Hi,
They both are good graphics engines with excellent documentation and helpful communities. Neither engine is a game engine: alone these libraries only cater for graphics.

To me, the choice of one graphic engine boils down to personal preference.

Irrlicht has a little less features than Ogre 3D straight out of the box (though you can easily expand Irrlicht to add more features). But it is completed by other toolsets:
- a 3d world editor (irrEdit)
- a 2d and 3d sound engine (irrKlang)

As a lone programmer, I prefer Irrlicht because of its available toolsets which let me focus on realizing a game. When I started with Irrlicht a few years ago, it had a simpler interface than Ogre 3D. I do not know if it is still true today as Ogre 3D also improved its interface.

For my games, I use Irrlicht for graphics, Irrklang for sound (though it can be replaced by another sound library), SFML for network management and multithreading interface. Note that most of my time is not spent in programming, but creating the resources for a game (especially in turn based wargames). This is why I favored simple interface and existing toolsets.

Hope that helps,

Ghostly yours,
Red.

What really is the difference between say Irrlicht and OpenGL?
And what would you use to implement physics?

Hi,

1) Irrlicht vs OpenGL
OpenGL is a graphics library. It provides low level functions for displaying 3D graphics. Implementing effects, model loading and display, organizing the scene is the responsability of the developper. Irrlicht is a graphics engine which provides high level functions to display effects, load and animate models, display a scene. Irrlicht is built on top of a graphic library (even 3 as it let you choose between 3 underlying graphics libraries : OpenGL, DirectX or a software emulation).

2) Physics engine
Since I prefer turn based games, I have no use for physics engine. Basic physic implementation is enough for my own projects. I haven't compared existing physics engine so I can't really answer your question there.
My own methodology to compare libraries is to:
a) check what are my needs
list all libraries that fufill my needs (checking if they have direct documentation for implementation)
c) look at the libraries interface to see which are the easiest to use.

That's all.

Ghostly yours,
Red.

I'm using Ogre3D and I quite like it. I've never tried Irrlicht so I can't really comment. Ogre3D can use a variety of API/frameworks (OpenGL/Directx etc) under the hood without you really needing to change much at all. It has lots of things going for it. I have a sort of fps game with it at the moment with menus/ui/animation/particles all working very well. I will say that the particle editor I use is fairly buggy, as is the ui editor. I pretty much end up having to write out xml/particle scripts without the editors they cause me so much trouble.

I use PhysX for my physics which was relatively simple to to get working with Ogre. I use blender for modelling (exporter works well). Over all I am quite pleased with Ogre, its just the ui/particle editors that are somewhat poor in my opinion.