History of Game Engines: id Tech, Unreal, Unity and Godot
How game engines emerged and evolved, from id Tech behind Doom and Quake to Unreal Engine, Unity and open-source Godot, with key dates along the way.
Today, making a game usually starts with deciding which engine to use. The engine handles common features like the renderer that draws the screen, physics, sound, input and animation, and developers build their game's unique rules and content on top of it. But it wasn't always this way.
In this post we look at how the concept of a game engine came about, why id Software's engines are seen as the starting point, and what trends Unreal, Unity and Godot each created. At the end, we briefly sum up a few things to consider when choosing an engine.
Before Engines: Every Game from Scratch
Most games in the 1970s and '80s were standalone programs. On machines like the Atari 2600, the way graphics were drawn was tightly bound to the hardware, so developers had to write code from the ground up to suit each machine's quirks. Memory was so small that keeping a general-purpose structure was close to a luxury. Arcade hardware also changed quickly, making it hard to carry one game's code over to the next.
Still, the seeds of reuse were there. Nintendo used the smooth side-scrolling technology it built for Excitebike (1984) in Super Mario Bros. (1985). In-house systems such as Sierra's AGI and LucasArts' SCUMM also appeared, allowing several adventure games to be built on the same foundation. However, these systems were mostly used only within each company and weren't sold to others as products.
id Software and the Birth of the "Engine"
The term "game engine" came into wide use in the mid-1990s, when first-person shooters were booming. id Software was at the center of it.
- Wolfenstein 3D (1992): Used raycasting to create spaces that looked 3D, and the engine was licensed to other companies.
- Doom (1993): The Doom engine built by John Carmack made a big impact with its varying floor heights and lighting. Because it separated game rules from data, other developers could license the engine and add their own weapons, characters and maps.
- Quake (1996): Achieved true real-time 3D graphics and introduced a client-server architecture and a game scripting language called QuakeC.
The engines behind Quake II, Quake III Arena (1999) and Doom 3 (2004) were later retroactively named id Tech 2, 3 and 4. The id Tech name itself was coined in 2007 when id Tech 5 was unveiled. GoldSrc, a heavily modified Quake engine, powered Valve's Half-Life, and this lineage continued with the Source engine released alongside Half-Life 2 in 2004.
Another hallmark of id Software is that it has released the source code of its older engines. Engines up to id Tech 4 were released under the GNU GPL and became the basis for countless modified versions and learning resources. However, since being acquired by ZeniMax Media in 2009, id has not licensed id Tech 5 or later engines externally, using them only for its own and sister studios' games. id Tech 8, used in Doom: The Dark Ages (2025), is the first id Tech engine to require a graphics card with ray tracing support.
Unreal Engine: The Standard for Engine Licensing
Epic Games' Tim Sweeney began developing an engine for Unreal (1998) in 1995. Unreal Engine was designed from the start with licensing to other studios in mind, and in the 2000s it secured far more licensees than id Tech.
| Generation | Period | Key changes |
|---|---|---|
| UE1 | 1998 | Software and early 3D accelerator rendering |
| UE2 | First game in 2002 | Hardware rendering focus; PS2, Xbox and GameCube support |
| UE3 | First game in late 2006 | Multithreading; based on DirectX 9 |
| UE4 | First game in 2014 | Physically based materials; Blueprint visual scripting |
| UE5 | Full release in 2022 | Nanite (virtualized geometry), Lumen (dynamic global illumination) |
In Korea, Lineage II is often cited as a prominent example of a game built with Unreal Engine 2.
UE4 marked a major shift in Unreal's business model. Instead of selling the engine for a large upfront fee, Epic switched to letting anyone download and use it for free, paying royalties once their game earns revenue. Today the royalty is 5% on revenue above $1 million, and games released exclusively on the Epic Games Store are exempt. The source code is also available on GitHub.
Unreal has spread beyond games, too. The series The Mandalorian used virtual production, displaying real-time Unreal backgrounds on LED walls during filming, and the technique has since spread to many other film and TV productions.
Unity: Democratizing Game Development
Unity was first announced as a Mac OS X engine at Apple's Worldwide Developers Conference (WWDC) in June 2005. Its stated goal was to "democratize" game development—to build tools that small teams could use without expensive licenses.
Mobile was what drove Unity's big growth. When Apple's App Store opened in 2008, Unity supported the iPhone, and with Android support in Unity 3 in 2010, it became the leading engine for mobile game development. In a 2012 Game Developer magazine survey, it was named the top engine for mobile platforms. Pokémon GO, Monument Valley, Cuphead and Beat Saber were all made with Unity.
Unity's strengths can be summed up as follows:
- C# scripting and a relatively approachable editor keep the barrier to entry low.
- It supports a wide range of platforms: mobile, PC, consoles, web, and VR/AR.
- With a large Asset Store and plenty of learning resources, you're relatively less likely to get stuck on your own.
There were setbacks, too. In September 2023, Unity announced a "Runtime Fee" that charged based on the number of installs, sparking fierce backlash from developers. It released a revised plan with relaxed terms, but trust issues lingered, and in September 2024 Unity scrapped the Runtime Fee entirely. In October of that year, it released Unity 6, returning to numbered version names instead of years.
Godot: The Rise of an Open-Source Engine
Godot is an engine created by Argentine developers Juan Linietsky and Ariel Manzur. Used from around 2001 as an in-house engine for South American companies, it was open-sourced under the MIT License in 2014. The name comes from Samuel Beckett's play Waiting for Godot, reportedly reflecting the idea of a never-finished project that keeps adding features.
Here's how things have unfolded since it went open source:
- December 2014: Version 1.0 released
- 2018: Version 3.0 released, adding a physically based renderer and C# support (developed with a grant from Microsoft)
- 2020: Received a $250,000 grant from Epic Games
- March 2023: Version 4.0 released with a completely overhauled Vulkan-based renderer
Godot has no licensing fees or royalties at all, and the engine itself is lightweight. Thanks to its structure of combining nodes and scenes and its Python-like GDScript, it's especially popular for 2D games and small projects. During Unity's 2023 pricing controversy, some developers moved to Godot, raising its profile considerably, and Re-Logic, the developer of Terraria, pledged donations to Godot. One limitation is that its open-source license is incompatible with console SDKs, so console releases must go through third-party companies.
Other Engines and In-House Engines
Beyond these three, many other engines have shaped the industry.
- CryEngine: The engine Germany's Crytek used for Far Cry (2004) and Crysis (2007), famous for cutting-edge graphics at the time. Amazon built Lumberyard on it, which in turn led to the open-source engine O3DE.
- Source engine: Used in Valve's Half-Life 2, Portal, Left 4 Dead and more, and succeeded by Source 2 in 2015.
- RenderWare and Gamebryo: Middleware engines used in the GTA series, The Elder Scrolls III: Morrowind and others in the 2000s.
Large companies still often use in-house engines. They can be optimized precisely for the company's own games and aren't affected by outside policy changes, but they're costly to maintain. In fact, some studios, such as CD Projekt, have dropped their in-house engines and moved to Unreal.
Things to Consider When Choosing an Engine
There's no single right answer, but you can usually narrow it down with the criteria below.
| Criteria | Unreal | Unity | Godot |
|---|---|---|---|
| Strengths | High-quality 3D, large projects | Mobile and multiplatform, abundant resources | Lightweight, completely free, 2D |
| Main languages | C++, Blueprint | C# | GDScript, C#, C++ |
| Cost structure | Royalties above a revenue threshold | Subscription plans | None |
It's practical to weigh team size, target platforms, graphical ambitions and the languages your team already knows. Since engine pricing policies can change, it's best to check the latest terms in the official documentation before you start.
KEKE STUDIO makes its games with Unity. For a small team that needs to ship the same game across multiple platforms with a focus on mobile, Unity's broad platform support is a good fit.