[http://sourceforge.net/p/ufoai/bugs/2321 Item 2321] imported from sourceforge.net tracker on 2013-01-28 19:30:37

When we rotate the 3D geoscape, models magically became invisible when we move it on the back of the glob.

We can use alpha value, when the model is a little on the back of the glob, and a fully transparent when the model is more on the back, but we should really not have a hard visible/invisible state.

Maybe it is very hard to do. It need to fully rework the geoscape rendering. But i dont know.
===== Comments Ported from Sourceforge =====

====== tlh2000 (2010-01-25 06:55:45) ======

problem is in MAP_3DMapToScreen imo - we should ask kracken about this. he's our math genius :)
====== kracken (2010-01-25 07:33:24) ======

This problem is linked to:
https://sourceforge.net/tracker/?func=detail&aid=1898022&group_id=157793&atid=805242

3D geoscape display was one of the first thing I made for UFO:AI. Now that I understand better how 3D display works, I'm quite sure I didn't code the proper way: openGL functions should be used to rotate models. This way, models would go behind earth and become invisible only when hidden behind earth.
I started working on that last year (or maybe even more?), but I had a problem with the flipped axis used in quake.
I opened a tracker at that time to write my conclusion, but I don't manage to find it anymore (silly me...). The problem was that due to this flipped axis, the model did not become invisible when going behind earth, but when it was in front of it! I'm almost sure there is a way to fix that, as battlescape use a flipped axis and the depth view is good. But I don't know what this way is...
This is however IMO the only proper way to recode 3D model drawing. If you use alpha value as you suggest, you would see the half transparent model over the earth. I tried this kind of trick, and you just get the feeling that the model made a U-turn and came back above earth.
====== kracken (2010-01-25 08:08:40) ======

The tracker I mentioned is:
http://sourceforge.net/tracker/index.php?func=detail&aid=2460883&group_id=157793&atid=805242


====== bayo-fr (2010-01-25 18:00:37) ======

I think there is no problem to display models using the depth buffer, but in this case i think there is thing to display before and thing to display after (model, text, layer over the map). I is what i mean when i said "rework".
====== kracken (2010-02-06 14:04:03) ======

This is fixed in trunk, r28454