95K views · Mar 11, 2019 · 59:38 · 4 HN recommenders · 6 mentions · discussed 2020–2025
A 2018 GDC talk by NetherRealm's Michael Stallone on the engine changes, optimizations and tooling needed to roll back and re-simulate up to 8 frames in 16 ms in Mortal Kombat and Injustice 2. It is a deep dive into deterministic rollback netcode.
Why Hacker News points people here: HN treats it as the definitive practical talk on rollback networking in a shipped AAA fighting game.
“For an in-depth explanation, see this excellent GDC talk on its implementation in Mortal Kombat and Injustice 2”HN comment, 2023
“this is a great GDC video to watch on the topic”
Great GDC talk on rollback networking.
Do you have a link to any blog posts, i would love to read about it. I tried to look on link , but development appears to be closed source? I'm just an outside observer, but i love the topic. For others like myself, this is a great GDC video to watch on the topic > 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2 this video
“Here's another great video on the subject”
Another great video on rollback networking.
Here's another great video on the subject: 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2 this video One of my favorite topics, partially because there's not that much literature on the subject but it's so important
“I really enjoyed this GDC talk on rollback networking”
Enjoyed GDC talk on rollback networking.
I guess it depends on how high a level you're looking at it from. Both lockstep and rollback are variants of the general approach of "shared deterministic simulation" where you're mostly just sending inputs. ("Mostly" 'cuz on reconnect or desync or whatever you'll probably want to send full state.) I really enjoyed this GDC talk on rollback networking: this video (From 2019.)
“For an in-depth explanation, see this excellent GDC talk on its implementation in Mortal Kombat and Injustice 2”
In-depth explanation of deterministic rollback in Mortal Kombat.
Specifically "Deterministic Rollback", as the clients don't wait for the server's response before displaying the change locally. For an in-depth explanation, see this excellent GDC talk on its implementation in Mortal Kombat and Injustice 2: this video
“the following videos are greatly entertaining deep dives into ludicrously technically complicated bugs or performance optimizations”
Entertaining technical deep dive among recommended GDC videos.
For those who aren't in the video game development field and like technical content, I cannot recommend watching GDC's content enough (even better, attending!). Although this blog post isn't as detailed as I've seen them do in the past, I appreciate that game developers have the opportunity to share their wins like this externally. If you enjoy watching technical content and video games, the following videos are greatly entertaining deep dives into ludicrously technically complicated bugs or performance optimizations done to deliver the gaming experience that I myself take for granted. - I Shot You First: Networking the Gameplay of Halo: Reach: link - 8 Frames in 16ms: Rollback Networking in Mortal Kombat and Injustice 2: this video - It IS Rocket Science! The Physics of Rocket League Detailed: link - link
“There is an amazing talk on this from the Mortal Kombat creators about how long it took them to get their netcode right[0].”
Talk on how long Mortal Kombat took to get netcode right.
I do indie game dev as a hobby, and I have taken multiple classes on networked multiplayer, and I've also implemented VERY SIMPLE proof of concepts for multiplayer fighting games in Unreal Engine. I think what a lot of people are missing here is the context that there is STILL not a "make it multiplayer" button in game engines. They do NOT do most of the work for you for any facet of game development. Making games is still a ton of work. To name a few things that Unreal Engine does not do for you: networked movement prediction, acceptable LERPing to positions when client/host disagree, anticheat... basically it has a nice client/server model API you can use. You can annotate structs to efficiently be transmitted over the internet, and query the API to see if you are "host" or "client". There is an amazing talk on this from the Mortal Kombat creators about how long it took them to get their netcode right[0]. Now make that much harder when dealing with millions of players in one world, with mold-able terrain and an exotic networking stack. 0: this video
