9.0

196 RIGID BODIES
DYNAMICS
DYNAMICS
RIGID BODIES 197
If you were to attach two objects using a spring whose Rest Length value is less than
the distance between the two objects, the spring will be stretched because of this
and it will exert a force on the two bodies that will attempt to pull them towards the
rest length. Conversely, if the Rest Length value is greater than the distance between
the two attached objects, the spring will be compressed because of this and will
exert a force on the two objects that attempts to push them away from one another
and towards the rest length.
Limit Force
In some cases, the force exerted by a spring can become too great for the solver
object to process. Hence under Limit Force you can specify the maximum force that
the spring will be allowed to exert.
Lock
If enabled, this option will lock the Below values to be the same as the Above values.
Below
This option and the Stiffness and Damp parameters below it dene the spring’s
behavior when the spring is below its rest length (i.e. compressed). By default, these
settings are ghosted by the Lock option, which locks the Below parameters to the
same settings as the Above parameters. To be able to dene separate values for
compression, disable the Lock option.
Above
This value refers to the spring when it is above its rest length (stretched, that is). If
Above is enabled, the Stiffness and Damp values will be applied while the spring is
stretched. With the option disabled, the spring will be limp when stretched and it
will thus exert no force.
Stiffness
These two input boxes dene the stiffness of the spring for the Below and Above
options. The higher the value, the greater the force that will be exerted by the spring
when it is stretched or compressed. A stiff spring will be much harder to compress
or stretch than a weak spring.