[Ulduar] Mimiron - VX-001 Rapid Burst hits players who moved out of its facing

Current Behaviour

In phase 2, VX-001 (33651) channels Rapid Burst (63382) straight onto a random player and turns toward them once, when the cast starts. While the 3 second channel runs, the damage bursts (63387 / 64019, 25-man 64531 / 64532, 60 degree cones in front of VX-001) keep following that player as they move. The model keeps pointing where the cast started. Players see the volley change direction partway through and get hit from a direction the model isn't facing, and dodging by watching the model doesn't work.

Video: https://www.youtube.com/watch?v=yEpqq3ZflCE The player stands still in a neutral position, then moves to a new position and holds still there. VX-001 still fires at them after they have already been standing in the new, safe position.

Why: 63382 has SPELL_ATTR1_TRACK_TARGET_IN_CHANNEL. On every periodic tick, AuraEffect::PeriodicTick calls Unit::SetInFront(channel object) for creature casters (SpellAuraEffects.cpp, "Update serverside orientation of tracking channeled auras"). That only changes the server-side orientation; no facing update is sent to clients. The damage cone uses that server orientation, so the cone follows the player while clients keep the facing from the cast start.

A new target is also picked 0.2 s after each channel ends (3.2 s repeat for a 3.0 s channel), so the switch to the next target looks like part of the same volley.

Affected:

• Creatures: VX-001 (33651), Burst Target (34211, never summoned by the current script)
• Spells: Rapid Burst channel (63382), damage 63387 / 64019 / 64531 / 64532, Summon Burst Target (64840), 64841

Expected Behaviour

Each Rapid Burst picks a random player and fires all three volleys (six bursts, alternating left and right cannons) along one line toward the spot the player was standing on when it started. VX-001's model points along that line for the whole volley, so players can see where it is firing and step out of it. Then it picks a new target.

Source

• 3.3.5a client spell data. Rapid Burst comes with its own aim-point spells: 64840 "Rapid Burst" summons creature 34211 "Burst Target" at the enemy's position (effect 28, misc value 34211), and 64841 "Rapid Burst" is a script effect. The burst tooltip (63387) reads "Unleashes a series of short plasma bursts towards a random enemy". The volley is meant to be aimed at a summoned point, not at the moving player.
• TrinityCore implements it that way (TrinityCore 7c13b383, "Scripts/Ulduar: Implement Mimiron"): VX-001 casts 64840 on a random player, the Burst Target casts 64841 on VX-001, and VX-001 channels 63382 on the stationary Burst Target.
• AzerothCore's world DB already has the 34211 template. The current script never uses it.

Steps to reproduce the problem

Needs two players with .gm off (VX-001 never targets GMs), one of them a mage.

1. .tele mimiron, .cheat god, .gm off on both players
2. Engage Mimiron. To skip phase 1, target Leviathan MK II and .damage 5000000
3. In phase 2, have the mage stand right next to VX-001 and the other player about 20 yards away
4. When Rapid Burst targets the mage, blink onto the other player
5. The rest of the volley follows the mage, and every burst hits both players

Any movement during a volley shows the problem, but a blink or teleport makes it obvious right away. In a full raid, where players reposition constantly, it kills players who have already moved out of the line.

Extra Notes

Measured on a local 25-man run (24 client bots running circles around the room at different radii, plus one player). One client logged every facing update the server sent for VX-001 and every Rapid Burst hit, and compared the bearing of each hit player with the last facing clients had been sent. A 60 degree cone reaches at most 30 degrees either side of that facing.

• Targets just running in circles: 22 of 24 volleys hit someone more than 30 degrees off the facing clients were shown (216 of 832 hits; worst 139 degrees).
• Targets that blinked 20 yards along their path when the volley started: 33 of 35 volleys, 720 of 918 hits outside, worst 122 degrees.

One volley from the log. Clients were sent "face 86 degrees" at the start and nothing after. The target blinked, and each burst kept following them:

249.31 FACE angle   86.0
249.35 SPELL 63382  (target at 86)
249.81 burst  target hit at 143  (57 off)
250.32 burst  target hit at 153  (67 off)
250.82 burst  target hit at 163  (77 off)
251.33 burst  target hit at 173  (87 off)
251.81 burst  target hit at -177 (97 off)
252.33 burst  target hit at -167 (107 off)

With the channel aimed at a Burst Target that stays where the player was, the same circling run had no volleys off the shown facing: 26 volleys, 649 hits, none more than 30 degrees off.

Related, but a different symptom: #27225 and #27554 (Spinning Up / Laser Barrage facing).

AC rev. hash/commit

AzerothCore rev. 5c94774263fb 2026-09-15 09:56:03 +0200 (master branch) (Unix, RelWithDebInfo, Static) (worldserver-daemon)

(ChromieCraft's mirror of master. boss_mimiron.cpp is byte-identical to azerothcore-wotlk master as of 2026-09-19.)

Operating system

Arch Linux x64

Custom changes or Modules

The ChromieCraft module set (mod-ale, mod-anticheat, mod-zone-difficulty, mod-progression-system, mod-transmog and others). None of them reference Mimiron, VX-001, 34211 or the Rapid Burst spells.