A couple of weeks ago I played (and finished)A Plague Tale, a game byAsobo Studio. I was really captivated by the game, not only by the beautiful graphics but also by the story and the locations in the game. I decided to investigate a bit about the game tech and I was surprised to see it was developed with a custom engine by a relatively small studio. I know there are some companies using custom engines but it's very difficult to find a detailed market study with that kind of information curated and updated. So this article.

Nowadays lots of companies choose engines likeUnreal orUnity for their games (or that's what lot of people think) because developing a custom AAA-level engine requires lots of resources, so, I decided to list here some of the most popular custom engines with the team-sizes and notable titles released with those engines.

Most of the engines listed here have been developed along the years with multiple iterations and multiple videogames, those engines have gone through several versions or even complete (or semi-complete) rewrites from scratch, with a consequent engine name change. Also, important to note, most of those engines use numerous middleware for specific functionalities (Platform, Physics, Network, Vegetation, UI, Rendering, Audio...).

*NOTE: I tried to be as much accurate as possible with the information about the employees count (I checked the companies websites, Wikipedia or company LinkedIn) but take it with a grain of salt (some employees numbers could not be up to date).

*From left to right: Assassin's Creed Odyssey, Final Fantasy XV, Red Dead Redemption 2

Below list is forvery big corporations, sometimes with complex corporate structures with several divisions (not only focused on videogames) and various studios/subsidiaries developing games. Some of them work with multiple engines, not only custom ones but also licensed ones.

Usually those companies invest in custom engines to have full control over the technology and also avoid the revenue cut imposed by the licensed engines. Despite that fact, there are some big companies that in the latest years have chosenUnreal Engine for their productions, the most notable cases are:

• Capcom is using Unreal for the new Street Fighter V title.
• Bandai Namco latest big hits are using Unreal: Jump Force, Dragon Ball Fighter Z, Dragon Ball Z: Kakarot, Tales of Arise.
• Square Enix also moved to Unreal for several new titles: Dragon Quest XI, Kingdom Hearts III, Final Fantasy VII Remake

It's interesting to see that those big three are Japanesse companies, I wonder if that's maybe a market trend for Japan. Also to note, the chinesse holdingTencent owns 40% ofEpic Games, I bet it has some influence in the Asian market.

*From left to right: Rise of the Tomb Raider, Uncharted 4, A Plague Tale

Here we have the medium-small companies that decided to create their custom technology for their titles.

The number of employees could be a nice reference to consider because a custom game engine isusually developed in-house (I mean, not outsourced) but note that some of those companies could have a big number of people due to in-house artist/audio teams, while other companies out-source those parts of the development.

It would be really nice to know how many engineers are working on the engine division for each company, I'm sure there would be some big surprises, probably by the low number of engineers working in the engine and tools!

Also interesting to know more info about the tooling included with those engines, it's really difficult to have access to that kind of information. Engines tooling is usually a hidden-secret (beside some GDC presentations or some quick showcase videos).

*From left to right: Horizon Zero Dawn, God of War, Death Stranding

Some observations from this list:

• Rise of the Tomb Raider listsonly 10 programmers working on Foundation engine in the credits, probably a good reference number to get an idea of the people working on the core engine.
• Kojima Productions use Decima engine, developed by Guerrilla Games, for Death Stranding, previously they used Fox Engine for Metal Gear Solid V.
• Media Molecule latest game/engine (Dreams) seems to have been developed by only~15 coders, amazing!
• Companies targeting one single platform, usually have less restrictions and can push the limits of that platform. Unfortunately, that's a luxury that most companies can not afford.
• Asobo Studio, the company that originated this market study is not that small... but, like other companies, they seem to work in multiple titles in parallel.
• Very nice to see that some of the engines have entries in the Wikipedia with some details and titles released, it should be a must.

*From left to right: The Witness, No Man's Sky, X-Morph Defense

Here we have some really small studios that also choose to develop a custom engine for their games. Note that most of those engines rely on other libraries/frameworks for certain parts of the game, the common choices we find areSDL (cross-platform graphics/input),OGRE (rendering engine),MonoGame (cross-platform game framework, also relyes onSDL, SharpDX, OpenTK, OpenAL-Soft...).

One question many people could ask is, what parts of the engine are actually coded by the developers? Well, it depends, but usually coders take care of thescreen-manager,entities-manager andcontent-manager as well as thewrappers/interfaces to the external libraries.

Second question, what parts of the engine usually rely on external libraries/middleware? It also depends on the company resources but usuallyaudio-system,physics,rendering,networking,ui-system,terrain-system,vegetation-system and some other pieces.

*From left to right: Factorio, Thimbleweed Park, Owlboy

On the following list (and the next one below) I added the publishing date (only +2012) and the link to Steam for all the games... there are not many games with custom engine from small studios out there and I think they deserve to be recognized and supported.

Some observations from this list:

• Nicolas Cannasse, co-founder of Shiro Games, is the the developer ofHaxe programming language andHeaps engine, used byMotion Twin forDead Cells (2017).
• Hello Games is a very small studio considering the size ofNo Man's Sky and that they use a custom engine. Really impressive!
• Runic Games was dissolved in November 2017, the founders created Double Damage, now they are working onEchtra Games on Torchlight III.
• Rodrigo Braz Monteiro, Chucklefish CTO, is the person in charge of Halley engine, actually the engine isopen-source!
• In most of those studios the people in charge of creating the game engine it's only 1-3 persons!
• Lo-fi Games was a one-man team (Chris Hunt) for more than 6 years!
• Some of the games in this list took +5 years of development!
• Not many games... a couple of hits per year...

*From left to right: Stardew Valley, ScourgeBringer, Eagle Island

Finally, the list of the heroes.

Games developed by 1-2 people with custom game engines, engines mostly coded by one person! Respect.

Creating an engine and a game from scratch to the point of publishing it is an extraordinary accomplishment, not many people in the world is ready for that.Almost all of them are 2D games, usually withvery small budgets and developed alongmultiple years. Congratulations to the developers!

*From left to right: Axiom Verge, Ghost 1.0, Remnants of Naezith

Some observations from this list:

• Some of those teams are formed by 1-2 people but probably grew at some point and/or outsourced some parts of the development (art, audio...). Usually the publisher also helps with some resources (localization, marketing...).
• Omar Cornut from Lizardcube is the main programmer for Wonder Boy: The Dragon's Trap engine and also the developer ofDear ImGui, a free and open-source immediate-mode gui library used by lots of AAA custom engines.
• Ben Fiquet from Lizardcube is also the main artist for Streets of Rage 4, the custom engine of Guard Crush Games is written by Cyrille Lagarigue.
• Marc Flury programmed Thumper game engine rejecting the OOP paradigm in favor of a procedural programming approach.
• Christian Whitehead is the creator of Star Engine used in Sonic Mania but Headcannon (Simon Thomley) and PagodaWest Games (Jared Kasl and Tom Fry) were also involved in the development of the game.
• Some of the games in this list took +5 years of development!
• Not many games... a couple of hits per year...

There are some other remarkable games using custom engines that worth mentioning:Minecraft (2011),Braid (2009),Super Meat Boy (2010),Terraria (2011),Dustforce (2012),Sword and Sorcery EP (2012),FEZ (2013),Dust: An Elysian Tail (2013),Rogue Legacy (2013),Dyad (2012),SpaceChem (2013),Darkest Dungeon (2016),Scrap Mechanic (2016),Battle Brothers (2015),Renowned Explorers (2015),Yuppie Psycho (2019),Surviving Mars (2018),The End Is Nigh (2017),The Binding of Isaac: Afterbirth (2017),The Binding of Isaac: Rebirth (2014),BattleBlock Theater (2013),Full Metal Furies (2017),Binding of Isaac (2011),Rusted Warfare (2017).

I'll start saying I'm biased, I'm really passionate about videogames-making technologies and I admire custom engines and game-making tools. I also contributed to custom engines ecosystem with my grain of salt:raylib andseveral game-making tools. I prefer a custom engine over a licensed one, I consider that the extra amount of effort put into the product usually translates into some specific great mechanic or some amazing in-game details.

Said that, I must admit that creating a custom engine is a big endeavour and not many people/companies are ready for that. I recognize Unity (and Unreal to less extend) have really democratized videogames development, lots of small-medium size companies can use Unity today to develop games quickly, sometimes, with very low budgets... But, still, lots of big companies prefer to rely on their own custom technologies.

From my gamedev-teacher perspective, I think students should learn how engines work internally with as much detail as possible. Relying only on engines like Unity/Unreal for education to allow students develop eye-candy project in short-time is not the way to go. At the end of the day, someone has to write the engine and the tools!

NOTE: Feedback and improvements are welcome! :)