OGRE
OGRE Object-Oriented Graphics Rendering Engine) is a scene-oriented, flexible 3D rendering engine (as opposed to a game engine) written in C++ designed to make it easier and intuitive for developers to produce applications utilizing hardware-accelerated 3D graphics. The class library abstracts the details of using the underlying system libraries like Direct3D and OpenGL and provides an interface based on world objects and other high level classes.
As its name states, OGRE is "just" a rendering engine. As such, its main purpose is to provide a general solution for graphics rendering. Though it also comes with other facilities (vector and matrix classes, memory handling, etc.), they are considered supplemental. It is not an all-in-one solution in terms of game development or simulation as it doesn't provide audio or physics support, for instance.
Generally, this is thought of as the main drawback of OGRE, but it could also be seen as a feature of the engine. The choice of OGRE as a graphics engine allows developers the freedom to use whatever physics, input, audio and other libraries they want and allows the OGRE development team to focus on graphics rather than distribute their efforts amongst several systems. OGRE explicitly supports the OIS, SDL and CEGUI libraries, and includes the Cg toolkit.
As of version 1.7.0 Ogre is claimed to be released under the terms of the MIT License but the actual license text used is significantly modified. Earlier versions of OGRE was published under a dual license (one being LGPL, the other one called OGRE Unrestricted License (OUL)), to make it possible to be chosen for console development as well, because for most of the publishers copyleft license terms are unacceptable.
OGRE has an object-oriented design with a plugin architecture that allows easy addition of features, thus making it highly modular.
OGRE is a scene graph based engine, with support for a wide variety of scene managers, most notably octree, BSP and a Paging Landscape scene manager, along with a beta-stage portal-based scene manager under ongoing development.
OGRE is fully multi-platform, with OpenGL and Direct3D support. It can render the same content on different platforms without the content creator having to take into consideration the different capabilities of each platform. This reduces the complexity of deploying a game on multiple systems. Currently pre-compiled binaries exist for Linux, Mac OS X, and all major versions of Windows. OGRE also supports Vertex and Fragment programs along with custom shaders written in GLSL, HLSL, Cg and assembler.
The landscape scene manager has support for Progressive LOD, which can be automatically or manually created.
The animation engine has full support for hardware weighted multiple bone skinning, which can be fixed across several poses for full pose mixing.
OGRE also has a compositing manager with a scripting language and full screen Video post-processing for effects such as HDR, blooming, saturation, brightness, blurring and noise. A particle system with extensible rendering and customizable effectors and emitters.
The libraries also feature memory debugging and loading resources from archives.
There are content exporter tools available for most 3D modelers around including 3D Studio Max, Maya, Blender, LightWave, Milkshape, Sketchup and more.
A full overview of the features provided by OGRE can be found the OGRE3d website.
