Damn fool question time!

Ok, What exactly is a HOM?

Tell me every thing there is to know about them.

Hall of Mirrors - A nasty graphic glitch that occurs from several causes.

Visiplane overflow
No texture in places where there should be textures
GL glitches
A sky flat for a floor and a ceiling in the same sector (E4M8 at the very end)
Using IDCLIP and walking outside the map.

They appear whenever the engine has nothing to draw, so it draws whatever was on the screen last.

It also appears if there are too many linedefs on the screen at once (vanilla only).

Heh, HOM is pretty much the only thing that no port has changed yet.

BBG said:

Heh, HOM is pretty much the only thing that no port has changed yet.

They've sorta changed it. In ZDoom, HOMs no longer "shimmer". Instead you get a sort of messy screen wipe.
IIRC, the reason HOMs would flicker in vanilla is because the engine drew the screen in colums, from left to right.

Quasar said:

DOOM, however, not being a true 3D renderer, draws everything to the screen as columns. If there are no source columns mapping to some area on the screen, then nothing is drawn there, and what you get is whatever was there before. Hence the blurring effect of HOM.

If you've ever noticed, in the original DOOM.EXE, HOM was a bit different because it shimmered, as opposed to being a static blur like it is in most ports now. This is an effect of mode x page flipping, and slight discrepancies between the screen and the back buffer. When the pages are flipped, the HOM shimmers slightly, giving it a sort of magical feel.

Assmaster said:

They've sorta changed it. In ZDoom, HOMs no longer "shimmer". Instead you get a sort of messy screen wipe.
IIRC, the reason HOMs would flicker in vanilla is because the engine drew the screen in colums, from left to right.

Legacy displays the sky in the void unless you look away from the map isself.