9.0

172 SOLVER OBJECT
DYNAMICS
DYNAMICS
SOLVER OBJECT 173
Using a smaller object as a
proxy, you can use a higher,
more reliable Eps value. The real
sphere in the diagram is in the
process of rebounding, but it is
actually the smaller proxy that
has triggered the rebound by
entering the Eps region. Without
a proxy eps object, a much lower
- and therefore less reliable - Eps
value would be needed.
Collision Use Rest Speed, Collision Rest Speed
When you slide an object over a surface using Dynamics, under some circumstances,
the object may start to ‘sink’ through the surface.
The Collision Rest Speed parameter is designed to prevent this sinking from happening.
When the Use option is enabled, it will give the sliding object a little push away from
the surface (in the direction of the surface’s normal, that is).
To prevent this little push from being added to rebounding objects that are not sliding,
the push will be exerted only if the object’s velocity in the direction of the surface is
below a certain velocity — this threshold velocity is the Collision Rest Speed.
A . Collision Use Rest Speed
enabled. B. Collision Use Rest
Speed disabled. The Rest Speed
parameter helps to prevent
sliding objects from penetrating
the surface they are sliding over.
Particularly with complicated spring-mass systems or soft bodies, an inappropriate
integration method can create unexpected behavior. This unusual behavior is possible
in all existing dynamics engines.
Also possible are instable states with which no realistic motion can be achieved
regardless of the integration settings. Such states can be tackled only by using a new
spring arrangement or by adjusting the masses, spring forces and damping.
For an object to rest on a
surface, the distance between
the object and surface must be
less than the Eps distance and
the object’s velocity must be less
than the Collision Rest Speed.
Static drag will then take hold.