Gamers, Start Your Engines! 6 Top Gaming Engines Face Off
Middleware
While most of the heavy graphical lifting is relegated to full engines like the six we've already covered, more and more specialized processing and rendering is being offloaded to a variety of middleware utilities. Middleware is a broad term, and these mini-engines specialize in just about everything, from tree creation, to audio utilities, to physics modeling, to video compression. Here's a sampling of some of the most used middleware solutions used in game development.
SpeedTree
You might think virtual foliage creation tech is about as boring as watching virtual grass grow, but hey, trees are important. The nearly ubiquitous SpeedTree is a vegetation programming and modeling software that quickly generates a variety of semi-randomized foliage in real time. There’s also a SpeedTree Cinema version for higher resolution tree render libraries for use in feature films, including such titles as Avatar.

Havok Physics
The Havok Physics system has gone from a physics middleware to practically an engine unto itself. First released at GDC in 2000, it was bought in September 2007 by Intel, and was honored in 2008 at the 59th Annual Technology & Engineering Emmy Awards for advancing the development of physics engines in electronic entertainment. The Havok suite offers a full variety of separate processing modules, including Havok Physics, Havok Animation, Havok Behavior, Havok Cloth (soft body dynamics), Havok Destruction (rigid body environments), and Havok AI.

These physics and animation libraries are easily added to an existing engine. For example, Skyrim makes use of its own Creation Engine, but also takes advantage of Havok Physics, Animation, and Behavior libraries. Source's integrated physics engine is also based on modified Havok engine code.
PhysX
Nvidia's proprietary physics middleware solution, the main appeal of PhysX is its ability to offload complex physics processing tasks to the GPU. Of course, as an Nvidia technology, it's only available on Nvidia cards, though there is some software implementation of PhysX on consoles and some earlier PhysX titles.

PhysX provides impressive collision modeling for both hard bodies (terrain, debris, etc.) and soft bodies (cloth, hair, flesh). Proponents of the tech laud the improved realism and atmosphere, but naysayers question the dedicated hardware and processing power devoted to what's essentially an improved garbage and debris engine.
Scaleform

Another seemingly dry middleware, Scaleform does exactly what it says on the tin. A vector graphics rendering engine, Scaleform scales user interfaces, HUDs, and animated textures. This allows professional UI developers to design textual and graphical overlay elements in Adobe Flash and other native vector forms, and have them be scaled and fully interactive in games. So every time you see a game menu system that looks like it was ported over from an ill-conceived flash webgame, keep in mind that with Scaleform, that's actually a legitimate possibility. Scaleform is one of the most widely used middeware tools, and is also natively integrated into Unreal Engine 3 and Gamebryo.
Bink Video

One of the oldest legacy middleware apps, Bink Video is a proprietary video file format (.bik). Developed by RAD Game Tools, .biks are lightweight video files primarily used for full-motion video sequences in video games. Though not a low-quality algorithm by nature, unfortunately .biks are often highly compressed, mainly implemented in order to fit cinematics onto physical media. With digital distribution and larger optical media gaining favor, Bink has been in decline on PCs in recent years, but is still a major presence on mobile games.
Unigine
A middleware game renderer best known for its benchmarking capabilities, Unigine is actually secretly a full-on game engine in its own right. Unigine's claim to fame is its support of the most up-to-date API hooks and graphics tech available, supporting DirectX 11, OpenGL 4.0, and up to Shader Model 5.0. Its best known benchmarking tool, the Unigine Heaven DX11 benchmark also supports Nvidia 3D Vision and ATI Eyefinity.

Only 6,385 triangles? We demand our dragons have at least 10 thousand!