9

Dynamics Properties Rollout 1479
Ambient and Diffuse Map Lock
In the Maps rollout, the lock button to the right
of the Diffuse Color map button locks ambient
mapping to diffuse mapping. It is on by default.
Usually it makes sense to use the same map for
the ambient and diffuse components. To use
different maps for ambient and diffuse, turn off the
lock button. The map button for Ambient Color
becomes available.
D yna mics Pr operties R ol lout
Material Editor > Standard m aterial > Dynamics Properties
rollout
The Dynamics Properties rollout lets you specify
surfacepropertiesthataffecttheanimationofan
object upon col lision with another object. If there
are no collisions in your simulation, these settings
have no effect. The dynamics propert ies are used
by the Dynamics utility (page 2–686).
Since the Dynamics Properties rollou t is available
at the top level of any material (including
submaterials), you can specify different surface
dynamic properties for each face in an object.
There are also controls in the Dynamics utility that
letyouadjustthesurfacepropertiesattheobject
level, but only the Materials Editor lets you alter the
surface properties at the sub-object level, through
use of a Multi/Sub-Object material (page 2–1594).
As a default, the values in the Dynamics Properties
rollout provide a surface that’s similar to
Teflon-coated hardened steel.
Inter face
B ounce Coefficient—Sets how far an object bounces
after h itting a surface. The higher the value, the
greater the bounce. A va lue of 1 represents a
"perfectly elastic collision," or a bounce in which
no kinetic e nergy is lost. Default=1.0.
If you’ve seen the desktop toy with four ball
bearings swinging back and forth on strings and
hitting one another, you’ve seen an example that
comes ver y close to a bounce coefficient of 1.
Generally, hardened steel or a super ba ll have a
bounce near 1, while lead has a bounce near 0.
Static Friction—Sets how difficult it is for the object
to start moving along a surface. The higher this
value, the more difficult. Default=0.0.
If something weighs ten pounds and sits on Teflon
(a static fr ic tion of near 0), it ta kes almost no force
to make it move sideways. On the other hand, if it
sits on sandpaper, then the st atic friction might
be very high, on the order of 0.5 to 0.8. A static
friction near 1 is very difficult to create in the real
world without adhesives or friction material.
Sliding Friction—Sets how difficult it is for the
object to keep moving over a surface. The higher
this value, the more difficult for the object to keep
moving. Default=0.0.
Once two objects beg i n to slide over one another,
static friction disappears and sliding friction takes
over. Generally, sliding friction is lower than
static friction due to surface tension effects. For
example, once steel starts sliding over brass (a
value of static friction that might run from 0.05 to
0.2), the sliding fr iction d rops to a significantly
lower value, on the order of .01 to 0.1. For s ome
materials, such as specific friction materials like
brake linings, sliding friction is just as high as static
friction because it is used in conjunction with
a nearly frictionless material such as hardened
polished steel.