Irrlicht Engine

Hi, my problem is about mesh converting, I want to ask some questions.
1. does different format has different coordinate system?
2. if the answer is yes, then is coordinate system important? I mean, can I ignore this difference in my converter?
3. I converted out a bone animation, but the result is different from original. To solve it , what should I do first?

most common problem is to have 1 axis inverted so that left will be switchted with right or up with down. You have to mirror you mesh inside your 3D editor (I mean mirror, don' try negative scaling that will invert also normals resulting in wrong lightin).

so, I meet this problem, please have a look.
http://irrlicht.sourceforge.net/forum/v ... 28#p269328