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wesleyjohnson

BOOMEDIT wad has invisible lump not a sector

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In BOOMEDIT.WAD, in the room with the transparent glass in a square, there is a floating sign with sector numbers that do not match the sector.
What do other ports do with that rectangle on the floor under the sign.
It is not on the map as a sector and seems to be an artifact of the mismatched sidedef sector number.
I have seen it invisible using the software renderer. and as HOM (in opengl, on DoomLegacy and prboom).
But the player can step up on the thing.
I do not know if it is a feature that is going to show up in other PWAD, or a bug I should everything I can to kill.

Edit:
Translucent stained glass in a square, with sign that says
"260 Translucent".

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You mean sector 52. Note that lines 262, 263, 264 and 265 are tagged #60. Now check line 1882. You now see that all mid textures with tag number 60 will be translucent. Sector 52 has a brighness level of 255 so those mid textures also have this brightness. "Square" sector 52 ( floor and ceiling ) inherits the brighness level from sector 53.

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I will have to check all those line numbers on my work machine, but that sounds like the central pedestal, not the invisible lump.

There is a central pedestal in that room, and on it four sided transparent textured glass. That is not it.

The lump is between that pedestal and the door, under that floating sign.
There is something on the floor under that sign that makes the player walk on it as if it was a invisible lump in a Deep Water sector.
But it is not a sector, there is no sector in that room of that shape or position. It seems to be just around the floating sign that the engine is getting floor levels from "somewhere else".

DoomLegacy and prboom handle it in software renderer as an invisible floor. The opengl renderer in both display HOM there in the shape of a sharply defined and stable rectangle around the floating sign.

I was wondering if this is some recognized technique that is used in any PWAD, and thus needs to be preserved ??

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Well I'm nonplussed. Everything seems fine for me with prboom 2.5.0 in software renderer ???

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Could you upload on imgur some screenshot of the room in question?

I think you mean this thing by "transparent glass in a square" but I'm not entirely sure. Maybe you meant that instead?

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At first I thought he meant the first image, but I think he means the second, both of which I mentioned here. The first I edited and replaced with the second.

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First, it is entirely invisible, so screen shots are of no help.
You cannot see it, except if you run prboom or DoomLegacy in opengl mode (you see it as HOM). I don't know about other ports. The only other port I have available is Edge, have not got Gzdoom. I do not know how well Edge and Gzdoom preserve such weird effects, so I ask instead of performing random sampling of ports.


No, its not the glass floor platform, it is "that instead".

Edit: went to the other computer to get facts.
Wad is BOOMEDIT.WAD
Room is sector 54, platform is sector 53, stained glass is sector 52.
The floating sign is linedef 312, and says "260 Translucency".
The floating sign is in sector 53, but sidedef 1 and 2 are refs to sector 52, which is on the platform and is higher than the room floor. When the player walks under the floating sign, it is as if they stepped on sector 52.

It is hard to notice. Enter the room with the translucent stained glass (sector 54). Move really really slow forward, right before the platform (sector 53), under that floating sign (linedef 312). I step up on something before I reach the platform. It is not a sector and does not show on yadex (wad editor).

Try to walk around the central platform. On the left side (viewing from the door) you will step up and down on something invisible, that is not a sector. It must be the sidedef refs on linedef 312, that point to sector 52.

Some ports eliminate lines like the Floating sign, with both linedef sides in the same sector, at least for drawing. But this is player movement.

It has such sharply defined edges that it seems to be governed by some kind of engine rules.

Does any port detect lines with sidedefs that do not match the sector it is within ??

This probably would be caught by most every wad editor's checking.
I do not know whether to treat it as a engine bug, a feature, a wad bug, or an anomaly.
It would be nice to know if the effect has a name, then I could search for info on it.

It is not the only place in this wad. Also check the ceiling texture change on wall around the first room (right under the floating sign).
With opengl, the top of the wall disappears, and the player can jump into the hole in the wall (with a little work).

It seems to be deliberate as it appears on more than one floating sign.
Does anyone know what they were trying to accomplish ??
Is is an accepted method ??

Got to go, the lights have gone out and I am sitting in the dark, again.

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wesleyjohnson said:

The floating sign is in sector 53, but sidedef 1 and 2 are refs to sector 52, which is on the platform and is higher than the room floor. When the player walks under the floating sign, it is as if they stepped on sector 52.

That appears to be the cause. Linedef 312 is being handled as part of sector 52, consequently the player finds themself walking on air when passing under the sign. What I'd like to know is whether that particular engine trick/quirk was used deliberately or is just a happy accident.

Graf Zahl said:

What does GZDoom do?

Same as PrBoom+ - you walk on air.

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Yes, I "see" now. Risen3D behaves the same way, which is to be expected. No HOM though. I suspect it was an oversight by/of the author(s). What he/they should have done was assign both sidedefs of line 312 to sector 403 instead.

The current method can well be used for fences to block enemy movement ( not flyers ) and that the player can jump over, for ports that support jumping.

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Looks like it's a vanilla engine quirk, since this little test map ran in Chocolate Doom with just a couple of graphical glitches that I might have ironed out with a bit more work. The worst that can happen is walking into the invisible steps from the side and getting trapped between the linedefs.

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GreyGhost said:

Looks like it's a vanilla engine quirk, since this little test map ran in Chocolate Doom with just a couple of graphical glitches that I might have ironed out with a bit more work. The worst that can happen is walking into the invisible steps from the side and getting trapped between the linedefs.


didn't some wads use this effect in the 90s? I remmeber a game that you followed some invisible steps, by following candles all the way up.

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Csonicgo said:

didn't some wads use this effect in the 90s? I remmeber a game that you followed some invisible steps, by following candles all the way up.


That's probably Doomsday of UAC.

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Csonicgo said:

didn't some wads use this effect in the 90s? I remmeber a game that you followed some invisible steps, by following candles all the way up.

It's a similar trick, though in this case being done without self-referencing sectors. Can't think of any other maps that have used individual linedefs as steps (apart from possibly one of gggmork's), but that isn't to say there's none out there.

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wesleyjohnson said:

First, it is entirely invisible, so screen shots are of no help.

Oh ye of little faith.

First, it's not entirely invisible with everything:

wesleyjohnson said:

You cannot see it, except if you run prboom or DoomLegacy in opengl mode (you see it as HOM).

So you could post screenshots of the HOM.

Also, you can make a screenshot of the room when you are just in front of the invisible step, move forward a tiny bit to climb on it, and make another screenshot then, which will show that the player is higher than on the previous screenshot.

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It appears to be a violation of the doom wad sector definitions. Sectors are supposed to be complete.

1. It is too difficult to detect to make it worthwhile.
2. What would the engine do about it after detecting it.
3. It would be nice if OpenGL could display it correctly, but that seems to require detecting the mismatched sector reference.

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GZDoom doesn't glitch on this thing.

Does PrBoom really do? What about PrBoom+ then? It should be a lot more stable.


As for dealing with this thing it's actually very simple:

When assigning subsectors to sectors you need to do it a second time just for use by the renderer. And this time you have to ignore all two-sided lines with both sides in the same sector, getting the proper sector reference from neighboring subsectors.

This will only work, though, if you use GL nodes.

Or, if you use the GLU tesselator, discard all two-sided lines with both sides in the same sector when tesselating.

I don't think it's possible to handle this effect just using the regular nodes because they are missing necessary information to find a proper sector for rendering.


To make a long story short: It is essential to handle such things because there's countless maps using such stuff.

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