Hi DesuDeus,

> My bad, I mean how does MoI display two lines in two
> different styles (blue and red for example) when they are
> at the same place in space?
> Same for colored solids.

That's up to the video card to handle - items leave their z values behind when they are drawn and objects that are drawn after them only draw their pixels if they have closer z values than what is currently in the zbuffer.

It's not uncommon for 2 coincident surfaces to get slightly differing z values across their surface due to tiny round-off errors in numeric calculations, that causes something called "z-fighting" where different portions of each thing may show with a kind of patchy result.

- Michael