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Ghost items are still a thing

 
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Oxyde
Dominating!


Joined: 01 Feb 2012
Location: France (67) Host: Zero Dawn

PostPosted: Mon Mar 19, 2018 11:42 pm    Post subject: Ghost items are still a thing Reply with quote

Salut,

I think I found out why ghost items still exist, and it's much more simple one would think. This was asked by phenex2 years ago (here for reference) when the bug was thought to be resolved. The issue is in fact linked to this bug, it's actually an extended side-effect.

If you the provided sample wad: test_ammo_depleted.wad, you can easily reproduce in C/S mode the bug described previously, but this is where things get tricky;
    Let's say you have 200 bullets.
    You fire with your pistol once.
    Your ammo should be 199.
    Your client will however display 200.
    Since you have 199 according to the server, you should be able to pick-up any bullet ammo refill.
    If you try to pick one up however, your client will not tell you that you picked this item up.
    In the result, your pick-up item will be on the ground according to your client, but not on the server, leaving you to ammo desync issues.


I'd say this is a rather easy fix though I'm no developper.
I hope this helps track down issues!
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Kilgore
Air Cavalry


Joined: 17 Jun 2003
Location: Up the river

PostPosted: Wed Mar 21, 2018 10:25 am    Post subject: Reply with quote

The ghost items are related to the ammo count problem indirectly because they're both due to a common netcode problem: out of order packet delivery.

There is no way to fix out-of-order in a *general* way short of moving to TCP instead of UDP (which would make the game unaplayable on the net). Therefore, the only way to handle these problems is on a case by case basis. So please don't mix the bugs and tell us: do you still see ghost items?

And no.. out of order problems are not easy to fix at all because they happen randomly.
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Oxyde
Dominating!


Joined: 01 Feb 2012
Location: France (67) Host: Zero Dawn

PostPosted: Wed Mar 21, 2018 2:01 pm    Post subject: Reply with quote

Kilgore wrote:
So please don't mix the bugs and tell us: do you still see ghost items?

In the case mentionned above; 100% of the time
On other cases; Depends on what the server's performance is. Home hosted servers are subject to have these issues, whereas dedicated generally do not (I have yet to notice it when this happens).

Kilgore wrote:
The ghost items are related to the ammo count problem indirectly because they're both due to a common netcode problem: out of order packet delivery.

I understand that we want to have the server rule out some gameplay metrics, but for the sake of smoothness, would it possible to make these metrics client based? What would prevent this? I get that this likel involve a huge backroll on the work done, but aside from that, what would be the reason?
I'm not challenging your reply in any way, I'm just trying to understand how all of this works.

Kilgore wrote:
There is no way to fix out-of-order in a *general* way short of moving to TCP instead of UDP (which would make the game unaplayable on the net). Therefore, the only way to handle these problems is on a case by case basis.

So I guess this is one of those cases then!
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Krawa
There is a limit


Joined: 23 Nov 2008
Location: #SDA

PostPosted: Sun Apr 29, 2018 3:19 pm    Post subject: Reply with quote

How to reproduce ghost items:
- run a server with ammo_test1a (in LAN it happens only in rare cases, with ping it happens sometimes)
- keep shooting chaingun or plasma, collect its ammo type and run the whole row.
- So you pick up all ammo while shooting and always hit the ammo limit.

Moved to confirmed.
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