What can it do?
Lots of things! See the features page for an up-to-date list of the current features. Also, take a look at the screenshots page to see for yourself the kinds of eye candy OGRE can pump out.

Is OGRE A Game Engine?
No. OGRE can be (and indeed has been) used to make games, but OGRE is deliberately designed to provide just a world-class graphics solution; for other features like sound, networking, AI, collision, physics etc, you will need to integrate it with other libraries, something several frameworks have done, and we have a collision / physics reference integration library as an example in our distribution.

Why? Well, one reason is that not everyone who needs a 3D engine wants to make games, so we don't assume that you do - you can use OGRE for games, simulations, business applications, anything at all. Secondly, even within the games industry, requirements can vary widely; for
example a MMORPG will need a very different kind of network library than an FPS, and a flight sim will need a different kind of collision / physics system to fighting game. If OGRE included all these features, we would be enforcing a particular set of libraries on you, with an
inbuilt set of assumed requirements, and that's not good design. Instead, we provide a very integration friendly API and let YOU choose the other libraries, if you want them. Many experiened game developers have expressed their approval of this approach, because there are no
inbuilt constraints. It can be more daunting for newer users who just want to build another FPS-style game, but for those people there are a growing number of existing frameworks using OGRE which provide a complete solution using a given combo of libraries; but it's important
to realise that OGRE itself will always remain separate, flexible enough to be incorporated into any of these. The principle is of collaboration and integration with other libraries, rather than
assimilation of them, a standard tenet of component-based design.

Why should I consider using OGRE (rather than the other zillion 3D engines out there)?
Many other engines, whilst technically impressive, lack the cohesive design and the consistent documentation to allow them to be used effectively. Many of them have long features lists, but have the feel of a bunch of tech demos lashed together with twine, with no clear
vision to hold them together. Like any other software system this becomes their downfall as they become larger. Most other engines are also designed for one particular style of game or demo (e.g.
first-person shooters, terrain roamers).

OGRE is different. OGRE is design-led rather than feature-led. Every feature that goes into OGRE is considered throughly and slotted into the overall design as elegantly as possible and is always fully
documented, meaning that the features which are there always feel part of a cohesive whole. Quality is favoured over quantity, because quantity can come later - quality can never be added in retrospect. OGRE uses sound design principles learned, tried and tested many times
in commercial-grade software - the object-orientation mentioned in it's moniker is just one of those approaches - frequent use of design patterns is another. The core development team is kept deliberately small, and all of its members are veteren software engineers with many
years of real-world experience. Patches are welcomed from community, but they undergo a strict review for both quality and cohesion with the Ogre philosophy before being accepted.

OGRE does not assume what type of game or demo you want to make. It uses a flexible class hierarchy allowing you to design plugins to specialise the scene organisation approach taken to allow you to make any kind of scene you like. Want to render indoor levels fast? Fine, use the BSP/PVS plugin scene manager which has already been written. Want an outdoor landscape? Again, use another plugin scene manager. The rest of the engine continues to function exactly as before.

So the short answer is - if you favour design quality, flexibility and clear documentation, choose OGRE. You know it makes sense. ;)

Is it really free?
The Ogre source is made available under the GNU Lesser General Public License (LGPL), which basically means you can use it however you like as long as release the source for changes you make to the core engine if you distribute your product. The source to your application or to new plugins you create does not have to be released (although it would be nice if you did). See the licensing page for full licensing terms.