Good day.
Currently I'am looking for 3D engine for iOS written on C++ as powerful as Marmalade and I don't know which to choose.
Why C++? I need it to be crossplatform (for future plans). Why not Marmalade? If I'll use Marmalade it means that I can't anymore use my favorite Objective-C libraries and frameworks. I want to make interface/network/all using XCode and just one screen will contain 3D scene (and I need to do many things here. Shaders, CSG, texture masking, boolean operations, procedural mesh generation, etc).
Unity is a pretty popular 3d engine for iOS. Check it out: http://unity3d.com
You may also check out Cocos 3d which is an extension of Cocos 2d which is written in C++. http://brenwill.com/cocos3d/
You can also check out http://irrlicht.sourceforge.net
You may also find some information on these posts: https://gamedev.stackexchange.com/questions/21/easy-to-use-cross-platform-3d-engines-for-c-game-development