Why the axis plays hide-and-seek with me?

[jiangcaiyang]

I am learning Irrlicht and wants to build a scene and an axis. If possible, you can download the source files and help me troubleshoot the program.
Here is two problems about it:
1. I've make an axis as my custom node, however, when I rotate the camera, the axis is hidden bihind the mesh. It seems that it plays hide-and-seek with me.
2. Due to the visible edges, the skybox seems unreal, In irrEdit it is perfect. Is there any drawbacks in my code?

[hybrid]

The .irr format does not support proper texture settings upon load, which means that some artifacts can show up.
For render order, you probably have to render in two sections. First scene and then on-top models

[jiangcaiyang]

The .irr format does not support proper texture settings upon load, which means that some artifacts can show up.
For render order, you probably have to render in two sections. First scene and then on-top models

Could you help me troubleshoot the problem using my code?
I used to believe that everything ran well using my code, but result in some defects.

[hybrid]

IIRC, there is no solution yet for the skybox problem. You simply have to remove it and load it manually.