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NaturalTvventy

what's a visplane?

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So is a visplane any closed set of lines, or is it a sector? if I have a checkerboard made of two sectors separated into 129 squares, will that cause a visplane overflow the same way a checkerboard made of 129 individual sectors?

thx,

NT

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Yes, it will. Identical floors or ceilings, for the purpose of visplane calculation, can be split into as many or as few sectors as you like with no impact on the number of visplanes you're creating.

It's not as simple as just any enclosed shape equaling a visplane, though; how visplanes are generated for a frame depends on the angle and position the player is standing at in relation to the map geometry, whether there are structures such as solid pillars or raised/lowered sectors that split up a single floor or ceiling surface into two or more visplanes from the player's viewpoint, the complexity of the surfaces' shapes, and so on.

The way visplanes get split and merged depends on all these factors (and surely others I'm missing), and can vary significantly from one frame to the next depending on player movement and moving floors/ceilings. The more technical, specific explanations of what determines visplane splits and merges tend to go over my head.

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Incidentally, this 1997 page from Lee Killough mentions a situation similar to what you describe, with a checkerboard made from two sectors, beck when everybody was still guessing about visplane overflows.

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shesh, that page just keeps going and going....

follow up question, how do you know if an error is a visplane overflow in cdoom? My current level's crashing in cdoom when I try to run around it, but there's no sort of error screen upon exit of the level. I think it's safe to say as I know of no other error that would cause a crash in-game, but i want to be sure before I start trying to implement random walls to fix the problem.

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As far as I know, Chocolate Doom will usually print out either "R_FindPlane: no more visplanes" or "R_DrawPlanes: visplane overflow" upon a visplane crash, but not always.

You could always test in GhostlyDeath's Chocorenderlimits version though, as that has a handy visplane counter. I highly recommend it.

[edit: I believe that the blockmap limit and plats limit (and possibly others?) can also cause an in-game crash, but yeah, my money would be on visplanes here.]

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I know Chocolate Doom also crashes if you incur Medusa Effect, which sometimes occurs by using 2S (double-sided) lines as lines bordering the boundaries of a map.

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Megamur said:

Also, both Chocolate Doom and vanilla DOOM will get upset and crash if you use textures less than 64px wide as 2S middle textures.

They will? this is the first I've heard of it.

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esselfortium said:

They will? this is the first I've heard of it.


I never heard about it either, but try applying STEP1 - STEP6 or BLODRIP# as a 2S middle texture and watch the fireworks.

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esselfortium said:

At least some of those are multi-patch textures.


Is that what it is? Huh. Just a coincidence that they all happened to be less than 64px, whereas STEPLAD and STEPTOP worked fine and were wider than all the other STEP textures.

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Megamur said:

I know Chocolate Doom also crashes if you incur Medusa Effect, which sometimes occurs by using 2S (double-sided) lines as lines bordering the boundaries of a map. Also, both Chocolate Doom and vanilla DOOM will get upset and crash if you use textures less than 64px wide as 2S middle textures.


Double-sided linedefs as map boundaries seems like a pretty bad idea in general eh?

Well I checked all the fatal errors in the wiki and none of 'em seem to apply to my map. Does cdoom have errors that do no occur in vanilla doom? anyone know where I can get the vanilla exe so I can check if it occurs in vanilla as well?

Thx,

NT

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NaturalTvventy said:

Double-sided linedefs as map boundaries seems like a pretty bad idea in general eh?


Yes. Never, ever do that. :)

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If you have a CD version of Doom that uses Doom95, it might still have the DOS executables hidden on the disk. The one from the Collector's Edition doesn't, as far as I know, but my Ultimate Doom CD does.

In any case, I can take a look at the map if you want, to see if I can help find the problem.

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