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netnomad312

Dummy Sectors

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I guess using dummy sectors is one of the more advanced editing tricks for the vanilla doom engine, but I dunno. Personally, I had never seen the point in them until about two days ago...

The situation: I was, and still am, designing a garden/greenhouse level (map18 for Tower of WAR). I had this idea to create a sector, out in the garden, that falls and becomes a nukeage pit. Then you would go through the earthen tunnel that this runaway radiation had burned for itself, up to the point where it started, inside the building (apparantly one of WAR's treatment machines had a weak wall and it spilled out).

The dilemma: a huge patch of dirt with no trees or flowers on it would be slightly obvious. I had to find a way to make the trees sink into the nukeage, even after the rest of the pit had stopped falling. So I made my first dummy sector.

Later on, I made a bridge across the pit, with a switch to raise it. This required another dummy sector, as this bridge sector was not connected to the tunnel like the sector as a whole was. Actually I didn't need to make a whole new, tiny dummy sector like I had for the sinking trees; I just made another "part" of the tunnel sector and connected it to another "part" of the bridge sector.

Like I said... I didn't know what they were good for until now. Is there anything else dummy sectors are used for?

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Yeah I use them alot, for lifts and doors that I want to behave in a certain way. And vanilla bridges do use them too, for the part you're actually standing on.

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Then you would go through the earthen tunnel that this runaway radiation had burned for itself, up to the point where it started, inside the building (apparantly one of WAR's treatment machines had a weak wall and it spilled out).


Heh, clearly inspired by Enigmatic Complex. :P Uh, I dunno if this counts as dummy sectors, but to eliminate sound pipes you put all your monsters in an area that is the same sector as the one you want the player's sound to "wake up" da monsters. Another way to use dummy sectors is to make 'em and then give single sidedefs that sector. You can some interesting things with this, and I think some cool lighting tricks can be pulled off with it. Of course, you'll end up with open sectors, but Vanilla Doom can actually handle it . . . at least with BSP 5.0.

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Dummy sectors are generally used outside the rest of the map as points of reference for other sectors. A few uses are:

Lighting - Suppose you have a room with a dais at the far end, and on that is an important item resting on a square slab of stone. Now, you want to have the entire dais use strobing lights, but the sector inside has nothing to reference to, so the sector blinks from 0 to 255 while the dais blinks from 120 to 255. Put a dummy sector outside the map and split it in half. Then take all the sidedefs of one sector and reference them to the stone slab sector inside. Then give the other sector the same light value as the one next to the dais. This also works with the slow pulsating light effect

Stairs - Stairs don't always have to go up. In Memento Mori map 1 and in my Crypts map, the stairs build downward. First build the floor with the stair sectors like normal. Then for each step, make a dummy sector (splitting it in two and referencing one the linedefs of one of the sectors to that step) and make the floor the value you want that step to stop lowering. Then give all the stair sectors the same tag number and use Floor_LowerToLowest. Now, you may be thinking that they will all just lower to the lowest step, but no. As each step lowers, it reaches the lowest floor at that time, and then stops. The step in front of it will lower past that step to the next lowest floor, and so on until all the steps have lowered. Loads of fun and it has plenty of uses.

Single Line Sectors - This is for rising gates, solid fences that act impassable for ground monsters and players, but not flying things. I don't have time to explain this one right now. Maybe a little later. It really adds to the atmosphere when used properly, but the downside is that GL ports don't like this and they generally want to scramble the effect.

Invisible Floors, Stairs and Bridges - This requires a different kind of dummy sector: one inside the sector your referencing. Make a sector, then make another sector completely inside the first sector. Flip the linedefs of the inner sector, then make the back sides reference the inner sector, thus making the inner sector self-referencing. Next, take the linedefs of the inner sector and move them as close to the sides of the outer sector as possible (4 or 8 units is good). Now you can change the floor to any height you wish, and still not need textures for the side. The classic uac_dead.wad has a perfect example of this. However, GL ports don't like this either, and they want to put a flat on the top of the invisible platform, and leave the bottom with a massive HOM.

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Uh, that sounds neat but I didn't really understand any of it. Perhaps you could churn up an example WAD in your spare time?

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Another use for a dummy sector is as follows:

In vanilla DooM you want to trigger some explosions, but you don't want barrels visible. You can do that by having a hidden sector with barrels in them and a linedef that triggers a crushing ceiling over the barrels in the hidden sector. If you must have a fast crushing ceiling you do not have the option of a silent crusher. This could pose a problem, as the player hears a crushing ceiling somewhere in a hidden area. The solution is to first create a dummy sector with a crushing ceiling, and place them away from where the player might hear them. Then create the hidden sector and crushing ceiling, and use the same sector references as the dummy ones. Then, after the explosions have been triggered there won't be the (unexplainable) sound of the crushing ceiling.

(Of course, if you can do with a slow crusher then you don't need to worry about this. In a map I recently did, however, I needed a fast crusher.)

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Well, not to self-promote but I use a lot of dummy sectors. Here's a great example:

ftp://3darchives.in-span.net/pub/idgames/levels/doom2/Ports/g-i/grind2.zip

In Grind2, I used plenty of dummy sectors. Download it and see. First off, head to the right. Through the door there's one enemy and a computer. The box behind opens like a door, but doesn't open fully. I used a dummy sector to do that, since doors only open to the lowest adjacent ceiling. I do this a lot because I often find doors to look a lot nicer if they don't "open" all the way (4 units below lowest adjacent ceiling).

Next, if you head across, down and up the stairs, through the doors and into the room with the pipes and fake slopes, you can turn and go into a room with a floorswitch with an arrow on it. To make both lower the same distance I used a dummy sector. Since they're both marked with "lower floor to lowest adjacent" the middle part, the arrow, wouldn't have moved, but with the dummy sector it does.

Now go outside. Make sure you've been to the room with the Arch-Vile and opened up the little part. You see the box of dynamite? Well if you go into the room and hit the switch it does two things:

1) Entering the room hits a tag that says "Raise floor to lowest adjacent ceiling"
2) Starts a crusher that crushes some barrels and makes a boom sound.

The floors that raise will actually end up lowering though, and you'll see why. They're attached to some dummy sectors that have very low ceilings; even lower than the floor started off at. This makes the Doom engine instantly drop it to that height. Instant drops can be very useful. You can also do the reverse and do an instant raise if you do it right.

Also, there's not one in the map (I don't think) but using "Raise floor to lowest adjacent ceiling" can be VERY useful. I made a map once that had an entire area tagged off and connected to dummy sectors. Using this you could make an entire room raise slowly, like an elevator, regardless of any boxes, crates, or architecture.

Onto another map of mine that has some useful dummy sectors: ftp://3darchives.in-span.net/pub/idgames/levels/doom2/Ports/d-f/dream.zip

If you head into the caves there's a lift with a box and a sheet of metal on it. If you hit the lift, you'll notice it all moves and stays at the same height! Look off to the side in an editor, dummy sectors do this. A lift always lowers to the lowest adjacent floor, so connecting them to other sectors is the key.

If you run across the map and find the nukage pool room (by the yellow key) you'll find another good dummy sector. When you hit the switch on the other side the floor seems to instantly be missing nukage. In fact, it doesn't hurt anymore either. A few dummy sectors help this by raising the floor by only 1 unit with "Raise floor to match next higher, flat, and type"

Well I hope this post helps you out some. =)

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Following up on what ReX said: basically, if you place a dummy sector far enough away from a switch that does something to it, you won't hear the relevant action sound (door opening/closing, floor or lift raising/lowering) even if you're standing right next to or even in the 'real' copy of the sector.

This very useful for 3D bridges (so that you don't hear a 'clonk' sound when you pass over or under them) and the aforementioned fast crushers, but there are other possible uses for it too, e.g. you can lower or raise a wall behind the player without them hearing it ;).

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NiGHTMARE said:

....but there are other possible uses for it too, e.g. you can lower or raise a wall behind the player without them hearing it ;).

Heh, wicked!

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Ichor said:

Lighting - Suppose you have a room with a dais at the far end, and on that is an important item resting on a square slab of stone. Now, you want to have the entire dais use strobing lights, but the sector inside has nothing to reference to, so the sector blinks from 0 to 255 while the dais blinks from 120 to 255. Put a dummy sector outside the map and split it in half. Then take all the sidedefs of one sector and reference them to the stone slab sector inside. Then give the other sector the same light value as the one next to the dais. This also works with the slow pulsating light effect

Hmm... guess that makes sense. But I really don't understand, did you once make a wad with this effect? Where is it?

Ichor said:

Stairs - Stairs don't always have to go up. In Memento Mori map 1 and in my Crypts map, the stairs build downward. First build the floor with the stair sectors like normal. Then for each step, make a dummy sector (splitting it in two and referencing one the linedefs of one of the sectors to that step) and make the floor the value you want that step to stop lowering. Then give all the stair sectors the same tag number and use Floor_LowerToLowest. Now, you may be thinking that they will all just lower to the lowest step, but no. As each step lowers, it reaches the lowest floor at that time, and then stops. The step in front of it will lower past that step to the next lowest floor, and so on until all the steps have lowered. Loads of fun and it has plenty of uses.

Wouldn't making just one linedef refrence the stair sector cause open sector errors?

Ichor said:

Single Line Sectors - This is for rising gates, solid fences that act impassable for ground monsters and players, but not flying things. I don't have time to explain this one right now. Maybe a little later. It really adds to the atmosphere when used properly, but the downside is that GL ports don't like this and they generally want to scramble the effect.

I have rising gates... but halfway up you see an under-floor HOM. So most of the time I deliberately put the trigger pads away from the gates (but not far enough away not to hear them rise).

As for GL ports... they don't like the way my nodes were built (and no, I'm not going to use another node builder) and give out HOMs sometimes. I've stopped caring about GL ports long ago.

Ichor said:

Invisible Floors, Stairs and Bridges - This requires a different kind of dummy sector: one inside the sector your referencing. Make a sector, then make another sector completely inside the first sector. Flip the linedefs of the inner sector, then make the back sides reference the inner sector, thus making the inner sector self-referencing. Next, take the linedefs of the inner sector and move them as close to the sides of the outer sector as possible (4 or 8 units is good). Now you can change the floor to any height you wish, and still not need textures for the side. The classic uac_dead.wad has a perfect example of this. However, GL ports don't like this either, and they want to put a flat on the top of the invisible platform, and leave the bottom with a massive HOM.

You mean the inner sector refrences itself on both the front AND back sidedefs? That would mean more errors...

Again, I don't give two craps about GL ports at this point.

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netnomad312 said:

Wouldn't making just one linedef refrence the stair sector cause open sector errors?


Not if the sector in the void is closed properly. (which it will be - the linedef is just an extra)

netnomad312 said:

I have rising gates... but halfway up you see an under-floor HOM. So most of the time I deliberately put the trigger pads away from the gates (but not far enough away not to hear them rise).


That's a natural effect - it's like briefly seeing a sector with lowered ceiling but no upper textures. It's nothing to worry about. If you're really bothered about it, you could make the doors turbo. (so you won't really see the hom before the door hits the roof)

netnomad312 said:

You mean the inner sector refrences itself on both the front AND back sidedefs? That would mean more errors...


Again, no errors because both sectors are properly closed to begin with. (the only trouble is you won't be able to highlight the sector without making the outward facing linedefs refer to the sector it's in. But you can change them back to self-referencing afterwards)

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Ok, I just made a small map with some of the dummy sector effects. Here it is.

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Are dummy sectors used to make "void space" where ypu have a window which can be seen through and has a glass texture of some kind on it, but monsters on the other side dont react to the player and you cant shoot thbrough it, or is that something else?, i wish i knew how to do that, but when ive looked at it in map editors in people's finished levels it just looks like a huge collection of linedefs of varying types XD, maybe somewhere there's step-by-step's abput these various invisible platform ect techniques

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You can, but the easiest way to do that is to put in a sector with floor 1 unit below the ceiling, as that will be invisible and nothing will see you. Of course if you want the window/bars etc. to lower (raising can be done an easier way) then you'll need to use dummy sectors.

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Making invisible platforms is easy.

A) Make a room (sector 1)

B) Make another sector inside this with a higher floor height (sector 2)

C) Make sure the linedefs you created in B) are all 2-sided

D) Make it so that the linedefs created in B) reference sector 2 on both sidedefs.

Bingo, you're done :)

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OK. This thread is a convenient place for me to ask this question that has been nagging me for the longest time. What the heck is a dummy sector?!!!?!?!? I know they're important, but why? Everytime I see something that involves dummy sectors, I give up because I am so confused about them.

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I just made a simple map which has a few examples of what dummy sectors can do. Of course, ACS scripting makes dummy sectors just almost obsolete.

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insertwackynamehere said:

What the heck is a dummy sector?!!!?!?!?


A sector with 2 separate groups of linedefs - one group (1-sided) out in void space (and is also connected to another sector out there), the other group (2-sided) in the playing area of the map.

Both groups reference the same sector, and the trick is to make the sector do something - the 1-sided group of linedefs moves normally (that's what the other sector in void space is for) and the 2-sided group of linedefs does something weird. (eg. raise instantly)

Ichor said:

I just made a simple map which has a few examples of what dummy sectors can do. Of course, ACS scripting makes dummy sectors just almost obsolete.


Nearly, although they're still useful for lighting effects.

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With scripting you can make all sorts of nice lighting effects that even dummy sectors can't do. They are useful for rising gates and solid realistic fences.

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The solid realistic fences in your wad were pretty cool! Also how you didn't get a HOM when you made the gate rise...

UD: I would love to make them turbo... except they aren't doors. They're W1: Up to highest ceiling. I'm sure there's a way to make them doors, and actually I think I know what... but how Ichor did the rising gate is what I was trying to accomplish (with no homs).

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the only time I ever use dummy sectors in my maps any more are for transfer heights and with elevators that have more than one sector. they aren't even necessary for things like instant move sectors or transparent doors (the latter can be done with transfer heights). Oh, I also use a 64x64 sector to teleport the player into during cutscenes or somesuch, but I could really stick him in some remote area of the map if I wanted, I'm just weird like that

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Do not use door rising commands on those rising gates (S1_DoorOpen, etc.). The gate will change to an HOM the moment you hit that switch (and I'm not sure the door will even open). It must be a ceiling rising command.

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Yeah... that's what happened. Now I remember. I tried it once a while back. But it didn't work, so I went back to using the W1 ceiling thing. This means I need "trigger pads" to make it work. These pads are 8 units above the floor and have FLOOR1_1 for their floors... at least, it was that way until the other day when I recolored that flat and added FLOOR1_2, 3, and 4. Now I have red, green, and gray versions of that flat (and similar colored below textures), so when you run over a colored pad, you'll know what color laser bar you've opened.

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but there are other possible uses for it too, e.g. you can lower or raise a wall behind the player without them hearing it ;).

Dude. Woah.

I have rising gates... but halfway up you see an under-floor HOM. So most of the time I deliberately put the trigger pads away from the gates (but not far enough away not to hear them rise).


The Doomworld Editing Pages might be able to help you with this.

As for GL ports... they don't like the way my nodes were built (and no, I'm not going to use another node builder) and give out HOMs sometimes. I've stopped caring about GL ports long ago.

Try GLBSP. I agree, though, I see no reason to worry about GL ports. It's not like ports actually cost money to get or anything. You can always just download a Direct3D port.

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Exactly. In fact I'm going to be sure to reccomend ZDoom 2.0.47 in the text file when it's done. Older versions of ZDoom showed HOMs in my wad's sky, as well... but 2.0.47 builds the nodes itself first. Also, I'm told by some of my playtesters (members of my DC clan mostly) that in some ports (I believe JDoom was one), it wouldn't even show my rising gate... it showed "a gray wall." *shrug*

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Er... I tried a lighting effect using dummy sectors, but it doesn't work right. The goal: three sectors, one inside the other, and originally 120 in light effect, would brighten to 140, 160, and 200 respectively when you walk into the room.

Originally, I made the center sector (212), then the surrounding sectors (213, 214). Then I created dummy sectors for each one (215-217). Upon walking over the line, though, all three brightened to 200. I didn't understand at first, but I guessed that it started by looking at sector 212, setting it to 200, and then looking at 213, and setting it to 212's light level (instead of its corresponding dummy sector which was 160).

I guessed that if I did the effect backwards it would work. So I deleted all sectors 212-214 (and thus the dummy sectors now have those numbers), and built the sectors starting with the farthest out. This time I thought it would work, but instead all the sectors went to 140.

Am I missing something, or is this not possible?

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Is this what you wanted to do? I think I see what the problem is. It all had to do with the dummy sectors all having the same tag number. The way I got around that is to have not one, but three trigger lines set very close together (in this map here, it's 1 unit apart) with the same command, one for each sector. Then I gave each of those sectors a different tag number, and...presto!

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The dummy sectors weren't tagged at all, but the sectors connected to them were. I've been trying to avoid doing multiple tag things like that, but I guess I don't have a choice... *shrug*

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