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588 Chapter 8: Modifiers
cm/u nit—Determines how many centimeters there
are per 3ds Max system unit.
Cloth automatically sets cm/unit to the equivalent
of 2.54 centimeters p er inch (the default system
unit in 3ds Max). For example, if you set the
system unit to one foot, Cloth automatically sets
cm/unit to 30.48 (12x2.54).
Size and scale are important when doing cloth
simulation because a 10-foot curtain behaves much
differently from a one-foot square handkerchief,
even if they are made from the same fabric.
Ear th—Click this button to set the Gravit y value
to tha t of planet Earth.
Gravity —When on, the Gravity value (see
following) affects cloth objects in the simulation.
[Gr av it y va lue]—The force of gravity in cm/sec
2
.
A negat ive value applies g ravitational force
down ward. A positive value (i.e., no sign) means
grav ity w ill act to move cloth objects upward.
ThedefaultvalueissettobethesameasEarth’s
gravity: -980.0 cm/sec
2
.
Step—Themaximumsizeofthetimestepthe
simulator takes.
This value is measured in seconds. The value
must be less than the length of one frame (less
than 0.033333 for 30 fps animation). A value of
0.02 is generally the largest value you want to
use. Reducing this va lue causes the simulator to
take longer to calculate, but will in general give
better results. The simulator will automatically
reduce its time steps as needed, but this is the
maximum value that it will try. This value works
in conjunction w ith the Subsample parameter:
The actual maximum value=Step value divided
by Subsampl value.
Subsa mple—The number of times per f rame that
the software samples the position of solid objects.
Default=1.
At the default value, Cloth samples the solid objects
in the simulat ion once ever y frame. Increasing
this value should help when objects are moving or
rotating quickly, but be aware that the higher you
set the va lue, the slower t he simulation will be.
Start Frame—The f rame at wh ich the simulation
starts. If you change this value after the simulation
has been p erformed, the cache will be moved to
this f rame. Default=0.
End Frame—When on, determines the frame at
which the simulation will stop. Default=100.
Self Collision—When on, detects cloth-to-cloth
collisions. Leaving this off will speed up
the simulator, but will allow cloth objects to
interpenetrate.