Player synchronization and examples (and tests kind of) about mdframework HOT 5 CLOSED

I haven't fully read through this yet but I wanted to comment that I have a position synchronization class started for my own game that I'm planning to move to the framework. It supports prediction and interpolation based on the expected RPC rate but there's still a bunch of room for improvement.

References:
https://www.reddit.com/r/godot/comments/8ch20v/help_with_node_sync_over_a_network/
https://gafferongames.com/post/snapshot_interpolation/

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As for Join Synchronization, MDReplicator/MDGameSession should already handle that for you, it will update new players with the networked nodes and any MDReplicated properties.

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Aye they do synchronize on join, however currently as far as I know there is no way for the client to know when synchronization is complete. Nor for the server.

The synchronizer I proposed would allow for the client and server to know when synchronization is completed. Also the game ticks I think could be useful in a lot of situation, particlarly if you are making a network game based on ticks (such as a real time game like transport tycoon or factorio, both of which work on ticks I believe).

That being said, it might be that this is not useful for the framework itself. If that is the case I would just implement this seperately for my own game as I wish to have these features.

Also I would be very interested in your sychronization class once you completed it, I am just about to start on the same thing for my game so if it is added to the framework I would be happy to help test it.

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Ah yeah, the synchronization state is a bit of a special case. The framework sort of assumes that the game will continue during synchronization so there's no "complete" moment, it just sends everything continuously.

That's great, I'll try to get the PositionReplicator up in the next few days, it would be good to try out some other algorithms. The current one is okay but there's some noticeable jitter/rubber-banding.

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So I have completed the first stage of this now locally, the game now pauses when another client joins. Makes sure every client is synched, then resumes at the same time.

Here is a video

In this video I got a dumb actor that actually recieve no further network signals except for the initial synchronized state of position, speed and direction to move. Then it just bounces off the edge of the screen. All clients stay completely in synch.

All that is left is to add a default graphical interface to show the synch progress (currently only logged) and then a timer that shows the countdown to game unpausing.

Here is how the log looks on join,

[2020-06-10 00:29:24.249][548][SERVER] [LogBasicNetworkLobby::Info] Player joined UnkownPlayer with PeerID 1397867656
[2020-06-10 00:29:24.259][548][SERVER] [LogBasicNetworkLobby::Info] Player changed name to UnkownPlayer
[2020-06-10 00:29:24.525][565][SERVER] [LogGameSynchronizer::Info] Msec response number 1 from peer [1397867656] is 3866 local Msec is 62324
[2020-06-10 00:29:24.531][565][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] recorded a ping of 275
[2020-06-10 00:29:24.540][565][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] recorded a estimated msec of -58335
[2020-06-10 00:29:24.550][565][SERVER] [LogGameSynchronizer::Info] Estimated OS.GetTicksMsec offset for peer [1397867656] is -58335 based on 1 measurements
[2020-06-10 00:29:25.009][594][SERVER] [LogGameSynchronizer::Info] Peer [1018386675] completed synch
[2020-06-10 00:29:25.015][594][SERVER] [LogGameSynchronizer::Trace] All clients are not synched yet
[2020-06-10 00:29:25.025][594][SERVER] [LogGameSynchronizer::Info] Peer [1058880107] completed synch
[2020-06-10 00:29:25.031][594][SERVER] [LogGameSynchronizer::Trace] All clients are not synched yet
[2020-06-10 00:29:25.143][602][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] has synched 0 out of 120 nodes
[2020-06-10 00:29:26.611][690][SERVER] [LogGameSynchronizer::Info] Msec response number 2 from peer [1397867656] is 5153 local Msec is 64409
[2020-06-10 00:29:26.619][690][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] recorded a ping of 2063
[2020-06-10 00:29:26.631][690][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] recorded a estimated msec of -58245
[2020-06-10 00:29:26.636][690][SERVER] [LogGameSynchronizer::Info] Estimated OS.GetTicksMsec offset for peer [1397867656] is -58290 based on 2 measurements
[2020-06-10 00:29:26.641][690][SERVER] [LogGameSynchronizer::Info] Peer [1397867656] completed synch
[2020-06-10 00:29:26.652][690][SERVER] [LogGameSynchronizer::Trace] All clients synched, sending unpause signal
[2020-06-10 00:29:26.658][690][SERVER] [LogGameSynchronizer::Trace] Unpausing game in 2

If we look in the client log for the clients you can see the unpause signal reach them at different times,

[2020-06-10 00:29:26.777][267][PEER 1058880107] [LogGameSynchronizer::Trace] Unpausing game in 1.881
[2020-06-10 00:29:26.777][376][PEER 1018386675] [LogGameSynchronizer::Trace] Unpausing game in 1.891
[2020-06-10 00:29:27.094][275][PEER 1397867656] [LogGameSynchronizer::Trace] Unpausing game in 1.616

[PEER 1058880107] unpaused at 00:29:28.658
[PEER 1018386675] unpaused at 00:29:28.668
[PEER 1397867656] unpaused at 00:29:28.710

So even though there was over 700 ms difference in signal arrival all peers unpaused within 52 ms of each other. The only reason the last client is so far off is because it just joined and I still didn't make the server wait for a higher confidence on it's TickMsec value (if you see in the server log we only had 2 values, it is pretty accurate around 20). Which I probably will do in which case I assume all clients will unpause within 10 ms of eachother regardless of ping.

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