I've created big collision floor, that is meant to be visible in editor and invisible in game. Now I have problem: I don't know, how to make it invisible.

I've followed Editormarker_box structure; place NiStringExtraData with MRK written in it into my mesh, but floor is visible in game. I cannot find anything else in Editormarker_box, that is responsible for invisibility.

I'll give what... Limited advice I can. I know that at least in Skyrim and Fallout that as far as I remember there is a null texture that can be put on objects and I think it's in there by default, it can be used to make things invisible. I don't know if that helps at all but maybe that provides a tiny clue at least.

I tested this out and it works for me - could you share your mesh file - maybe there is something else in it causing it to show up.

Here's my mesh: http://www.speedyshare.com/tGvV3/invFloorBig.nif