Entities falling through the floor at a specific spot

[Kontingent]

I was finishing a WAD when I notices that monsters then the player could fall through the floor in the middle of a certain sector. There is no linedef in this spot. What causes this and how do I stop this from happening (as it is at a place where many monsters can converge on my map)?

I used gzdoom to run the map and Boom: Doom 2 configuration for editing on Ultimate doom builder.

Thank in advance.

 

Project1.zip

["JL" was too short]

I have only an anecdote to offer, rather than any definite technical explanation for you, but:

I had a similar issue in a map near an area with, to put it mildly, some highly complex and finicky geometry.  The problem seems to have been that I had some vertices that weren't lying exactly on the grid, which I'm thinking caused the editor and/or game to throw a rod somewhere in the process of building the underlying map structures (nodes and such). 

When I selected all the vertices in area and explicitly snapped them to the grid, the problem went away.  (I cranked the grid size down as finely as possible for this, which for a UDMF map in Ultimate Doom Builder is only 0.125 map units, so it essentially made no difference to the area's visuals—but it apparently restored enough sanity to the math that the game stopped misbehaving.)

Looking at your screenshot you've got some pretty elaborate/finicky geometry of your own going on, so maybe it's something similar?

[ViolentBeetle]

It's a result of nodebuilder issues, I think. But I'm not sure how it works. Usually caused by complex geomtry, like your cracks.

Dragging vertices near affected area around, even for a bit should cause nodebuilder to try again, possibly fixing this.

[Kontingent]

4 minutes ago, jerrysheppy said:

I have only an anecdote to offer, rather than any definite technical explanation for you, but:

I had a similar issue in a map near an area with, to put it mildly, some highly complex and finicky geometry.  The problem seems to have been that I had some vertices that weren't lying exactly on the grid, which I'm thinking caused the editor and/or game to throw a rod somewhere in the process of building the underlying map structures (nodes and such). 

When I selected all the vertices in area and explicitly snapped them to the grid, the problem went away.  (I cranked the grid size down as finely as possible for this, which for a UDMF map in Ultimate Doom Builder is only 0.125 map units, so it essentially made no difference to the area's visuals—but it apparently restored enough sanity to the math that the game stopped misbehaving.)

Looking at your screenshot you've got some pretty elaborate/finicky geometry of your own going on, so maybe it's something similar?

 

2 minutes ago, ViolentBeetle said:

It's a result of nodebuilder issues, I think. But I'm not sure how it works. Usually caused by complex geomtry, like your cracks.

Dragging vertices near affected area around, even for a bit should cause nodebuilder to try again, possibly fixing this.

 

Thanks, ill try to rearange the complicated parts in the map.

["JL" was too short]

To reiterate, I didn't bother manually adjusting anything, just mass-selected all the potentially offending vertices and used this option:



Assuming you've got the grid size cranked down as far as it will go, this will do a first shot at straightening everything out while making the smallest possible change to your existing designs.  Then you can (if necessary) perform any remaining adjustments by hand.

[Kontingent]

16 minutes ago, jerrysheppy said:

To reiterate, I didn't bother manually adjusting anything, just mass-selected all the potentially offending vertices and used this option:



Assuming you've got the grid size cranked down as far as it will go, this will do a first shot at straightening everything out while making the smallest possible change to your existing designs.  Then you can (if necessary) perform any remaining adjustments by hand.

I snapped the verticles to the second finest grid size and the issue disapeared. Thanks a lot!

[ramon.dexter]

This issue has nothing to do with grid snapping. Actually grid snapping is solely an editor feature, so having vertices snapped or unsnapped has zero difference. What causes to fix this bug is actually the simple rearrangement of sectors, when moving vertices around. This bug happens a lot on sectors, that has subsectors inside. Imagine a situation where there is a big sector with a smaller sector inside. The smaller sector is not connected by any linedef to bigger sectors linedefs. This arrangement can easily lead to invisible holes. Easy fix? Split the bigger sector into smaller sectors and the bug is gone.

[bofu]

4 hours ago, ramon.dexter said:

This issue has nothing to do with grid snapping. Actually grid snapping is solely an editor feature, so having vertices snapped or unsnapped has zero difference. What causes to fix this bug is actually the simple rearrangement of sectors, when moving vertices around. This bug happens a lot on sectors, that has subsectors inside. Imagine a situation where there is a big sector with a smaller sector inside. The smaller sector is not connected by any linedef to bigger sectors linedefs. This arrangement can easily lead to invisible holes. Easy fix? Split the bigger sector into smaller sectors and the bug is gone.

 

Kind of, but that's not the only cause. This sort of thing is much easier to trigger when your vertices aren't aligned on the grid because it tends to cause your linedefs to meet at weird angles that the engine doesn't know how to calculate, and if you're relying a lot on DoomBuilder to handle it when you're drawing overlapping shapes, it's going to make a few inevitable errors with regards to precision, and you can easily end up with some overlapping vertices that don't end up joining. Snapping things to the grid can cause these vertices to join because they get moved to the same spot, which triggers the merge behavior in DB.

 

Doom can easily handle subsectors inside larger sectors, as long as the math to calculate where everything is is nice and simple.

Edited April 10, 2023 by bofu

[esselfortium]

If your version of Doom Builder has the Node Viewer plugin, check that and see if there are any odd sharp subsectors jutting out into the affected area. If there are, there's your problem. The method to fix it is basically trial-and-error, jiggling some vertices around (especially ones that are placed on the 1- or 2-unit grid), rebuilding nodes, and checking the node viewer again to see if the problem has improved.

["JL" was too short]

11 hours ago, ramon.dexter said:

This issue has nothing to do with grid snapping. Actually grid snapping is solely an editor feature, so having vertices snapped or unsnapped has zero difference. What causes to fix this bug is actually the simple rearrangement of sectors, when moving vertices around. This bug happens a lot on sectors, that has subsectors inside. Imagine a situation where there is a big sector with a smaller sector inside. The smaller sector is not connected by any linedef to bigger sectors linedefs. This arrangement can easily lead to invisible holes. Easy fix? Split the bigger sector into smaller sectors and the bug is gone.

Not sure what you mean.  The grid itself surely has an existence in some sense, since the default alignment for flats is on, e.g., the 64 x 64 grid.  If by "editor feature" you mean that "snapping" is how the editor lets you make sure that your vertices are aligned with the grid at a certain resolution, well, yes, that's what I'm talking about.  Obviously once you save the map and run it in a Doom engine then no further "snapping" is taking place and the only question is where the vertices actually are and whether that causes the math to go screwy—as bofu mentioned. 

[IcarusOfDaggers]

On 4/10/2023 at 2:34 PM, esselfortium said:

If your version of Doom Builder has the Node Viewer plugin, check that and see if there are any odd sharp subsectors jutting out into the affected area. If there are, there's your problem. The method to fix it is basically trial-and-error, jiggling some vertices around (especially ones that are placed on the 1- or 2-unit grid), rebuilding nodes, and checking the node viewer again to see if the problem has improved.

 

Hijacking this thread. In my UDB, node viewer option is disabled for some reason. It used to be enabled