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696 Chapter 8: Modifiers
stable the simulation. When using the Midpoint or
Runge-Kutta4 solver, you mi ght not need as many
samples as with Euler. Default=5.
Tip: If your simulation produces unexpected
results, such as object vertices moving to seemingly
random locations, try incre asing the Samples
setting.
Simple Soft Bo dies rollout
Lets the s oftware determine spri ng settings for
theentireobjectautomatically.Alternatively,you
can use the Advanced Springs (page 1–699) rollout
settings to specify spring settings between each
pair of vertices.
Create Simple Soft Body—Generates spring settings
for the object based on the Stretch and Stiffness
settings.
Note: AfteryouuseCreateSimpleSoftBody,
you can change the Stretch and Stiffness settings
without having to click the button again; the
changes t ake effect immediately.
Stretch—Determines how much object edges
can elongate. When Advanced Springs rollout >
Enable Advanced Springs is off, the Stretch setting
is linked to the Advanced Springs rollout > Stretch
Str. and Stretch Sway settings.
Stiffness—Determines how rigid the object
is. When Advanced Springs rollout > Enable
AdvancedSpringsisoff,theStretchsettingis
linked to the Advanced Springs rollout > Shape
Str. and Shape Sway settings.
The differences b etween Stretch and Stiffness
are subtle, and understanding them is further
complicated by the fact the two affect each other.
In addition, how they work depends on object
topolog y. For example, say you create a box, add a
Flex modifier, apply Create Simple Soft Body, and
then set a high Stretch value and a low Stiffness
value. If you use the box in a Flex-based dynamics
simulation, such as dropping it onto a surface
(deflector) with gra vity, you might expect the box
to fall over and flatten out. But instead, because
of the b ox’s topology, w hich causes Create Simple
Soft Body to apply a relatively small number of
shape springs, you’d actually get better results
with a low Stretch value and a high Stiffness value.
However, if you use a sphere of eight segments
instead, you’ll get the collapsing behavior with
the default Stretch and Stiffness settings, and as
expected, increasing r igidity w ith hig her Stiffness
settings.
In soft-body simulations, such as the above-cited
example of dropping an object onto a sur face,
particularly with dense meshes, you might get
betterresultsbyapplyingthemeshtoanFFD
space warp that’s bound to the object. If the
object’s shape isn’t suitable for use with the space
warp, you might have to instead use the Advanced
Springs (page 1–699) rollout settings to apply
springs manually. In such cases, you should create
shape springs between opposite vertices rather
than adjacent ones.
Cloth-like animation usually works best with a
high Stretch setting and a low Stiffness sett ing. For
soft bodies, you would usually use high settings
for both St retch and Stiffness, depending on how
"squishy" you want the object to be.