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visplane overflow?

once apon a time this was the most hated doom error. It happened in many large open maps, mostly for me in pwads. This was finally goten rid of in new doom ports like Boom when ID released dooms sources. It was even in doom95 but was rare. I have little knowage of programing so i would like to know what this visplane overflow error ment. things i do know is it involved something with sectors in your visual range, i think in old school doom you could not have 10 or more sectors in your view. It also would give a number something like vispane overflow_666. For me and others who dont really know what it means i would like to know. I am glad this nasty bug is gone from doom

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I think it's more like 128 two sided lines in view at once. Beyond that, and you get the overflow.

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"Here's my best theory to-date about the real cause of visplane overflows:

Too many changing ssectors (sub-sectors) in view at once, with different floor and/or ceiling properties. Floors and ceilings count separately towards the limit, and only when each is actually visible to the player. Two flats are considered compatible if they have the same texture, the same lighting level, and the same height (unless the texture is F_SKY1, in which case height does not matter). If two visible flats are compatible, and they are only separated by a 2s linedef or by flats that are not visible, then the visible flats are merged into the same visplane."

-Lee Killough

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Fanatic doth sayeth:

I think it's more like 128 two sided lines in view at once. Beyond that, and you get the overflow.

I believe you are describing the edge overload HOM error, not the vistaplane error.

In earlier versions of DooM, you could not have more than 128 two sided lines in view at once, because DooM would only render a maximum of 128. After that, the DooM engine would ignore the additional lines, and the result would be HOM. This limit was raised in later versions of DooM.

I remember creating a cathedral for DeiM, that had edge overload HOM in DooM 1.1 as you entered it, but worked without trouble in DooM 1.9.

128 lines sounds like a lot, but apparently it includes all vertical surfaces too. If the view of a room is divided by a structure (i.e. a pillar), then the same lines will also count twice. Reaching the 128 2s line limit proved to be very easy in user made wads, which is presumably why id raised the limit.

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I had a visplane overflow error in a wad when I attempted to shape sectors to spell out "choose your fate." That's 14 sectors (letters) in one area. I guess I'll refrain myself from doing that again.

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You can get a visplane overflow with only two sectors.

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You can get a visplane overflow with only two sectors.


Then how come E1M1 of the Ultimate DOOM Never crashed with a visplane overflow after looking at the sectors in the Toxic slime room before the exit?

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Then how come E1M1 of the Ultimate DOOM Never crashed with a visplane overflow after looking at the sectors in the Toxic slime room before the exit?


Uh, because there are less than 128 visplanes visible in that area. Read my post above as to what a visplane is and see if you can't imagine a situation where two sectors could cause a visplane error...(hint, think giant chess board)

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