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colliding, and then updating the scene accordingly. If objects are closer
together than the Collision Tolerance value, reactor considers them to be
colliding. A high Collision Tolerance value results in a stable simulation, but
it can also cause gaps between "colliding" objects.
The default value is 1/10th of World Scale (10 cm if you are modeling using
real-world sizes), and it is a good rule of thumb to always keep it above 1/40th
(4 mm), due to floating point precision limits in the processor. For standard
scenes and object sizes, the default parameters for world scale and tolerance
should be adequate. If you are simulating very small objects where the
tolerance is still to visible, try reducing the World Scale value and the Collision
Tolerance and Gravity accordingly. For more information, see
Scale on page
3896.
Add Deactivator When on, reactor adds a deactivator to the simulation.
The deactivator keeps track of the objects in the simulation and deactivates
(stops simulating) objects that it determines are at rest. This keeps reactor
from wasting system resources simulating objects that aren't doing anything.
When Add Deactivator is on, you have access to two distance parameters for
determining whether an object is moving or not. The reason that there are
two properties rather than just one is for bodies that vibrate. It's possible that
a body can end up vibrating after a collision or some other occurrence. A
vibrating body might vibrate a few millimeters in distance, which would keep
it active for a typical Short Frequency test. However, the object is not really
moving anywhere, so keeping it active wastes CPU time. However, if it vibrates
in place, it fails the Long Frequency test and is deactivated.
■ Short Frequency The minimum distance, usually in millimeters, that an
object must move during each step of a simulation. If an object in a
simulation does not move the specified distance in each step, reactor
deactivates it.
■ Long Frequency Also sets a distance, usually larger than the Short
Frequency value. Long Frequency checks every few steps simulation rather
than at every step. Any object that does not move the required Long
Frequency distance is deactivated.
Add Drag Action When on, ensures that rigid bodies are subject to constant
drag. This damps their linear and angular velocities, so they come to rest
sooner. This is useful, for example, where rigid bodies are joined with
constraints on page 3925, as it helps the constrained bodies to come to rest
despite the forces applied by the constraints.
■ Lin The linear damping applied by Add Drag Action.
■ Ang The angular damping applied by Add Drag Action.
Havok 1 World/Havok 3 World Rollout | 4089