduce variations into the force
by affecting the Basic Force value r andomly. You
cansettwowaveformstoproduceanoiseeffect.