The Eternal Visplane Question

[The Ultimate DooMer]

What's the difference between 'no more visplanes' and 'visplane overflow'?

[Fredrik]

They are exactly the same thing, but called from different parts of the code.

[Bashe]

Holy crap!!!
I HATED visplane overflow! That was so annoying!
It happened right in the middle of the good stuff and then I forgot to save and it sucked.

Sorry about my pathetic attempt to bold a word...

[Ichor]

Use [b] and [/b] instead. Anyway, visplane overflows were the bane of all of my older maps. I can't remember the number of adjustments I had to make, sectors I had to rearrange, or entire rooms I had to delete in order to get rid of those visplane overflows or HOMs. Now, with the source ports, all that is a thing of the past, and I can finally let my imagination go wild, hahahaaa.

[Bashe]

What causes visplane errors? Too many walls or rooms or sectors and stuff?

[PumpkinSmasher]

they are caused by to many sectors in view at once. Fortunatly with source ports we don't have to worry about them anymore.

[Ichor]

It's more like too many different sectors (different flats, height changes, etc.) in view at once. If you had a hundred sectors in one room and the floors and ceilings were all the same height and the flats were the same, I don't think there would be a visplane overflow, but if they were all different, it's a sure bet that the game would crash.

[Bashe]

This may sound embarrassing, but I used to play Chex Quest when I was like, 6 (yes, I didn't realize it was pretty much Doom for kids).

The last room of the last level, whenever I went in there I would always get visplane overflow. It was really dumb.

[Volte]

http://www.rome.ro/lee_killough/editing/visplane.shtml

[Doom_Dude]

Bashe said:

This may sound embarrassing, but I used to play Chex Quest when I was like, 6 (yes, I didn't realize it was pretty much Doom for kids).

http://members.fortunecity.com/doomskin/chexquest/tucq.html

[The Ultimate DooMer]

I'm sure lines can cause it too - I tried improving a Plutonia II map by editing a grey building with metal strips down it. I brought the strips out by 32 units so they looked like the buildings in E4M3 of LTSD - but that caused a visplane crash in one place out there, whereas the original didn't. (and I made sure there were no extra segs, too)

[Cyb]

it doesn't have anything to do with sectors or lines or segs, it's do do with visible planes (as the name suggests). It's totally possible to get a VPO with only two sectors, and it's totally possible to have 512 sectors in view and not get a VPO (I believe the visplane limit is 128). I believe Lee's linked page explains it, but a visplane consists of a floor/ceiling with a different light level, texture or height than the immediate surrounding area.

This is actually dependant on what you see on the screen and doesn't have anything to do with visible sectors. For instance if you have one sector with three columns in the middle and you view the screen so all three pillars are in view in such a way that they 'split' the floor into multiple parts, that's now three visplanes (for the floor) even though there's only one sector.

On the flipside, you can also have two three sectors arranged as so (side view):

     1       2   ___________
__________      |
          |_____|     3

normally that'd be three visplanes, but if sectors a and 3 have the same flat and light level (but not the same height) if you view them from such an angle where both sector 2 and the lower sidedefs textures surrounding 2 are not visible (most likely from midway within sector 3), then 1 and 3 will be merged into a single visplane, even though there are three sectors.

and that is your doom engine rendering lesson for the day.

[Grimm]

Heh, didn't you ask this already, man?