Controls whether the bounce passes also solve contacts that have no bounciness. With this disabled, only contacts with a bounciness above zero take part in the bounce passes. A bounce then does not carry through neighboring bodies in the same pass, so a stack of boxes on a bouncy surface bounces from the bottom box up rather than together. With this enabled, every contact takes part, so a bounce carries through groups of touching bodies within the same simulation step. This visits every contact in the world on every bounce pass, which is significantly more expensive, so only enable it when bodies in contact must bounce together. Carrying a bounce through a taller group of bodies needs more bounce passes.