I am currently investigating several free/open source OpenGL based 3D engines, and was wondering if you guys could provide some feedback on these engines and how they are to work with in a real world project.
The engines being compared are (in no particular order):
Crystal Space
Panda3D
Irrlicht
These are the main ones i know that are cross-platform, any there any others that i should be looking at?
You may also want to look at Ogre 3D: http://www.ogre3d.org/
Unfortunately I don't have any experience developing with Ogre or any of those you mentioned.
If you just want a graphics engine I recommend Ogre3d. It is very powerful in that regard. If you want the beginnings of a game engine - i.e. something that is easy to plug networking, game entities, physics, etc into, then I recommend Crystalspace 3d. I've used cs3d (Crystalspace 3d) for making games and it was easy to get it up and running quickly - but Ogre3d seems to have more to offer in how you can tweak your graphics, but it isn't as easy to hook in all the other game stuff as a package like Crystalspace.
Btw, there are tons of comparisons of these engines if you just google it.
You can find a lot of informations on lot of engines on this database.
CrystalSpace is a full engine so it's a monolithic bloc that you have to customize for your needs. Irrlicht too but it's made do do things easy. The counter effect is that it's hard to do specific things.
Now, i think Ogre might be the most general purpose hardware accelerated 3D rendering engine around here. Maybe Horde3D is better suited for specific high quality rendering but nothing that cannot be done with Ogre too.
More focused on large terrains than games (think GIS or flight simulators) there is also openscenegraph
Terathon makes an engine called C4. It is a game engine with a very mature set of features that is impressive for a $350 engine that includes full source code. The engine is available and being used on the PS3 as well, so this is a very solid platform. Not sure if you're considering just 3D graphics engines, or full game engines, but thought I'd mention it.