Textures changes in Cheogsh 2

[Barry]

http://www.doomworld.com/idgames/?id=15933
I just thought I should tell you this, that in the wad "Cheogsh 2", the textures on some pillars changes on level 5. It is the cages that go in
lava. You need to put on God mode, push a lever and the cage will lower (You need to go in the cage after you pressed the lever) into the
lava and you will see that the pillars textures of the cage will start making some sort of black pictures on it WHILE the cage is lowering itself,
but when the cage is standing still in the lava, the pillars look normal. I have the feeling I had seen this before, but I don't know where.
Here are the cages of the level where marines are being held. (One cage doesn't work, because the lever is broken): http://i49.tinypic.com/2vbq6ax.jpg
Here is a lever you should press to lower a cage: http://i50.tinypic.com/15wx95k.jpg
Here is what the pillars of the cage look like when you are lowered in the cage: http://i50.tinypic.com/2zpsj01.jpg
Here is what the cage's pillars look like when it is standing still: http://i46.tinypic.com/2w5klqv.jpg

[Barry]

So, could anyone understand what was going on here?
This is really nothing important, I know, it just caught my eye and I am wondering if there is something wrong with GZDoom, with the wad
or my computer (but I really don't think it has to do with my computer)

[Gez]

No idea, honestly. If you use a rather old version of GZDoom, I'd suspect it's the clamping bug; but that one was fixed quite a while ago already.

[Graf Zahl]

It's definitely not the clamping bug. I have done some tests some time ago but got no definitive results to fix it yet.

[Enjay]

Yeah, it looks more like z-fighting. It's like GZdoom is trying to draw 2 things in exactly the same place - I'm going to guess the surface of the texture and the edge of the red fog.

[Barry]

Did any of you play the wad and see it happen for yourself? Because, the screenshots doesn't show precisely what happens to the pillars.
(The black stripes moves as you move underwards)

[Alter]

Did any of you play the wad and see it happen for yourself? Because, the screenshots doesn't show precisely what happens to the pillars.
(The black stripes moves as you move underwards)

You should provide a savegame (and gzdoom version used) before that event, RIGHT BEFORE it. To make things easier for us.

[Graf Zahl]

I have seen the problem myself so I don't need a savegame. What I haven't seen yet is a reason for this glitch.

[Graf Zahl]

Finally - finally, this got fixed - but it took me an entire afternoon to debug until I understood what was happening...

The problem was that the 3D floor sorting did not account for all the cases that were caused by those cages lowering in the lava, leaving a partially sorted and partially broken list behind. Interestingly, the glitches were even worse in ZDoom's software renderer.