coral sundial
I have the weirdest desync bug: Two P2P Clients run exactly the same code, and both use checksums over the gamestate for each frame to detect desyncs.
The game is currently spawning a single enemy which walks towards a point, and when it is in range of 200px to the point, a Shoot event is created that creates a bullet flying towards the enemy.
The Problem is that one client creates the event two frames before the other client.
I'll post the logs from the two clients below.
Client 1:
DEBUG schedule_systems.rs:239 advancing to frame: 1065
DEBUG main.rs:291 Hash 5467956109735517851 for Transform Vec3(-23.927162, -13.672664, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1066
DEBUG main.rs:291 Hash 7166591019787228965 for Transform Vec3(-28.268377, -16.153358, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1067
DEBUG main.rs:291 Hash 12126291388371328420 for Transform Vec3(-32.609592, -18.634052, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1068
DEBUG main.rs:291 Hash 5695548808051519194 for Transform Vec3(-36.95081, -21.114746, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1069
DEBUG systems/s_combat.rs:7 Reading event Shoot with event<Shoot>#0: Shoot { shooter: Entity { index: 1280, generation: 1 }, shooter_pos: Vec2(-210.0, 0.0), target: Entity { index: 1287, generation: 1 } }
DEBUG main.rs:291 Hash 14959565375808988966 for Transform Vec3(-41.292027, -23.59544, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 7738408126710164083 for Transform Vec3(-205.0482, -0.6925577, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1070
DEBUG main.rs:291 Hash 3236172639144371214 for Transform Vec3(-45.633244, -26.076134, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 2545381034499888094 for Transform Vec3(-200.11041, -1.4788008, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1071
panicked at main.rs:258:25:
Desync on frame 1070. Local checksum: A49D2A3C6B952309, remote checksum: EB4861B41975EC39
Client 2:
DEBUG schedule_systems.rs:239 advancing to frame: 1065
DEBUG main.rs:291 Hash 5467956109735517851 for Transform Vec3(-23.927162, -13.672664, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1066
DEBUG main.rs:291 Hash 7166591019787228965 for Transform Vec3(-28.268377, -16.153358, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1067
DEBUG systems/s_combat.rs:7 Reading event Shoot with event<Shoot>#0: Shoot { shooter: Entity { index: 1280, generation: 1 }, shooter_pos: Vec2(-210.0, 0.0), target: Entity { index: 1287, generation: 1 } }
DEBUG main.rs:291 Hash 12126291388371328420 for Transform Vec3(-32.609592, -18.634052, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 9444561451960285634 for Transform Vec3(-205.02736, -0.5223531, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1068
DEBUG main.rs:291 Hash 5695548808051519194 for Transform Vec3(-36.95081, -21.114746, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 5688656653283960953 for Transform Vec3(-200.06447, -1.1303962, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1069
DEBUG main.rs:291 Hash 14959565375808988966 for Transform Vec3(-41.292027, -23.59544, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 10314514317292871243 for Transform Vec3(-195.11378, -1.8308796, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1070
DEBUG main.rs:291 Hash 3236172639144371214 for Transform Vec3(-45.633244, -26.076134, 27.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG main.rs:291 Hash 16460831592429421617 for Transform Vec3(-190.17828, -2.6314015, 28.0), Quat(0.0, 0.0, 0.0, 1.0)
DEBUG schedule_systems.rs:239 advancing to frame: 1071
panicked at main.rs:258:25:
Desync on frame 1070. Local checksum: EB4861B41975EC39, remote checksum: A49D2A3C6B952309
On Client 1, the enemy walks towards the point in frame 1065 (see the Transform component), and in frame 1069 the Shoot event is created when the enemy is at Vec3(-41.292027, -23.59544, 27.0).
On Client 2, the enemy has EXACTLY the same coordinates, on exactly the same frames, but the Shoot event is created 2 frames delayed.
This then creates a desync, because the Shoot entity at Vec3(-205.02736, -0.5223531, 28.0) exists two frames earlier on one client.
Note that nothing here is synchronized between the clients because everything here is supposed to be deterministic 😅
Any ideas?
rugged pendant
Is there any communication between the two ?
Also do the functions run in Update ?
A computer randomly speed up and down based on too many factors to list, so doing anything deterministic without using the internal clock (the closest thing to perfect) would yield varying results.