0002712: Teleport + "On Projectile Inpact" is bugged online

Notes
(0014762) Edward-san (developer) 2016-04-28 11:45 edited on: 2016-04-28 11:56	When cl_showonetickpredictionerrors is enabled, this is printed: (255) WARNING! ServerXYZ does not match local origin after 1 tick! X: -2097152, -14680064 Y: -12582912, 2097152 Z: 0, 7340032 client prediction issue? Anyways, does it happen in zandronum 1.0 or even before?

(0014763) fr-blood (reporter) 2016-04-28 15:38	Tested it like 30 times on Zandronum 1.0, and no it didn't happen.

(0014764) Edward-san (developer) 2016-04-28 18:19	The broken changeset is the gametic unlagged addition. When cl_unlagged is off, it doesn't happen.

(0015987) unknownna (updater) 2016-10-14 13:35 edited on: 2016-10-14 13:59	It seems to be caused by the gametic-unlagged working with the tic buffer. If I disable the tic buffer I don't get the desync when cl_ticsperupdate is 1. I believe it's directly related to my observations in 0002859, as it mostly desyncs when joining the game, when respawning, after map resets and after changemap map changes. However, even with the tic buffer disabled it still desyncs a lot if cl_ticsperupdate is 2/3.

(0019392) unknownna (updater) 2018-08-24 01:36	This is still broken in 3.1, even with all the unlagged fixes. It works with a local connection to the server, but if you have some slight latency (30 ping), it'll break and you'll be teleported back to the wrong spot when shooting the switch. Quote from unknownna If I disable the tic buffer I don't get the desync when cl_ticsperupdate is 1. Weird, it seems to desync now even with the tic buffer off in both 3.0 and 3.1, suggesting that it's mostly caused by the unlagged behavior. It's been broken forever it seems, as I'm able to reproduce it in 1.0, and even Skulltag 98d. I must be testing it differently this time or something, because IIRC I isolated the issue to the tic buffer in the past, but now it happens all the time regardless of the tic buffer being on or off. One thing I also observed is that the client spawns multiple TeleportFog actors when teleporting online. It seems to spawn more actors if multiple puffs hit the switch at the same time, for instance when shooting the switch with a shotgun or a SSG.

(0019396) Leonard (developer) 2018-08-24 21:26 edited on: 2018-08-24 21:33	Unlagged was simply never designed to take in account shots that would teleport players. The player's position is changed before unlagged restores its recorded position. Fortunately sector planes aren't affected by this kind of problem as it seems to be impossible to directly change their height (as they always use a thinker as proxy to do so). PR. EDIT: Quote from unknownna One thing I also observed is that the client spawns multiple TeleportFog actors when teleporting online. It seems to spawn more actors if multiple puffs hit the switch at the same time, for instance when shooting the switch with a shotgun or a SSG. Considering edward's note, if you manage to find a replicable misprediction feel free to report it.

(0019414) Torr Samaho (administrator) 2018-08-26 19:37	Thanks for the patch! Added.

(0019505) unknownna (updater) 2018-09-11 14:24	It seems that your fix took care of the main issue in addition to the teleport fog issue with multiple puffs (it still spawns multiple fogs for projectiles, but it also happens offline and is a harmless ZDoom behavior). Nice work! Tested with various ping levels and with cl_ticsperupdate 1, 2 and 3. Quote from Leonard Considering edward's note, if you manage to find a replicable misprediction feel free to report it. I didn't notice any mispredictions other than the multiple teleport fog issue with multiple puffs hitting the switch at the same time, which your fix seems to have taken care of.

This issue is already marked as resolved. If you feel that is not the case, please reopen it and explain why.
Supporters:	FascistCat unknownna Juanba
Opponents:	No one explicitly opposes this issue yet.

Issue History
Date Modified	Username	Field	Change
2016-04-28 09:24	fr-blood	New Issue
2016-04-28 09:24	fr-blood	File Added: teleportbug.wad
2016-04-28 11:45	Edward-san	Note Added: 0014762
2016-04-28 11:45	Edward-san	Status	new => confirmed
2016-04-28 11:55	Edward-san	Note Edited: 0014762	View Revisions
2016-04-28 11:56	Edward-san	Note Edited: 0014762	View Revisions
2016-04-28 15:38	fr-blood	Note Added: 0014763
2016-04-28 18:19	Edward-san	Note Added: 0014764
2016-10-14 13:29	unknownna	Relationship added	related to 0002859
2016-10-14 13:35	unknownna	Note Added: 0015987
2016-10-14 13:41	unknownna	Note Edited: 0015987	View Revisions
2016-10-14 13:45	unknownna	Note Edited: 0015987	View Revisions
2016-10-14 13:58	unknownna	Note Edited: 0015987	View Revisions
2016-10-14 13:59	unknownna	Note Edited: 0015987	View Revisions
2018-08-24 01:36	unknownna	Note Added: 0019392
2018-08-24 21:26	Leonard	Note Added: 0019396
2018-08-24 21:26	Leonard	Assigned To	=> Leonard
2018-08-24 21:26	Leonard	Reproducibility	random => always
2018-08-24 21:26	Leonard	Status	confirmed => needs review
2018-08-24 21:26	Leonard	Target Version	=> 3.1
2018-08-24 21:33	Leonard	Note Edited: 0019396	View Revisions
2018-08-26 19:37	Torr Samaho	Note Added: 0019414
2018-08-26 19:37	Torr Samaho	Status	needs review => needs testing
2018-09-11 14:24	unknownna	Note Added: 0019505
2018-09-11 14:24	unknownna	Status	needs testing => resolved
2018-09-11 14:24	unknownna	Resolution	open => fixed
2018-09-11 14:24	unknownna	Fixed in Version	=> 3.1