Unreal Engine

The first-generation Unreal Engine was developed by Tim Sweeney, the founder of Epic Games.[3] Having created editing tools for the shareware games ZZT (1991) and Jill of the Jungle (1992),[4] Sweeney began writing the engine in 1995 for the production of a game that would later become a first-person shooter known as Unreal.[5][6] After years in development, it debuted with the game's release in 1998,[7] although MicroProse and Legend Entertainment had access to the technology much earlier –licensing it in 1996.[8] According to an interview, Sweeney "wrote 90 percent of the code in the engine."[9]

A screenshot of the first version of UnrealEd, displaying an user interface written in Visual Basic.[8]

Among its features were collision detection, colored lighting, and a limited form of texture filtering.[10] The engine also integrated a level editor, UnrealEd,[11] that had support for real-time constructive solid geometry operations as early as 1996, allowing mappers to change the level layout on the fly.[12][13] Even though Unreal was designed to compete with id Software, developers of Doom and Quake, the game was praised by John Carmack for the use of 16-bit color and the implementation of ambient effects such as volumetric fog. "I doubt any important game will be designed with 8-bit color in mind from now on. Unreal has done an important thing in pushing toward direct color, and this gives the artists a lot more freedom," he said in an article written by Geoff Keighley for GameSpot. "Light blooms [the spheres of light], fog volumes, and composite skies were steps I was planning on taking, but Epic got there first with Unreal."[6] Another notable feature was the introduction of real-time direct illumination in 1995.[14]

At first, the engine relied completely on software rendering, meaning the graphics calculations were handled by the CPU.[3] However, over time, it was able to take advantage of the capabilities provided by graphics cards, a process that required Sweeney to rewrite the core rendering algorithm several times.[13] As a result, software and hardware rendering would coexist in the engine, with the latter focusing on the Glide API, specially designed for 3dfx accelerators.[10] While supported, OpenGL and Direct3D reported a slower performance compared to Glide due to their deficiency in texture management.[15][16] With regard to audio, Epic employed the Galaxy Sound System, a software programmed in assembly language that integrated both EAX and Aureal technologies and allowed the use of tracker music, which gave level designers flexibility in how the soundtrack was played at a specific point.[17][18][19]

Epic's Unreal was noted for its technical innovations, but Sweeney recognized that the game underachieved in other aspects, with high system requirements and online gameplay being the most criticized parts by players.[20] The development of Unreal Tournament enabled Epic to address these points, incorporating several enhancements in the engine intended to improve the networking code and stability while refining the artificial intelligence to allow bots to demonstrate coordination in team-based environments.[21] In addition to being available on Microsoft Windows, Linux, Mac and Unix,[22] the engine was ported through Unreal Tournament to PlayStation 2 and, with the help of Secret Level, to Dreamcast.[23][24]

By late 1999, The New York Times indicated that there had been sixteen external projects using Epic's technology, including Deus Ex, The Wheel of Time, and Duke Nukem Forever,[22] the latter of which was set to debut the Duke Nukem series on the GameCube console.[25] Unlike id Software, whose engine business only offered the source code, Epic provided technical support for licensees and met with them to discuss improvements to its game development system.[8][26] While it cost around $3 million to produce and licenses for up to $350,000,[22] Epic gave players the ability to modify its games with the incorporation of UnrealEd and a scripting language called UnrealScript, sparking a community of enthusiasts around a game engine built to be extensible over multiple generations of games.[27][28][29][30]

The big goal with the Unreal technology all long was to build up a base of code that could be extended and improved through many generations of games. Meeting that goal required keeping the technology quite general-purpose, writing clean code, and designing the engine to be very extensible. The early plans to design an extensible multi-generational engine happened to give us a great advantage in licensing the technology as it reached completion. After we did a couple of licensing deals, we realised it was a legitimate business. Since then, it has become a major component of our strategy.

— Sweeney, Maximum PC, 1998[30]

Killing Floor was built in Unreal Engine 2.

In October 1998, IGN reported, based on an interview with affiliate Voodoo Extreme, that Sweeney was doing research for his next-generation engine.[31] With development starting a year later,[22] the second version made its debut in 2002 with America's Army, a free multiplayer shooter developed by the U.S. Army as a recruitment device.[32][33] Epic would later release Unreal Championship on the Xbox, with it being one of the first games to utilize Microsoft's Xbox Live.[29]

Though based on its predecessor, this generation saw a notable advance in rendering terms and new improvements to its tool set.[34] Besides a completely rewritten renderer, capable of running levels nearly 100 times more detailed than those found in Unreal, the engine was updated to include a variety of features, including a skeletal animation system, which was showcased in the PlayStation 2 version of Unreal Tournament, the Matinee cinematic editing tool, particle systems, and export plug-ins for 3D Studio Max and Maya.[34][35][36] Additionally, the framework for UnrealEd was rewritten in C++ using the wxWidgets toolkit, which Sweeney said was the "best thing available" at the time.[8]

Physical simulations, such as ragdoll player collisions and arbitrary rigid body dynamics, were powered by the Karma physics engine.[36][29] With Unreal Tournament 2004, vehicle-based gameplay was successfully implemented, enabling large-scale combat.[29][37] While Unreal Tournament 2003 had support for vehicle physics through the Karma engine, as demonstrated by a testmap with a "hastily-constructed vehicle", it wasn't until Psyonix created a modification out of Epic's base code that the game received fully coded vehicles. Impressed by their efforts, Epic decided to include it in its successor as a new game mode under the name of Onslaught by hiring Psyonix as a contractor.[36][38][39] Psyonix would later develop Rocket League before being acquired by Epic in 2019.[40]

A specialized version of UE2 called UE2X was designed for Unreal Championship 2: The Liandri Conflict on the original Xbox platform, featuring optimizations specific to that console.[41] In March 2011, Ubisoft Montreal revealed that UE2 was successfully running on the Nintendo 3DS.[42]

Screenshots of Unreal Engine 3 were presented in 2004, at which point the engine had already been in development for over 18 months.[43] Because of the modular nature of Epic's technology, Unreal Engine 3 contains code from the first-generation. "The basic architectural decisions visible to programmers of an object-oriented design, a data-driven scripting approach, and a fairly modular approach to subsystems still remain [from Unreal Engine 1]. But the parts of the game that are really visible to gamers –the renderer, the physics system, the sound system, and the tools– are all visibly new and dramatically more powerful," said Sweeney.[44] Unlike Unreal Engine 2, which still supported a fixed-function pipeline, Unreal Engine 3 was designed to take advantage of fully programmable shader hardware.[44] All lighting and shadowing calculations were done per-pixel, instead of per-vertex. On the rendering side, Unreal Engine 3 provided support for a gamma-correct high-dynamic range renderer.[44] The first games released using Unreal Engine 3 were Gears of War for Xbox 360, and RoboBlitz for Windows, which were both released on November 7, 2006.[45]

Screenshot of the Samaritan demo

Initially, Unreal Engine 3 only supported Windows, PlayStation 3, and Xbox 360 platforms, while iOS (first demonstrated with Epic Citadel) and Android were added later in 2010, with Infinity Blade being the first iOS title and Dungeon Defenders the first Android title.[46][47] In 2011, it was announced that the engine would support Adobe Flash Player 11 through the Stage 3D hardware-accelerated APIs and that it was being used in two Wii U games, Batman: Arkham City and Aliens: Colonial Marines.[48][49] In 2013, Epic teamed-up with Mozilla to bring Unreal Engine 3 to the web; using the asm.js sublanguage and Emscripten compiler, they were able to port the engine in four days.[50]

Throughout the lifetime of UE3, significant updates were incorporated,[51] including improved destructible environments, soft body dynamics, large crowd simulation, iOS functionality,[52] Steamworks integration,[53] a real-time global illumination solution,[54][55] and stereoscopic 3D on Xbox 360 via TriOviz for Games Technology.[56][57][58] DirectX 11 support was demonstrated with the Samaritan demo, which was unveiled at the 2011 Game Developers Conference and built by Epic Games in a close partnership with NVIDIA, with engineers working around the country to push real-time graphics to a new high point.[59][60][61]

While Unreal Engine 3 was quite open for modders to work with, the ability to publish and sell games meant using UE3 was restricted to licensees of the engine. However, in November 2009, Epic released a free version of UE3's SDK, called the Unreal Development Kit (UDK), that is available to the general public.[62]

In December 2010, the kit was updated to include support for creating iOS games and apps.[63] OS X support followed in the September 2011 release.[64]

Development on Unreal Engine 4 began in 2003, according to Mark Rein, the vice-president of Epic Games.[65] In early 2008, Sweeney revealed in an interview that he was basically the only person working on the engine, although he stated the development team would expand over time, designing the engine in parallel with the efforts by the UE3 team.[66] In February 2012, Rein said "people are going to be shocked later this year when they see Unreal Engine 4";[67] Epic unveiled UE4 to limited attendees at the 2012 Game Developers Conference,[68] and a video of the engine being demonstrated by technical artist Alan Willard was released to the public on June 7, 2012 via GameTrailers TV.[69]

One of the major features planned for UE4 was real-time global illumination using voxel cone tracing, eliminating pre-computed lighting.[14] However, this feature, called Sparse Voxel Octree Global Illumination (SVOGI), has been replaced with a similar but less computationally expensive algorithm due to performance concerns.[70] UE4 also includes the new "Blueprints" visual scripting system (a successor to UE3's "Kismet"[71]), which allows for rapid development of game logic without using code, resulting in less of a divide between technical artists, designers, and programmers.[72][73]

I could say: 'I'm going to convert this pillar into a blueprint [in the Engine] and add some sort of trap to it.' It means I can really go in and start enhancing my world with interaction that just would not have been possible without a technical artist, a designer and a programmer and now any one of those three can do all of it, provided they have the assets handy. The fact that I can just go in and say, 'If you're within X distance of this thing, start to glow and take my distance to it, normalize it zero to one and then just lerp [oscillate] between two different brightness values, so as I reach for something it gets hot'...that would have been something do-able but very difficult for anybody except a gameplay programmer. And he wouldn't have known how to set up the assets, but now any one of the three could do it.

— Willard, Kotaku, 2012[73]

On March 19, 2014, at the Game Developers Conference (GDC), Epic Games released Unreal Engine 4 through a new licensing model. For a monthly subscription at US$19, developers were given access to the full version of the engine, including the C++ source code, which could be downloaded via GitHub. Any released product was charged with a 5% royalty of gross revenues.[74] The first game released using Unreal Engine 4 was Daylight, developed with early access to the engine[75] and released on April 29, 2014.[76]

On September 4, 2014, Epic released Unreal Engine 4 to schools and universities for free, including personal copies for students enrolled in accredited video game development, computer science, art, architecture, simulation, and visualization programs.[77] On February 19, 2015, Epic launched Unreal Dev Grants, a $5 million development fund aiming to provide grants to creative projects using Unreal Engine 4.[78]

An Unreal Engine booth at GDC 2017

In March 2015, Epic released Unreal Engine 4, along with all future updates, for free for all users.[79][80] In exchange, Epic established a selective royalty schedule, asking for 5% of revenue for products that make more than $3,000 per quarter.[81] Sweeney stated that when they moved to the subscription model in 2014, use of Unreal grew by 10 times and through many smaller developers, and believed that they would draw even more uses through this new pricing scheme.[82]

In an attempt to attract Unreal Engine developers, Oculus VR announced in October 2016 that it will pay royalty fees for all Unreal-powered Oculus Rift titles published on their store for up to the first $5 million of gross revenue per game.[83]

To prepare for the release of its free-to-play "Battle Royale" mode in Fortnite in September 2017, Epic had to make a number of Unreal Engine modifications that helped it to handle a large number (up to 100) of connections to the same server while still retaining high bandwidth, and to improve the rendering of a large open in-game world. Epic said it would incorporate these changes into future updates of the Unreal Engine.[84]

With the opening of the Epic Games Store in December 2018, Epic will not charge the 5% revenue fee on games that use the Unreal Engine and released through the Epic Games Stores, absorbing that cost as part of the base 12% cut Epic is taking to cover other costs.[85]