9
Cloth Modifier 579
specify what is made of cloth, and what is a solid,
collision object.
Because Cloth is a modifier, an instance of it is
assigned to each object to be incl uded in the Cloth
simulation. This includes all cloth and collision
objects. Be aware that two cloth objects with two
separate applications of the Cloth modifier will
not interact with one another. There are a couple
of ways to include objects in the simulation:
• Select all of the objects at once and apply the
Cloth m odifier to them.
• Apply Cloth to one or more objects and then
add objects with the Add Objects button,
available on both the Object rollout and the
Object Properties dialog (page 1–602).
Units of M easure
Impor tant: The following information is necessary only
if you change the system unit after applying the Cloth
modifier. If you change the system unit before applying
Cloth, the modifier automatically adjusts the cm/unit
setting.
Itisimportanttothinkaboutsizeindoingclothing
simulations. A very large flag behaves differently
from a handkerchief. If the scale is off, then
the simulation wil l be off. Because Cloth deals
with real-world physics, it works in real-world
units. Th is means that Cloth needs to know the
relationshipbetweenunitsin3dsMaxandunitsin
its own world.
Forexample,supposeyoucreateaplanethatis
10x103dsMaxunits. Ifyouwantthisplaneto
behave like a 10-inch x 10-inch handkerchief, you
would tell Cloth that 1 3ds Max unit=1 inch. If you
want it to behave like a 10-foot x 10-foot bed sheet,
you would tell Cloth that 1 3ds Max unit=1 foot.
Except as noted at the start of this section, Cloth
ignoresthe3dsMaxSystemUnitsSetup(under
Customizemenu>UnitsSetup>SystemUnits
Setup). Cloth has its own units setup, which
is determined by the cm/unit parameter on the
Simulation Parameters rollout. This tells Cloth
how man y centimeters (cm) correspond to each
3ds Max unit. One inch equals 2.54 cm, s o the
default sett i ng of 2.54 means that one 3ds Max unit
corresponds to 1 inch.
Followingistheproceduretofollowtodetermine
what setting to use here.
1. Usethemeasureutilityortapehelperto
measure some dimension of your cloth (or
character) in 3ds Max units (call this number
x).
2. Decidehowbigyouwantthisobjecttobeinthe
real world Convert this number to centimeters.
Ifyouhavethedimensionininches,simply
multiply by 2.54 (call this number y).
3. cm/unit=y/x
Here is a quick example: You import a file,
man.obj, into 3ds Max, and want to put a shirt on
him.
1. Using the Measure utility, you find that the man
is 170 3ds Max units ta ll. So y=170.
2. You determine that this man is about 6 feet tall.
6 feet=72 inches.
And 72 inches=72x2.54=182.88cm. So
x=182.88
3. So now you have the values to make
sure the shirt behaves correctly.
Cm/unit=y/x=170/182.88=0.929. Or
you can round the spinner’s value up to 1.0,
since pinpoint accuracy is not needed here.
Fabric Behavior
Cloth provides many different ways to set up fabric
beha viors. You can make your cloth behave like
leather, si lk, burlap, and any thing in between.