Invisible wall glitch

This thread is following on from some issues which are occurring for people playing the new wad Memorial by Eternal. This issue has happened to me in the past with wads of my own and is now resurfacing again on my current project. Seeing as no one in the Memorial thread could provide an answer other than "Use latest PrBoom-plus", I've decided to ask the question here in the Editing subsection.

The glitch involves hitscan shots not making contact with targets in certain maps(Memorial.wad's "map 5" section is heavily affected by the bug). It's as if the shots are ending up somewhere else in the map, because you don't even see the bullet puffs. Or like an invisible wall is eating your hitscan shots as soon as you fire them. The glitch doesn't affect projectile weapons like the rocket launcher though. I am running the latest ZDoom.

Any help would really be appreciated.

I've run into this one a few times. I think it may have something to do with the blockmap, though using another nodebuilder didn't help my problem in a few cases, and worked in others.

Long story short: All you can do as a mapper is to target a port that fixes these issues. This isn't something that can be solved by authoring your maps differently.

I think it's this bug; though it lacks a detailed write-up of the precise, mechanical causes by someone who understands why it happens.

DaniJ said:

Long story short: All you can do as a mapper is to target a port that fixes these issues. This isn't something that can be solved by authoring your maps differently.

While that may in fact be true, honestly it's a very unsatisfying answer. The link Gez posted seems to point to the culprit being "large sectors", meaning that technically you COULD solve the problem by authoring maps differently. Maybe by splitting large sectors up a bit? I dunno. What constitutes a "large sector" anyways? I have made maps with what I feel are very large sectors in them and this never happens, not after 150-200 playtest runs. But in a very few levels I've made it does happen, and often in small-medium size sectors, so that explanation might not hold water after all.

What's more interesting to me is that ZDoom doesn't fix the issue but PrBoom does. It'd be cool if Randy Heit included this bugfix in a later version of ZDoom.

EDIT: I found this, perhaps this is what Use3D was referring to?

I was trying to avoid delving into a deep technical explanation because that didn't seem to be what you wanted. Are you actually interested in the reason for the problem, or are you simply interested in what can be done to avoid it?

In my short answer, I was being a little economical with the truth because it is possible to construct your maps in a way that would minimize the problem. However, the rules for which are so esoteric and intrusive that doing so would severely limit the kind of geometry you can construct. Consequently, this "technically possible" point is entirely irrelevant outside of synthetic test cases.

Yes, that thread you linked to re entryways' and Maes' discussion is indeed (one of) the causes for this kind of issue in maps. However there are various others (many of which ZDoom already fixes, btw).

DaniJ said:

Are you actually interested in the reason for the problem, or are you simply interested in what can be done to avoid it?

Throughout human history, it's rare that problems have been solved without first having a clear understanding of their underlying causes. So yes, I'd like to know the friggin' reason for the problem, if nothing else so that someone more savvy than I might come along and solve the issue in the future.

There isn't one single reason for these issues. Maes has already adequately explained the cause of the issue seen in the thread you linked to. Many of the others are already explained on the DOOM Wiki. These issues are pretty well documented actually, now that I look at the wiki. We already know how to solve them, thats not an issue.

DaniJ said:

These issues are pretty well documented actually, now that I look at the wiki.

No.

The link you posted is two sentences which detail the symptoms with no explanation of cause. The link I posted is a discussion between people and basically amounts to speculation(one guy says he's "fairly certain" about a few things but none of it is conclusive). As Gez said, and I quote, "it lacks a detailed write-up of the precise, mechanical causes by someone who understands why it happens." So why am I to believe that you know how to solve the issue? Furthermore, if the solution is known, why isn't it being implemented?

Basically from where I stand, you either know the details and are too lazy to type them in a post, so you post a couple of sentences and waste my time, or you don't know shit and are blowing smoke up my ass.

Vordakk said:

No.

The link you posted is two sentences which detail the symptoms with no explanation of cause. The link I posted is a discussion between people and basically amounts to speculation(one guy says he's "fairly certain" about a few things but none of it is conclusive). As Gez said, and I quote, "it lacks a detailed write-up of the precise, mechanical causes by someone who understands why it happens." So why am I to believe that you know how to solve the issue? Furthermore, if the solution is known, why isn't it being implemented?

Basically from where I stand, you either know the details and are too lazy to type them in a post, so you post a couple of sentences and waste my time, or you don't know shit and are blowing smoke up my ass.

This kind of attitude won't get you much help.

Searcher said:

This kind of attitude won't get you much help.

You'd be frustrated too if someone kept posting in your thread telling you, "We know what the problem is, don't worry about it" instead of just spilling the fucking details. If you guys don't want to tell me, just say so and I'll stop posting and figure it out myself.

Just stop raging and use prboom+, the cause of the problem is a bug due to the fact that that map is absolutely gigantic.

DaniJ said:

Yes, that thread you linked to re entryways' and Maes' discussion is indeed (one of) the causes for this kind of issue in maps.

What thread? The only thing I saw him link here was a wiki discussion page where neither Maes nor Entryway posted anything.

Looks like zdoom does not include some BOOM fixes about this issue. For example, I have no any problems with "glboom-plus memorial.wad -complevel 9" on submap05, but with ZDoom I can't shoot line #2730.

Vordakk said:

You'd be frustrated too if someone kept posting in your thread telling you, "We know what the problem is, don't worry about it" instead of just spilling the fucking details. If you guys don't want to tell me, just say so and I'll stop posting and figure it out myself.

Making a gigantic sector can result in strange invisible walls that can block you even though they are not really there, and other strange things can happen. It is good to break up the sectors into many smaller sectors instead of one huge one. Due to the way the blockmap works. As mentioned in this thread linked below, if you make a HUGE map, it will have no-clipping on and monsters will be walking through walls with impunity. So keep each sector small, and not 10000 units on a side.

http://www.doomworld.com/vb/doom-editing/40113-my-big-map-has-a-big-problem-something-to-do-with-the-blockmap-i-think/

I was actually trying to help you Vordakk but given your attitude you can forget it. I won't waste my time writing this all up just for your benefit. Yeah, I'm so lazy that I can't be bothered to spend the next few days documenting every last underflow, overflow, precision, logic and numerical issue in DOOM's playsim just so that you can read that information and then ultimately do nothing with it.

Many of these issues are well documented at the wiki. Seriously, they are. Here is the thread I thought you linked to.

neubejiita said:

Making a gigantic sector can result in strange invisible walls that can block you even though they are not really there, and other strange things can happen. It is good to break up the sectors into many smaller sectors instead of one huge one. Due to the way the blockmap works.

Agreed. I occasionally used to have problems like invisible walls (which blocked everything, not just bullets or shotgun pellets) and "invisible" holes in the floor. I always found that creating a sector (however small or useless) within the problem sector would solve the problem.

I forget if it's possible to fix the problem by using a different node builder, but I vaguely remember that it is not.

neubejiita said:

Making a gigantic sector can result in strange invisible walls that can block you even though they are not really there

I believe you, but this sometimes happens to me on maps I make myself which don't have any gigantic sectors and which are not in any way large or complex maps as a whole. That's part of what I don't understand about the problem.

DaniJ said:

I was actually trying to help you Vordakk but given your attitude you can forget it. I won't waste my time writing this all up just for your benefit. Yeah, I'm so lazy that I can't be bothered to spend the next few days documenting every last underflow, overflow, precision, logic and numerical issue in DOOM's playsim just so that you can read that information and then ultimately do nothing with it.

You weren't trying to help me at all. You were making vague, meaningless, and utterly unhelpful posts while assuming I was much too stupid to understand the specifics. You said you wanted to "avoid delving into a deep technical explanation" because that "didn't seem to be what [I] wanted", but I never implied that I didn't want a detailed exposition. When I said that I would like a technical explanation you just kept dodging the question. And you admitted to "being a little economical with the truth", so it's tough to take you seriously at all. I'm fairly certain at this point that you really don't know what's behind this bug and just enjoy trolling the hell out of me. Well I guess you got me good, hope it was fun.

You haven't demonstrated that you would like this information for any other reason than because. After I pointed out that this has numerous causes, rather than reign in your demands upon me, you instead broaden their scope further.

You need to realize that providing you with the technical explanation you think you want would actually involve considerable work from someone here who has an intimate knowledge of DOOM's source code, ensuring the technical accuracy of that information, etc...

I am sorry you see my attempt at helping you as "vague, meaningless and unhelpful" but what do you expect given the broad scope of your question?

As for your assumptions regarding my opinion of you personally I really don't know what to say, I did not presuppose anything of the sort.

DaniJ said:

You need to realize that providing you with the technical explanation you think you want would actually involve considerable work from someone here who has an intimate knowledge of DOOM's source code, ensuring the technical accuracy of that information, etc...

Well I'm not exactly sure if Vordakk could do anything with such information, but I strongly recommend telling Randy Heit of these engine problems (if you haven't already, of course), so he can make a bugfixed version of ZDoom.

I suspect it's caused by overflow because of extremely long linedefs, I can't picture any other reason. The game must be at least detecting a linedef there, because hitscans cannot hit the floors and ceilings in Vanilla Doom (and even Heretic, where you can look up and down). What is the longest line in that area? Does splitting it in half do anything?

I guess the only other thing you can do is run it in a debugger to see where the code steers wrong.