ROBLOX Vehicle

How ROBLOX Is Improving Its Network Physics

ROBLOX VehicleIf you drive a real-life car into a brick wall, the car doesn’t simply bounce back. With enough speed, it causes the brick wall to come crashing down in a destructive display of physics. (Just trust us on this.)

To make sure these kinds of things happen in ROBLOX, as in the real world, ROBLOX Senior Game Engine Developer Kevin He has made some improvements to ROBLOX’s distributed physics engine. Today, he’ll show us the improvements with a number of video demos.

Simulating Physics

Simulating physics – like a car colliding with a wall or a player character getting hit by a car – in a ROBLOX game with multiple players poses unique challenges. ROBLOX uses a distributed physics (DPhysics) engine, which divides the processing load among in-game players and the server hosting the game. The DPhysics engine scales well and keeps every player in sync with the action.

Each player has a “buffer zone” that determines the physics their computer processes. While this helps spread the processing load, we have recognized the room for improvement: for example, if a player “owns” some piece of a level within their buffer zone – let’s say they’re standing on a simple block – you might, in some cases, not be able to knock it over with a vehicle. The same holds true for a vehicle colliding with a player character. Instead of entering a “ragdoll” state, there are cases where the character remains standing.

Buffer Zones

Buffering Zones Before Fixes

The red balls indicate where players' simulation zones overlap.

This image shows an area we’re improving. There are four players clustered in the center of the level. Only the red balls are shared between the blue player and the other three players, and they’re far away. That means the other players can’t affect the objects in the blue player’s immediate vicinity.

This video shows the inconsistency in action. The vehicle can’t knock down the block “owned” by the other player or knock down the player. This is the result of an overly thin buffer zone between the players.

The Fixes

Buffering Zones After Fixes

Note the much larger shared buffer zones after the tweaks.

Our fixes tweak the buffer zones to create a softer edge; an overlap in who-controls-what. In other words, they make physics happen the way you’d expect.

This image shows the tweaked buffer zones for the purple player at the bottom. The number of red balls has dramatically increased, meaning much of the territory – most importantly, the common territory in the middle – is shared between all four players.

See It In Action

Watch this video to see how vehicles and characters respond under the tweaked DPhysics engine.

[do action=”youtube-iframe” videoid=”nISvYnB9NbE”/]

As this video shows, we’re also working on a new “ragdoll” state for the player character in ROBLOX. The ragdoll state simulates realistic body physics during an event like a car collision. It also works for projectiles, as previewed in this video:

[do action=”youtube-iframe” videoid=”WzI4eOojhJg”/]

The above is still work in progress. We’re interested in your feedback on the DPhysics and ragdoll changes we’re making to ROBLOX.

About Kevin He

Technical Director of Physics and Distributed Simulation at ROBLOX. @GongfuTiger on Twitter.

365 thoughts on “How ROBLOX Is Improving Its Network Physics

  1. West899

    Ugh, I Dont Like It, The Ragdoll Physics I Hate The Most, Its To Floppy Witch Makes War Game On ROBLOX Unbearable, And ROBLOX Shouldnt Need New Physics, Its A “GAME” It Is Just Fine The Way It Is.

  2. Lostrokk

    Might want to make the limbs ‘flop’ around a bit more. Maybe add a second joint to legs and arms?

  3. isaiah6996

    if a car hits a player the physics would seld the victom flying to death in this it causes the victom to fall work on realistic stuff

  4. poke114

    Ok, I like the wall collapse addition, but the ragdoll effect will ruin brickbattles because it would make weapons rediculously overpowered, and what makes ROBLOX special is how unrealistic it is.

  5. Anonymous

    I’m really looking forward to this! It’ll make roblox a WHOLE lot more realistic without players stopping cars.

  6. mybeach

    i love roblox and i think bilder man needs a big round of aplaws (CLAP)(CLAP)(CLAP)(CLAP)(CLAP)

    bilder man YOU ROCK!!!!

  7. kop

    I like this new physics! Maybe you could have an animation for when the character is sent flying in a ragdoll state, like waving arms and legs?

    P.S: If you cant cope with these awesome updates, then deal with it because games have to update or it gets boring. People say they will quit like a wuss if a certain update is put in, but you will quit anyway if nothing happens. Duh.

  8. elfacool

    I think that fixing the engine is a pretty good idea.And the ragdoll state is perfect currently a lot of places use scripts making it ragdollify the player but sometimes it results in a total fail, Arms fall , legs, and you’re immobilized.So this character state will make things simpler.

  9. Lightvvv

    Look…dont make roblox to realistic this is why alot of these games went down in the past cause they try to do stuff that makes no sence…I think try to keep it more blocky less realistic…

  10. Marioluigi35

    I like the rag doll collision, but i think it should have more use of the arms. If you get hit by a jeep, you just don’t FLOP over with your legs glued to your torso. In reality, your arms are being flung over in the air! That would make the player feel at least a little bit more realistic!

  11. rmbroblox

    I think the brick wall idea is great but not the getting hit by a car and falling over idea, there is somthing like that in the current ROBLOX jeep and i find it really annoying when people just come up to me and keep on ramming me untill i have to give up trying to stand up…

    1. Shedletsky

      What if, you, in RL, got hit by a car, you would go flying with your arms up! make that happen please?

      1. Marioh10

        That, is a good idea to me, but they should also make a call in the place where you can also make it be optional. :) Hoping this gets implemented still.

  12. johny52

    I think the ragdoll state should be like the ragdoll scripts that the community has made with Lua.

  13. Stiky2798

    *looks at new physics* HOLY-THIS IS AMAZING. Just add this to the game instead of the ridiculous Character Explorations stuff.

  14. rentor150

    its pretty good but you could have added the arms moving so its like he fell down! – rentor

  15. Jonman1705

    Roblox. This is horrible. I remember joining in 09. I loved the game because I could interact with my friends. Not because of this! I could get into a game instantly in 09. Now it takes about a minute. I hate the new graphics! I hate the new updates! I hate everything you’ve done past 2011. You’re ruining roblox. Not upgrading it. Improving it, or updating it. You’ve disgraced roblox entirely. You’ve disgraced video games. I’m only on roblox today for the very few good people in the community. There was a time when I wouldn’t get sworn at when I join a game!

    1. charlier21839


      I highly agree jon. They have ruined the game with updates and such. Look, A game is supposed to be a place where people can go and enjoy themselves. Not where a bunch of 2 yr olds run around like noobs! Why cant you understand Roblox! Why cant you feel for the player? Or is it all about BC? You know what, Im getting rid of mine. As soon as march ends. Roblox, Learn that a game is about the PLAYER not too much MONEY. I mean its good youre making a nice profit but dont flip over it. You ruined roblox admins. And as a consumer I have my opinion on this.

    2. TheEpicGum

      I agree entirely. I wasn’t in ROBLOX in 09, also known as the “Good ‘Ol days”. Currently, a lot of ROBLOX players are leaving and there is too much BC. I hope when the admins look at this that they decide to change ROBLOX back to the 09 version, delete BC, and make everyone happy. GO OLD ROBLOX!

      1. TheEpicGum

        By the way in my last post, I ment to say at the begining: “I wasn’t in 09, (also known as the Good ‘Ol Days) but I can it was the best.

    3. SwimyGreen

      At least they don’t post anything that has to do with gear on the blog now… The only things ingame that I really hate ae the new GUI with a gamebreaking reset tool. And also bodies. Most of those things are UGLY. Otherwise I still build as I enjoy it.

    4. GreenDayDude75

      2009 wasn’t anything special. I’m from 08 and I think this improves ROBLOX. The earlier years were special, yes, but now that games are getting better and more people are playing ROBLOX which means ROBLOX NEEDS improvement. You can’t cling to the past, just get over it like the rest of us.

    5. rainbowgirl500

      I mean,I sorta like the updates,But really! It seems like you cant go into a game with out noobs bothering you,you have to make rocket science to make an awsome game,And there is all the BC people,acting like NBC’s are dirt. What I would like to say is,what happened?

  16. ultimatecreatorA1

    Pretty nice. Like the way the character does ragdoll if you throw a dodgeball at it! ;)

  17. 1kaILIKEITcb7

    it looks cool and awsome, I like how d game looks, d shadows, d sun’s reflection, and other 3D effects. I also liked d physics, it looks more realistic than d current 1 especially how d body of d ppl reacts 2 d bump of d vehicle and d hitting force of d dodge ball.

  18. flynnanator

    I’m wondering when it will come out cant wait even that im starting to dislike ROBLOX and im moving onto minecraft because first i played club penguin then i got bored and played ROBLOX but now as im 13 i think minecraft is somthing im going to need to move onto

      1. Adog1201

        Club penguin was dah Bawmb!,
        Then I got bored of getting Membership, Moved onto Roblox, Been here since like.. Late LATE ’09, Now, -Puts on shades- Its time to Go mine.

  19. rockstar123rap

    I like this to be made here in Roblox, the dynamic lighting, the floating objects when on water, but please uprgrade the ragdoll state and when you swim or float in water. The car should have dents when crashed in the wall.

    1. Tidbit1

      Then, with that, you’re leaving ROBLOX and going into an extremely good grphiced, laggy game. We like keeping ROBLOX ROBLOX, and other games other games. The dynamic lighting and all, that’s updating ROBLOX, not changing it. When a ROBLOXian falls, their arms fly up; that’s what happens in the water. You fall, but the water is made to hold you. With no ground under you, you’re in the falling state, yet still above the water. The dents in the car would also be hard to do because the car is made of blocks. You could use a decal, but that might not look the best.

  20. thepro95

    i agree with ROBLOX. the game does need more realistic physics. ragdoll, good choice. cars driving through walls, even better choice. both are good. i also saw they said they were working on new Morphs and Faces for ROBLOX.


  21. unknown

    i must say it looks way way better like that cuz it looks real and if it real people will love it look at gta iv all the gta are old and not played more be cuz iv is realic

  22. ThecoolguyLOL

    This can get really annoying, though, in places like ROBLOX Building where there is a jeep.

  23. ds84182

    Why doesn’t the server process physics instead. If it did, all the client would do is update the blocks so they would be rendered.

  24. ziplocBag

    that is so cool! but i would like it if you didnt get pushed so fare away, then flop evrywere to get up. you should also remove the floping thing when you get up

  25. Joe Wama

    Maybe it’s possible to make the Roblox cars smoke up, and go on fire before they explode? And I see the player did not die when being ran over. Maybe you get man it so after a couple of times, they die?

  26. 888888Zombies

    Almost forgot! THE LIGHTING MUST (Yes, I meant MUST) BE IMPROVED! I hate being in a bright cave without anything to light up. That ruins the mood and pratically everything.

    1. SwimyGreen

      Oh yes please. I’ve been waiting for that since 2010. In fact I was waiting on building a place for it. I want a real flickering fireplace. That would be awesome.

      1. Marioh10

        Its called, fog color 0,0,0 and min. distance like 10 studs max 20. There is your “fix” if you wanted to start now…

  27. dork23232323

    Awesome But there is one flaw if use would use these phisics People could keep shooting people with it cuasing people to be unable to get up

  28. Rukiryo

    I’m for, and against this. While it is cool, ROBLOX is quite laggy at times, so this would most likely add to it. Instead of improving realism, improve the physics engine efficiency. Use the least amount of bits possible.

  29. Anonymous

    Dear,Fellow Robloxians,I think this is good but don’t u think that when u hit a car you should die or if car hits wall car explodes and brakes wall?

    1. SwimyGreen

      Couldn’t you just add that with Lua. Ex. If a car is oging a certain speed it kills a person. Or if a car comes in contact with a brick it expplodes. I’m just saying because not everybody ingame wants to die because of a fast collision.

  30. LordPicto

    Well, first off while fighting at a brick battle map wouldn’t it be detrimental to be flying around after being hit by a ball? That isn’t my favourite part of this, but if you won’t fly away that much it would be a bit more better.

  31. Quaint

    Cool, but if you are near an explosion, will you fly away ragdoll-like? That would make it more realistic.

    1. Dekot

      ROBLOX Studio -> Tools -> Test -> Server

      ROBLOX Studio -> Output -> Enter in out put: “game.Players:CreateLocalPlayer(1) wait(1) game.Players.Player:LoadCharacter(True)”

  32. josben

    cool! but i can’t build much i loved the search bar on the build mode but they took it of. and put some sets in,u can’t build much without the search bar.:(

  33. Teslobo

    I like the general idea. It needs a few more tweaks although I’m sure you are already doing so.

  34. megadeathkiller100 RBLX

    Add Less lag to roblox.
    And make it that Non-BC’s Get 5 robux every week.
    Build With a friend in one of ur games Also with studio mode build with friend, and also be able to chat.


      @megadeathkiller100RBLX – You are obviously a noob. If you’re gonna be a noob, go on the forums. If you do it on the RCB, it’s just overkill.

      @Original Topic – HOLY BLOX THIS IS AWESOME

    2. Marioh10

      I actually want to be able to do this, or atleast studio mode support for your own places in servers, because I need to do that if I want to save recorded roleplays for an alt. place…

  35. gust112

    thsi is stuff that mose of it you can aready do or that yo u can youse the tools there to do that so it dont matter on the tv yeah maybe a better tv would be a good idea

  36. Coulson8880

    Roblox all the stuff you are doing is geat you guys are doing a good job I like this game thanks

  37. pipnina

    well. Minecraft is different to ROBLOX. as Minecraft is a indie survival game. ROBLOX is a dumbed down game engine.


    ok first here the things i want done to roblox
    1.floating water
    3.make your own anything
    4.such as faces
    5.become admins
    7.To be more accurate on stuff
    to have webcam chat on party’s or chat have more tix or robux like 5 of either have floating houses on water
    like in the hack week whens that coming out have more exicting stuff have more people in a server be less laggy even on a slow computer have better modertors cuz for example if u said i dont like roblox and i like minecraft better youll get banned for one week thats what
    happened to me have more detail have lve tv on the tv’s you can buy
    so as in that if i changed to channel one on my real tv and you have a tv on roblox and you turn it on virtually itll go to the real channel and watch real tv have newspapers accutally having dates and news have a better video screen recorder have more tricks that you can do
    19.thats preety much it

    1. Tiny Girl-Beast


      I like the idea of the web came. That’d be epic..

      Anyways, it’s pretty cool, Andrew Haak, or if you’re the one who posted this.. O_O

    2. mbchris

      I totaly agree If You Agree Reply To Me Or JAKETORREZ4 Also they should put a ipad iphone ipod touch app!=D

    3. Marioh10

      ONLY thing I want related what you said, 2 is all I like out of what ya mentioned, and I SO WOULD LIKE VOICE CHAT FOR IT. -_- Seriously, I want voice chat on roblox so I do not always need FRAPS+STEAM for videos.

  39. superepicman23

    Are17 is right dont worry about that
    but… i really like that its good continue like that ROBLOX ;D you guys are better than minecraft

  40. Are17

    You guys need to start not worring about what Lego or what Minecraft is doing you need to start working on how to make roblox better don’t waste your time on developing roblox around those games people play roblox for what roblox is not because it’s like minecraft or Lego.

  41. crazyblox

    This would be great to add onto ROBLOX, as i have a racing game and when one kart goes into another, it acts as if it hit a really solid brick wall, not that great. But with kevin’s tweaks im sure it would make everything great.

    1. Roblox Trolls

      I don’t play ROBLOX because it’s like minecreaft, or any other game. I play roblox because it’s roblox. Period. So please. cut this NONSENSE out

    1. Kevin He

      It won’t affect gun bullets or sword touch that much. The former is too light and the latter is too slow. In general you need high speed and high impact objects to knock down a humanoid.

  42. Ebuild42(Pro-builder)

    As to say manythings need to be edited. such as water graphics to be put in a 4-D way as you would with a brick wall. Or such as a 4-D physics whirlpool. Or make it so that when you stab someone the sword goes into the person and comes out so thet it leaves a gash in the player.
    4-D physics are complicated and need time to be edited. But there are so many.

    1. PrinceKallie

      The world is NOT ready for 4D. We are still working out physics in the 3D world, let alone the 4D world. The only people who could understand 4D are physics geniuses.
      Or you got the idea of 4D wrong.

  43. CamoTamo

    You should add water physics, look at blender simulations for instance, wouldn’t that be great?

    1. HoneyBun

      Yeah. But I always want the water to spread by itself. I get tired of making it spread with Edit Mesh. It should spread on its own. It would look real cool!

  44. Alphadeath

    How would this work for swordfighters? I.E., lets say while swordfighting two players were to collide into each other at the same exact speed, would both said “players” fall down or would they both or only one of them die?

  45. alexluci

    Definitely a very good idea no doubt. But I have a feeling it could become annoying at times. For example the superball; when playing it would be very irritating to trip and fall everytime you get hit with a ball. I think the place owner should have the option to change it on/off in their game.

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