The death cycle is deterministic
A scripted lap - full throttle, a steer, a crash at speed, the burn, the tumble, death, respawn, a second crash, a second respawn - now plays out bit-identical between identical runs and across 30 and 144 fps under RP412PHYSICSHZ. Ninety of ninety samples exact in the repro pair, sixty of sixty across frame rates, max difference 0.000000. The crash was already deterministic; this makes the RECOVERY deterministic, and it took five pieces, every one found by measurement: - The respawn teleport moves onto the vehicle's own step grid. VTV::ScheduleRespawn stores it and BeginStep applies it at the first step whose clock reaches the due time, teleport and turn-toward-goal together, because the goal flip reads the POST-reset heading. The old path applied the Reset from the event queue, which runs on wall clock, and identical runs diverged on the first step after the pod stood back up. - The handler keeps its Reset for the FIRST spawn of a mission, gated by a flag rather than by mode. A Mover is born in StasisState and the first Reset is what wakes it; gating on "is fixed stepping on" - the first attempt - skipped that wake-up and parked the pod frozen at its spawn point for an entire race. The scripted-lap harness caught it in one run. - The vehicle stamps its own death clock, at the single site that sets BurningState - inside the step machinery, which is why the crash measured exact. The schedule anchors to the death, the last step-exact event in the chain. - The due time is quantized to a half-second grid ANCHORED AT THE DEATH. The instrument showed the naive anchor was four seconds stale by scheduling time: the fry chain reposts itself at wall-clock Now()+2.0 and the drop-zone reply lands about five sim-seconds after death, jittered by a few steps of queue timing. Firing "next step" inherited that jitter whole. Rounding up to the next half-second after the death puts hundredths of jitter against tenths of headroom, so every run lands in the same cell - and the felt delay stays the six-ish seconds it has always been. - The out-of-world tumble draws from a per-vehicle random stream seeded by creation order. The global Random is shared with the frame loop's consumers - particles, mostly - so its position at the moment a burning pod drew from it depended on how many frames had rendered, and the kick went straight into angular velocity. Last wall-clocked input in the whole death cycle. The respawn scheduling and firing log under RP412PHYSTRACE in run-comparable terms - pad identity, due offset, lateness - because those lines are what cracked this: "due in -4.06 sim-s" said more in one glance than three rounds of hypothesis. Still outside the claim: multi-vehicle contact (DynamicBounce writes the victim's state from the striker's step) and network play. That is the lockstep frontier, and it now has a harness waiting for it. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Claude Fable 5
+128
-3
@@ -803,9 +803,17 @@ void
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Check(*damageZones);
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(*damageZones)->TakeDamage(collision_damage);
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localVelocity.angularMotion.x += 8.0f * Random - 4.0f;
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localVelocity.angularMotion.y += 8.0f * Random - 4.0f;
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localVelocity.angularMotion.z += 8.0f * Random - 4.0f;
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//
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// The tumble draws from the vehicle's OWN stream, not the
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// global Random - the global one is shared with the frame
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// loop's consumers (particles, mostly), so its position here
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// depended on how many frames had rendered. This kick goes
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// straight into physics state; it was the last wall-clocked
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// input left in the whole death cycle.
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//
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localVelocity.angularMotion.x += 8.0f * TumbleRandom() - 4.0f;
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localVelocity.angularMotion.y += 8.0f * TumbleRandom() - 4.0f;
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localVelocity.angularMotion.z += 8.0f * TumbleRandom() - 4.0f;
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}
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}
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worldLinearAcceleration = zippy_accel;
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@@ -1273,6 +1281,18 @@ VTV::VTV(
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boosterSmokeDensity = 0.0f;
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doorHitNormal = Vector3D::Identity;
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lastDoorHit = Time::Null;
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respawnPending = False;
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respawnHaveGoal = False;
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deathClockValid = False;
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//
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// Creation order is deterministic, so each vehicle's tumble stream
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// is too - see TumbleRandom in the header.
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//
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{
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static unsigned long tumble_births = 0;
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tumbleSeed = 0x52503431UL + 7919UL * ++tumble_births;
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}
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heightAboveTerrain = 0.0f;
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forwardVelocity = 0.0f;
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hornBlast = -1;
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@@ -1685,6 +1705,101 @@ void
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Check_Fpu();
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}
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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void
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VTV::ScheduleRespawn(
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const Origin &new_origin,
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const Time &due,
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const Point3D &face_toward,
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Logical have_goal
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)
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{
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Check(this);
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Check(&new_origin);
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respawnOrigin = new_origin;
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respawnDue = due;
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respawnGoal = face_toward;
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respawnHaveGoal = have_goal;
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respawnPending = True;
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Check_Fpu();
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}
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// The pending respawn lands here, at the top of the first STEP whose clock
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// has reached its due time - the same step count after death on every run
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// and every frame rate. The old path applied the Reset from the event
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// queue, which runs on wall clock: the crash was deterministic and the
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// recovery was not, measured as two identical runs diverging on the first
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// step after the pod stood back up.
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//
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// The turn-to-face-the-scorezone flip is the same arithmetic
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// RPPlayer::PointVTVTowardGoal does, done here because it reads the
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// POST-reset heading - it belongs to the same step as the teleport.
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//
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void
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VTV::BeginStep()
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{
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Check(this);
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if (respawnPending && !(GetLastPerformance() < respawnDue))
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{
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respawnPending = False;
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{
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static int diag = -1;
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if (diag < 0)
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{
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const char *setting = getenv("RP412PHYSTRACE");
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diag = (setting != NULL && atoi(setting) != 0) ? 1 : 0;
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}
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if (diag)
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{
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char buffer[120];
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sprintf(buffer,
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"PhysTrace: respawn fired, %.4f sim-s late, pad %.2f,%.2f\n",
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(double)(Scalar)(GetLastPerformance() - respawnDue),
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(double) respawnOrigin.linearPosition.x,
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(double) respawnOrigin.linearPosition.z);
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DEBUG_STREAM << buffer << std::flush;
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}
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}
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Reset(respawnOrigin, RegularReset);
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if (respawnHaveGoal)
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{
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Vector3D to_goal;
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to_goal.Subtract(respawnGoal, localOrigin.linearPosition);
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UnitVector current_heading;
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localToWorld.GetFromAxis(Z_Axis, ¤t_heading);
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Scalar length_to_goal = to_goal.LengthSquared();
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if (length_to_goal > SMALL)
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{
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Scalar dot_prod =
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(to_goal * current_heading) / Sqrt(length_to_goal);
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if (dot_prod >= 0.0f)
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{
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Quaternion turn_around;
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Quaternion y_roll(0.0f, 1.0f, 0.0f, 0.0);
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turn_around.Multiply(
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localOrigin.angularPosition, y_roll);
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localOrigin.angularPosition = turn_around;
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localToWorld = localOrigin;
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}
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}
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ForceUpdate();
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}
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}
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Mover::BeginStep();
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Check_Fpu();
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}
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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void
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@@ -3100,6 +3215,16 @@ void
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if (damageLevel >= 1.0f)
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{
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vtv->SetSimulationState(VTV::BurningState);
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//
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// Stamp the death on the vehicle's own step clock, here at the
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// one site that declares it dead. The respawn schedule anchors
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// to this instant - the last step-exact event in the death
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// chain - so the recovery lands the same number of steps after
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// the crash on every run. Marked once; repeated damage while
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// already burning does not move it.
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//
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vtv->MarkDeathClock();
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}
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//
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