The Making Of Rocket League

“Supersonic Acrobatic Rocket-Powered Battle-Cars was a moderate success but the phrases ‘niche genre’ and ‘cult classic’ don’t exactly whet the appetites of people wanting to make money,” Jared Cone tells me. The lead gameplay programmer has agreed to talk about the making of Rocket League [official site] – its physics, its multiplayer, its tremendous success – but the difficulties start before the coding began, with the 2008 release of predecessor SARBC and its middling reviews and sales.

“There wasn’t an inkling of interest coming from anybody. That’s why Rocket League, like its predecessor, is completely self-funded,” says Cone. “We would do work-for-hire jobs to pay the bills while working on Rocket League in our free time and between contracts. It was difficult and the game had a low probability of ever releasing, but in the end it was probably for the better because we got to make the game we wanted to without having to cater to outside interests.”

Psyonix were free to chase the fun. Seven years and five million Rocket League downloads later, it looks like they caught it.

SARPBC has its roots in Unreal Tournament 2004’s Onslaught mode, for which Psyonix founder David Hagewood was drafted to prototype vehicle physics. Onslaught went down a treat, so rather than change tack, Psyonix opted to apply their vehicular expertise to a then unnamed racing game that pitted driver against obstacle, tacking on a rocket boosters as a means to control speed. But what’s more fun than smashing cars off static objects? As SARPBC’s Crash Course mode was to demonstrate, smashing cars off other cars and spoiling people’s days.

“That mode was so fun we decided to focus on it as the primary game,” Cone says. “We needed more game modes to appeal to publishers, so we started exploring what else we could do with these cars. Several prototypes were made until one day somebody decided to drop a ball into an arena to see how that played out. Even in its rough infancy the game was so fun that we yet again changed course to focus on it as the primary game. SARPBC and Rocket League were very much born out of ‘following the fun’.”

Alas, SARPBC was the product of a relatively new studio chock full of devs fresh from college (Cone himself joined with a flock of interns brought in to wrestle with SARPBC in its adolescence) and it struggled. To start, it was self-funded, and the money was gone; the marketing budget was buttons and fluff, and word of mouth wasn’t much of an option with YouTube in its infancy and Twitch non-existent. Psyonix wanted to remake SARPBC as soon as it released.

The initial concept behind Rocket League was a grand series of mini-games to test every aspect of automotive acrobatics in an open world. Cone still hopes to follow up that first pitch, but after their experience with SARPBC, Psyonix knew their best bet was to pick a single goal and nail it. That goal became scoring goals – using your leaping vehicles to steer a giant ball towards an opponent’s goal. Even this required multiple modes, however.

“We’ve always thought of the multiplayer as the most fun part of the game, but surprisingly the majority of people who bought SARPBC never played online – not even once. This meant we needed to have a more robust single-player experience for Rocket League, which is why we decided to focus on the Season mode instead of mini-games. The mini-games in SARPBC were fun and challenging, but for Rocket League we wanted players to spend time playing something that would train them and perhaps encourage them to play online.”

Of course, once Psyonix had figured out how to shepherd people into online matches, there was the small matter of forcing a real-time physics simulation to run in sync on up to six machines. The precursor to a solution was there in SARPBC, but Cone speaks of it like a war veteran reliving unspeakable things.

“Getting SARPBC somewhat playable over the internet was a terrible hack that didn’t even work all that well and continued to haunt me for years after its release,” he says. “In the back of my mind I was always thinking about how we could possibly get a high-speed rigid body physics game to play well with high latency. All multiplayer games with physics-based vehicles that I can think of don’t even try to deal with latency mitigation – they just have the client send its inputs to the server, wait for the server to run the physics simulation, then wait for the server to send the results back to the client. [But] Rocket League’s vehicles can turn on a dime, accelerate and brake extremely quickly, and have the ability to instantaneously change directions using jumps and dodges. Playing Rocket League without client-side prediction with just a 40 millisecond ping is uncomfortable. Playing with a 70+ millisecond ping is pretty much pointless.”

One of Psyonix’ other games helped point the way. “My work with client prediction on Nosgoth gave a lot of insight into how shooters handle client prediction for player characters,” continues Cone. “It’s a technique that’s been used by all shooters since the mid-90s. For Rocket League I had to extend the technique to work with a rigid body simulation instead of player characters, and to accommodate the client being able to predict vehicle movement while also properly interacting with the dynamic ball. There are issues with mispredicting other clients interacting with the ball, but overall I’m very pleased with how everything turned out.”

Nothing about the simulation is fudged. To achieve it, Psyonix had to integrate the Bullet physics engine with Unreal Engine 3’s PhysX, allowing them to reset the game state a few beats back in time and run up to a half-second catch-up simulation when things begin to desync. As an added bonus, Bullet offered much more control over suspension and friction than they were able to eke out of SARPBC.

In a way, Rocket League’s purity is misleading: under the surface of its early prototypes lurked a tangle of code that went far beyond telling the ball to bounce. Agile though Rocket League’s bumper cars are, the ball had to be upscaled to make it a practical target, with the unfortunate consequence of raising its centre of gravity relative to the vehicles. Hit a giant football with a regular jet-powered car and it’s some time before the ball returns from orbit. Psyonix had to integrate their own counter-forces to make the mutant ball behave, stepping through impacts frame by frame to spot problems in the logic.

“It seemed like every time a new problem was found, a new line of code would be added to our ball interaction logic to try to mitigate it,” Cone says. “After a while the code had grown from a nice simple three-line function to a monstrosity full of curves and scalars and branching logic. It got to the point where we couldn’t even debug the problems in the replay because we simply couldn’t follow the logic anymore. We found that adding more complication to the interaction just produced more unpredictable results. Eventually we decided to nuke all of our changes and start from a fresh perspective. Finally our consistency problems were solved with just a few minor tweaks to the original algorithm from SARPBC.”

Aside from glamorizing the sort of behind-the-scenes physics that typically gets relegated in reviews, Rocket League – and SARPBC by extension – is a remarkable confirmation of the cliché drilled into aspiring indies on a non-existent budget: one lean machine polished to perfection (and sometimes forced into shape with conviction) can carry you further than a loud, oversized muscle car. Roping in SARPBC veterans for a closed alpha, Psyonix were able to get experienced outside eyes on Rocket League’s less remarkable facets before release and buffed them into oblivion. It might simply be about booting balls into goals with supersonic automobiles, but Psyonix have iterated ceaselessly and continue to do so with the help of their players. The result is joy in motion, to watch as well as play – MLG’s inaugural Rocket League tournament ended with a heart-stopping overtime punt.

Far from letting the bright lights of esport-dom addle their brains, however, Psyonix’s next move seems measured and sensible: improved spectating and tournament support, bug fixes and a push into new countries. The rest, Cone says, is pretty much up to the community. The same scrupulous approach that tuned SARPBC into the honest, reliable Rocket League should keep it running for a very long time.

30 Comments

  1. Enkinan says:

    I finally bought into the hype and picked this up Friday. Then I bought it for my daughter and son as well and we stayed up till 2AM teaming up in 3v3 online matches.

    It’s just a great simple game.

  2. caff says:

    “SARPBC has its roots in Unreal Tournament 2004’s Onslaught mode, for which Psyonix founder David Hagewood was drafted to prototype vehicle physics.”
    Aha! This explains a lot about why I love Rocket League so much. UT2004 had incredible vehicle feel – the rocket cars are so similar to those with blades in UT2004 that I can’t believe I didn’t notice it sooner.

  3. Feet says:

    Love Rocket League, but does no one else remember the UT2K4 mod Carball? Here – link to youtube.com
    Played it quite alot back in the day, and it was really very similar.

    • Punk0 says:

      I remember the Carball mod well. Rocket League is a blatant ripoff of it. On the Psyonix forum there have been a couple posts about this. They say know the mod, but their 2 games have been influenced more by the Deathball mod for UT2K4. This has caused me to lose all respect for the developers. The game is almost a carbon copy of Carball, and almost nothing like Deathball. From the skill based rocket maneuvers, to the placement of the full boosts where the power ups were in Carball (on the soccer field map), the similarities are too much to ignore, and they should have just admitted where the idea came from. I don’t know the legality of the situation, since Carball was a mod for UT2K4 and probably wouldn’t have been made without using the existing game as the base. The only thing I feel is superior about Rocket League is the fact that it’s made for a controller and you no longer have to babysit the camera with the mouse.

      • A Rising Ape says:

        Well that’s just nonsensical, 90% of the history of games development is based on knocking off existing formulas and iterating better ones. The people who made those mods could have kept on with the concept and developed a standalone game of their own, but they didn’t, and so it passed into obscurity, where it would have remained if Psyonix hadn’t scooped the ball back up and rocketed all the way to the bank. That’s a tortured metaphor to be sure, but not as tortured as whatever logic you’re trying to use to make a mountain out of this rather sad molehill you have here.

        • sweetjer says:

          agreed, this notion of “you developed a game centered on an 11 year old mechanic, and I know you named an influence but you named the wrong one”… Can an idea be so half baked it’s burnt? I don’t think rocket league is being lauded for its brilliant new idea — it’s being lauded for executing a simple concept (hit ball into goal — but you’re in a car with rocket boosters) really well.

        • Punk0 says:

          So, if King had said, “We’re familiar with Bejeweled, but our inspiration for Candy Crush came from Tetris,” you’d be fine with that? They’d catch hell on the internet, and rightfully so. I never said they couldn’t make the game. I said they ripped of a mod, and when asked about it, they lied. Thus, the loss of respect.

          Carball wouldn’t have been an obscure mod if it had been released free to millions of subscribers on a system starved for good games. I’ve played the game. It’s good. In some ways it’s better than Carball, and in some ways not as good. I’m probably not as blown away by the experience as many of you because I’d been having it up until around five years ago, when 2 of the people I used to play with moved away. Carball has a higher skill ceiling, so I doubt I’ll be playing RB for years, like I did CB. Although RB currently has more players than CB ever had.

          I’m guessing you like the game, so you are going to defend the developer no matter what I say, but they should have just said something like, “We used to love Carball, and decided to update it for a new generation of gamers.” I realize that fewer people care about ethics in the business world, but I’m still one of them.

          • Bugamn says:

            You are problem making it a bigger problem than it is. Is it impossible that they have arrived at a very similar game through different means? And what is the ethical problem? Just because they haven’t admitted that Carball is very similar?

  4. tripwired says:

    Great game, great article. Surprising depth to a game of hitting a ball with your car, especially once you get a little experience under your belt and hit a few decent aerial shots – very addicting and rewarding.

    • MiniMatt says:

      +1 really lovely and interesting article; the charisma and passion of the interviewees shines through and the writer (and, one presumes, editor) have shaped a really engrossing story.

  5. ribby says:

    I just can’t see Rocket League as anything other than a very simplistic gimmicky game

    • ribby says:

      (sorry)

      • caff says:

        (grabs pitchfork)

      • Flit says:

        C’mon, you can’t throw out accusations like that without at least trying to back ’em up. It’s cool if the game’s not for you, but without humility or directed critique, you’re just whining!

        Rocket League caught me by surprise, I would have never bought it if my friend hadn’t insisted. I haven’t enjoyed a new multiplayer game this much in years.

    • fish99 says:

      So you played it and mastered it in mere seconds?

      • Xzi says:

        Doubt you’re gonna get an answer to that. The game is definitely not simple, and “gimmicky” is the weirdest label you could put on it. Does it use an Xbox Kinect or something? I don’t get it.

        • gunny1993 says:

          I dono, I think the game at it’s base counts as simple, it only has like 5 or 6 mechanics, but simplicity is one of its strongest points and from that simplicity comes massive complexity.

          Using simple as a pejorative is pretty dumb though, most of the best games in history as simple at their core, chess, poker etc rely on small easily understandable rule sets.

          • Premium User Badge

            MrPin says:

            And for that matter, football itself has no more than a few “mechanics”, and yet produces millions of unique situations. That’s what makes such games so beautiful!

  6. Lord Custard Smingleigh says:

    Very enjoyable read, I’d like to see more of these!

    Rocket League is a fantastic game because it has such a low requirement of skill to get started (driving around the pitch and ramming the ball is fairly easy) but there is so much subtlety to learn. Although I hate the phrase, “high skill cap” applies here.

    • Jac says:

      Agreed. All great games / spectator sports have this “quality”, football being the prime example.

  7. Rob Lang says:

    Excellent article. Enjoyed particularly Cone admitting to adding more code until unpredictable results before cutting it back and moving to old code.

    More of these please, RPS!

  8. Honigsenf says:

    carball is still a thing in MTA (beside SAMP its smaller gta san andreas multiplayer client). search in serverbrowser for “NEON” or “FFS”.Both communities have the mode available.

    • Punk0 says:

      Didn’t know Carball was made for MTA. I played it on UT2K4. 2 on 2 LAN play was some of the most fun I’ve ever had in multiplayer. I can see why people are drawn to Rocket League. I just wish it didn’t take being on PS Plus for the concept to finally catch on. I hope the creators of Carball have enjoyed some measure of success. The mod was free, and it gave me an my friends some amazing times.

  9. Scrape Wander says:

    It’s incredible how this little game, which I refer to lovingly as “Car Soccer” exclusively, got its hooks in me so definitively.

    I don’t really play competitive games with any regularity, but something about Car Soccer compels me each day to at least squeeze in a few matches. I’m halfway decent, somehow, after lots of practice.

    It’s not just that the simple idea is fantastic, it’s the little aesthetics in the game that are just incredibly designed. The weight of the ball, the energetic event of the goal, the upbeat and accessible soundtrack, the cuteness and severity of it all – this has snuck into my top 5 in 2015 list. And if you told me years ago I’d be saying that about this game I would’ve said you were crazy.

    • Flit says:

      “Car Soccer” is my title of choice as well :) . It’s a fun name, isn’t it? Even if it plays more like hockey…

  10. Premium User Badge

    Phasma Felis says:

    Does this game control like Nitronic Rush? It looks like it does, and I’ve been wishing for more of that sweet aerial acrobatic jazz.

    • Flit says:

      Have you played Distance, the follow up to Nitronic Rush?

      RL controls similar to Nitronic Rush/Distance on the surface, but in practice not really at all. RL has a double jump and no wings (shorter flights), the boost is way more powerful, there’s less friction (and handbrake is seperated into “power slide” & “brake”), and the average speed is slower.

      …and while I love the multi in Distance (lots of great community maps!), RL is a gosh dang masterpiece of competitive play.