ReadonlyforceMagnitude of the reaction force over the breaking step, in newtons.
ReadonlyjointThe joint that broke. It is already destroyed when this is dispatched.
ReadonlytorqueMagnitude of the reaction torque over the breaking step, in N·m.
ReadonlytypeAlways "jointbreak" (§28).
A joint exceeded its break force or break torque and was destroyed (§28, plan P6-2).
Who produces this (plan P6-2)
PhysicsWorld, not the solver. Break thresholds live at the@fourjs/physicslayer: after each fixed step the world reads every breakable joint's reaction throughSolverJointAccess, compares it against the thresholds, and destroys the joints that exceeded them — so the same threshold means the same thing on every adapter, including adapters whose solver has no breakage of its own. The event is queued with that step's contacts and dispatched afterwards (§6b, §39 step 9), on the JointBreakEvent.joint itself.The arm exists in PhysicsEvent rather than in a separate union so the world's queue stays one type; an adapter whose solver does break joints on its own may report it from
drainEvents, and the world will retire the joint from its registry rather than destroy it a second time.The reported magnitudes
Both are magnitudes over the step that broke the joint, converted from the solver's reaction impulses by dividing by the fixed delta: newtons for JointBreakEvent.force, newton-metres for JointBreakEvent.torque. At least one of them exceeded its threshold; the other is reported as measured, whatever it was.