2009

Fracture pieces are allowed to exist in a state of interpenetration, where
restoring forces are applied to separate them. Many objects sitting in
penetrating states next to each other can result in an unstable system.
To make the system more stable and less prone to exploding:
Try one or more of the following:
1 Reduce the
Scale Tolerance value on page 4017 in the Fracture Penetrations
group of the reactor utility World rollout. This value can be as low as
–1.0, but –0.1 should suffice in most cases. This scales the Collision
Tolerance
on page 4087 for pieces of a fracture object. A negative Scale
Tolerance value effectively shrinks the object as it is perceived by the
collision-detection system. Pieces that were snug against each other now
have a comfortable safety zone where no collisions take place. This is tied
to the Collision Tolerance value, so changing Collision Tolerance changes
the effective tolerance used when fracture pieces collide with other fracture
pieces. It dramatically reduces unstable oscillations. This is the most
effective thing to try when you wish to avoid explosions.
2 Manually offset the pieces from each other, leaving a physical gap between
all pieces. The gap should be as big as Collision Tolerance * Scale
Tolerance.
3 Increase the Energy Loss value on the Fracture object's Properties rollout.
This is the percent of energy that can be "lost" in the fracture event by
transferring momentum from the broken piece to the unbroken Fracture
object. Increasing it increases the relative velocity between the newly
fractured piece and the remaining unfractured pieces. Ultimately this
reduces the chances of a chain-reaction of unstable oscillations.
4 Increase the Separation Time value and/or decrease the Velocity Cap in
the
Fracture Penetrations on page 4017 group of the World rollout. This
controls how aggressively reactor pushes the pieces out of a state of
interpenetration. After doing this you may notice visible interpenetrations.
5 Slice up your object in a different configuration. Avoid creating very small
pieces, especially if they are right next to very large pieces.
6 Turn on the Use Connectivity check box on the Properties rollout of the
Fracture helper. When connectivity is enabled, clumps of pieces that are
disconnected from other clumps but still internally glued to each other
are set free to move independent of the other clumps. This serves to create
gaps between fractured pieces earlier, so unstable oscillations won’t
happen.
4018 | Chapter 16 reactor