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In computing, a game engine is the core software component of a computer game. It typically handles rendering and other necessary technology, but might also handle additional tasks such as game AI, collision detection between game objects, etc. The most common element that a game engine provides is graphics rendering facilities (2D or 3D).
Engines that only provide real-time 3D rendering are sometimes called 3D engines. Such engines include Genesis3D, Irrlicht, and Ogre. Many 3D engines are designed for other purposes, often in addition to games.
Overview
The term "game engine" arose in the mid-1990s, especially in connection with 3D games such as first-person shooters (FPS). Such was the popularity of id Software's DOOM and Quake games that rather than work from scratch, other developers licensed the core portions of the software and designed their own graphics, characters, weapons and levels—the "game content" or "game assets."
Later games, such as Quake 3 and Epic's 1998 Unreal were designed with this approach in mind, with the engine and content developed separately. The licensing of such technology has proved to be a useful auxiliary revenue stream for some game developers, as a single license for a high-end commercial game engine can range from $50,000 USD to $250,000 and the number of licensees reaching several tens of companies (for Unreal engine). At the very least, reusable engines make developing game sequels much easier and faster, a valuable advantage in the competitive computer game industry.
The continued refinement of game engines has allowed a strong separation between rendering, scripting, artwork, and level design. It is now common (as of 2003), for example, for a typical game development team to be composed of artists and programmers in an 80/20 ratio.
First-person shooter games remain the predominant users of third-party game engines, but they are now also being used in other genres. For example, the CRPG Morrowind and the MMORPG Dark Age of Camelot are based on the NetImmerse engine, the MMORPG Lineage II is based on the Unreal engine.
Middleware
SpeedTree forest-rendering middleware
Some companies now specialize in developing software suites known as "middleware." Middleware developers attempt to "pre-invent the wheel" by developing robust software suites which include many elements a game developer may need to build a game. Most middleware solutions provide facilities that ease development, such as graphics, sound, physics and AI functions. Some solutions only do one thing, such as render trees and plants, such as SpeedTree, but do it more convincingly than general purpose engines.
Some middleware contains full source code, others just provide an API reference for a compiled binary library. Some middleware solutions can be licensed either way, usually for a higher fee for full source code. The Gamebryo engine, for example, has the option of licensing it in either fashion.
Hobbyists
Game engine development is a popular project amongst computer science students, hobbyists, and game developers alike. It can require strong interdisciplinary understanding of geometry, color theory, and computing. Being largely visual, however, these developers consider it fun and rewarding. Crystal Space, for example, is a popular open source multiplatform game engine.
FPS Game Engines
The most well-known subset of game engines are 3D First-person shooter (FPS) game engines. Most of the groundbreaking development in terms of visual quality is done on FPS games. Even today, despite increasing realism of flight and driving simulators and real-time strategy (RTS) games, first-person shooters are still at the forefront in high-quality computer graphics.
The development of the FPS graphic engines that appear in games can be characterized by a steady increase in technologies, with some breakthroughs. Attempts at defining distinct generations lead to arbitrary choices of what constitutes a highly modified version of a 'old engine' and what is a brand new engine.
The classification is complicated as game engines blend old and new technolgies. Features considered advanced in a new game one year, become the expected standard the next year. Games with a mix of older generation and newer feature are the norm. For example Trespasser (1998) introduced physics to the FPS games, but it didn't became common until around 2002. Red Faction (2001) featured destroyable walls and ground, something not common in engines even in 2004. Codename Eagle (2000) added vehicle based combat to the usual FPS mix, something not added to the Unreal series until Unreal Tournament 2004 (2004).
Early FPS graphics engines
An Imp from
DOOM - a very simple pixelated sprite
1992-1995 Planar worlds (rectangular grid in Wolfenstein 3D, sector-based plane levels in Doom) with sprite objects. Hardware requirements: software (CPU) rendering.
The rise of 3D
Gunner from
Quake II - low-res texture skewed over a simplistic, crude 3D model
1996-1999. For the first time, game engines recreated true 3D worlds with arbitrary level geometry. Instead of sprites the engines used simply textured (single-pass texturing, no lighting details) polygon objects. Hardware requirements: first 3D-accelerators (Voodoo, Voodoo 2).
New capabilites, increasing detail
A Skaarj warrior from
Unreal 2 - a clever use of simply texture filtered and textured mapped polygons in plain light
2000-2003. New graphics hardware provided new capabilites, allowing new engines to add various new effects, such as particle effects, fog, coloured lightning, as well as increase texture and polygon detail. Many games featured large outdoor environments, vehicles, rag-doll physics. Hardware requirements: GeForce 2-4 (or similar).
The approach to photorealism
A Hell Knight from
DOOM 3 - rough self-shadowing and bump mapping, polygonal nature still apparent
2004-2006 (est.). Developers of this era of 3D engines often tout their increasingly photorealistic quality. The maps usually feature seemlessly integrated indoor-outdoor environments. Pixel shader-based textures, bumpmapping, vertex shaders used for animations, lighting and shadowing. Hardware requirements: GeForce FX (or other cards with shader support).
Titles marked with * are not released yet. Release dates are estimates.
The Future
Berserker from Unreal 3
technology demo - thanks to extremely detailed model, advanced bump-mapping, real-time soft self-shadowing it has nearly "pre-rendered cinematic" quality
According to Epic Games, games based on Unreal 3 engine can be expected around 2006. These games are likely to include some of the technology showcased in existing technology demos (including those from graphics card manufacturers), including realistic shader-based materials with predefined physics, environments with procedural and vertex shader-based objects (vegetation, debris, human made objects such as books or tools) universally destructible and interactive levels, procedural animation, cinematographic effects (depth of field, motion blur, etc.), realistic lighting and shadowing.
John Carmack, the lead programmer for id Software, has repeatedly stated his opinion that it will likely be possible by 2010 to do a real-time video-realistic rendering of a static real-world-like environment. According to development plans announced by id Software, their second next 3D engine may attain such capabilities.
See also
External links
- 3D Engines Database (http://www.devmaster.net/engines/), a comprehensive database of today's graphics and game engines
- Terrain in Games (http://www.vterrain.org/Games/), an extensive overview of terrain rendering in 1997-2000 game engines
- IDV's SpeedTree website (http://www.idvinc.com/html/product_browser.htm)
- Great Game Graphics... Who Cares? (http://www.gdconf.com/archives/2003/Rubin_Jason.ppt) Includes overview of graphics devlopment in video games till 2003 (Powerpoint)
zh-cn:游戏引擎
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