[Vanilla Level Editing] Lesson 9: Simple Moving Sectors

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The previous lesson introduced you to the concept of the remotely activated sector. The exploration of the range of actions that these sectors can be made to undergo continues in this room. In particular, you will extend your repertoire of effects that use moving ceilings and be introduced to those that involve moving floors.

The WAD Sorties from this room will have you adding some additional traps for the unsuspecting players of your growing WAD. There are also a few cautionary words against setting traps for yourself!

We begin, though, with one of the most useful moving floor effects: the lift.

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LIFTS AND MOVING PLATFORMS

In earlier rooms, you saw how DOOM produces the effect of a door by the simple expedient of moving a sector’s ceiling from the level of its floor to some other higher setting. Lifts are produced by an equally simple process. They are obtained by moving a sector’s floor from one level to another and back again. This creates a traveling platform that will carry whatever is standing on it along with it.

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HOW LIFTS OPERATE

DOOM’s lifts all operate on the same basic principle: When activated, the floor of the lift sector moves down from its starting elevation to the level of the lowest adjacent floor. There it pauses for five seconds before returning to its starting position. Appropriate sounds are produced as the lift starts to move and as it docks at each end of its travel.

Note that DOOM expects to start the motion of all lifts by moving them downwards. If a sector that has no lower floor adjacent to it is activated as a lift, it will not move. Furthermore, lift sectors always return to their starting elevation.

Lifts always move from the starting elevation to the lowest adjacent floor. They cannot be made to pause at the position of some intermediary floor. If you want to have a lift at the side of a tall room, say, operating between a high ledge and another ledge below it (but higher than the floor of the room), you will need to isolate the lift sector in some way from the main room to prevent it from continuing down past the intervening ledge to the floor of the room.

For a moving sector to function as a lift, players (and monsters) must be able to enter and leave the sector in both its upper and lower positions. Make sure that you allow appropriate headroom and maneuvering space in and around these sectors, if you want players and/or monsters to be able to use them.

If a lift’s floor is prevented from returning to its starting position because of the presence of a player or monster — either because there is insufficient headroom in the floor’s uppermost position or because the object overhangs the sides of the lift sector and thus contacts with an adjacent ceiling — then the movement of the lift will immediately reverse and the floor will return to its lower position. The lift will, however, persevere in its attempts to return to the starting position until it succeeds.Don’t forget you will have to allow for the full travel of the moving floor.

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TURBO LIFTS

DOOM v1.4 introduced a high-speed version of the lift, the turbo lift. Turbo lifts are the lift effect’s equivalent of the turbo doors. Apart from their higher speed, they operate in exactly the same way as standard lifts.

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DECIDING TRIGGER POSITIONS

Often the hardest part of building a lift is deciding upon a suitable triggering arrangement. You will recall that spacebar activators can only be operated from their right sides. This has major implications in the building of lifts, particularly if you want the lift to be capable of being operated from above and from below. The figure illustrates the problem.



The upper part of this figure shows a common arrangement, with a lift providing a link between two areas, the lower of which has its ceiling below the level of the upper area’s floor. In the figure, the lift is in its upper (resting) position. As you can see, both the upper and lower corridors end at the same line — the line marked A.

This line would be a natural place to have the spacebar activate the lift. This cannot be made to work from both above and below the lift, however, as this would require line A to be active from both sides. An alternative method must be found for triggering this lift. There are a number of possible solutions, all of which are commonly used.

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THE SIMPLEST SOLUTION

The simplest way of arranging triggers for a lift is to orient its lower sector boundary (line A) with its right side facing away from the lift sector, and set this line to be a spacebar activator of the sector’s movement. This enables a player to summon the lift from below, while standing against the sector edge. The lift is set to trigger from above by means of a walk-through trigger action placed on the lift sector’s upper boundary (line B). This causes the lift to descend as soon as a player steps into it from the adjacent upper area.

Case i shows the arrangement of trigger lines. A right-angle tick mark on a line shows a spacebar-activated line’s right side; oblique ticks mark walk-through trigger lines.

This configuration of triggers requires the player to think of activating the lift from below, while providing automatic triggering from above. It can be used to build lifts that may not be obvious at their lower level, and thus are missed, or lifts that surprise the player who enters them from above with sudden, unexpected activation. (Readers familiar with the start of MAP05 of DOOM II may recognize this!) These lifts can also deliver monsters automatically from the higher to the lower level.

In building a lift in this way, remember that the walk-through line providing the upper trigger will operate whichever way it is walked through. Players traveling up in this lift will therefore send the lift back down as they step from the lift at the top. You may regard this action as undesirable; or you may wish to use it so that the lift is sent back down to collect whatever is tracking the player along the lower level!

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FORCING MANUAL OPERATION FROM ABOVE AND BELOW

To implement a lift that the player must activate manually from above and below, an additional trigger line is needed. If this line is positioned 16 units or less from line A, the difference in floor heights that occurs at that line will prevent the player’s center point from crossing the additional line. (Players are 32 units wide, remember.) By orienting these two lines with their right sides facing away from each other, and placing the same special attribute on each, the lift’s lower boundary can be made to appear active from both sides. A player will be able to activate the lift from the “end” of either corridor. Case ii illustrates this configuration of triggers.

It does not matter on which side of line A the new line is placed, provided that it is no further from it than 16 units and that the two lines have their right sides facing away from each other. If the lines are placed farther apart than a player’s radius, it will be possible for the player to stand between the two lines and be on the left side of each — and thus not able to operate the lift!

A lift configured to use switches in this way cannot be activated by monsters.

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FULLY AUTOMATIC LIFTS

A fully automatic lift is produced by using walk-over triggers on both the line of the upper boundary of the lift sector (as before) and on the approach to the lift from below. This also requires an additional line, of course. Note that here the activator used on the lower approach must be positioned more than 16 units from line A to provide the player with the space to cross it when the lift is in its raised position.

Provided the triggers are of the standard (non-turbo) variety, such a lift could be activated by monsters from either side. For effective use by monsters from below, however, the lower activator will need careful placement. It must be placed far enough from the lift to enable a monster to cross the activator and provide the lift with sufficient time to descend. The distance should not be so great, however, that the monster cannot reach the lift before it goes back up. If a monster cannot step straight onto the lift sector’s floor when it gets to it, then it will turn and wander off in another direction. You may need to spend some time experimenting, using IDDT IDDT to watch the way monsters behave to get these lines just right.

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TRIPLE TRIGGER OPERATION

In the previous arrangement of active lines, players who step off the lift at the lower level will need to move forward to cross the lower activator if they wish to summon the lift back. As the lower activator will not normally be visible, few players will think to do this, especially if, having seen what is at the lower level, they decide they need to beat a hasty retreat! It is common, therefore, to arrange for the line-A boundary of the lift to provide an additional spacebar activator for summoning the lift from below. This triple-triggering is probably the most useful arrangement of lift triggers. It is shown as case iii.

Note that again it is vital that the lower walkthrough activator be positioned more than 16 units from line A. If it is any closer, neither of the triggers for summoning the lift from below will work. The walk-through trigger fails because there is no space for the player to walk through it; the spacebar trigger fails because DOOM will not enable the player to access it through the walkthrough trigger that lies between the player and the line of the lift.

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UTILIZING DIRECTION CHANGES

Lifts are generally good places to have a corridor change direction. This has two advantages. First, it can force the player to turn rapidly as the lift operates in order to face the hazard on the other level. Second, it can make the placement of triggers simpler.

The figure shows a plan view of two corridors at different levels running at 90° to each other. The corridors meet at a lift. Assuming the corridor from the south is the higher of the two, line U could be used by players approaching from the upper level to operate the lift using the spacebar. Line L can then be utilized as the spacebar activator for players in the lower corridor.

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COMPLETELY REMOTE OPERATION

There is no reason, of course, for a lift’s activating triggers to be positioned on or around the lift itself. They could be moved well away and placed on any standard trip or switch line. This can force players to hunt around for either the lift, the switch, or both. (They will usually need to make a run for it, too!)

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ONE-WAY LIFTS

Similarly, there is no requirement for lifts to be capable of operating from above and below if you don’t want them to. Remember that players can always jump from open-sided lifts.

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TEXTURE CONSIDERATIONS AROUND LIFTS

As with all surfaces that the user is expected to activate with the spacebar, it makes sense to use lift-like textures on the visible faces of lifts in order to alert the player to their presence. PLAT1 is the usual lift-face texture, although some of the door textures are suitable, as indeed are many of the standard wall textures.

More important than the textures themselves, though, is their application to the appropriate texture slots. Note that line A has essential textures on both sides: an upper when viewed from the lift sector itself, and a lower when viewed from the bottom corridor.



It is also easy to forget that moving floors expose additional surfaces. The figure shows how a lift sector gains a completely new lower texture (along line B) when it moves to its lower position. Few editors will check the range of a lift’s operation sufficiently to provide you with a warning of such hidden essential textures.

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PEGGING CONSIDERATIONS FOR LIFTS

Pegging considerations around lifts are much easier than around doors. You usually want all textures to use the default arrangement. Ceiling relationships don’t change with the operation of lifts, so the state of the upper unpegged flag is always immaterial. Lower textures are usually left in the pegged state so that any visible outer face of the lift moves up and down with its floor, while the inner faces of the lift (the walls of the lift shaft, as it were) remain pegged to the static floors outside the lift sector, and thus stay stationary themselves.

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STEPS INVOLVED IN BUILDING A LIFT

The steps involved in building a lift are as follows:

1. Make a suitable arrangement of sectors. The floor of the lift sector should be set at the upper limit of its travel.
   
2. Check that textures are applied to all lower texture slots that will be exposed by the movement of the lift.
   
3. Check that the lower unpegged flags of all lines bordering the lift are clear.
   
4. Decide on suitable trigger lines. The disposition of these will depend upon the precise arrangement of the lift and adjacent sectors. Assign the appropriate special attributes to the trigger lines, and tag all of these lines to the lift sector. Make sure that any spacebar-activated lines have their right sides facing the direction from which the player will approach them.
   

The next WAD Sortie takes you through this process in your own WAD.

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WAD SORTIE 18: LIFTS AND MOVING PLATFORMS

The first step in adding a lift to your WAD is to construct the upper and lower areas that the lift is to connect. The lower level will be an entirely new area of your WAD, to the north of the platform room, while the upper area will be an extension of the corridor that leads out of the platform room.

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PREPARING THE NEW AREAS

Below shows how the new areas fit into the existing map.

Begin by drawing a large open arena connected to the existing thin courtyard sector beyond the platform room’s northern window. Make sure you draw this new area in a clockwise manner — don’t worry about its exact size and shape — and connect it correctly to the existing sector. Lower its floor to –256 before continuing.

Next, draw the first of the sectors that lead out of the large sector’s southwest edge, using GSTONE1 as the wall texture. Set this new sector’s ceiling to –128 and its floor and ceiling textures to DEM1_5 before drawing and making the subsequent sectors of this new lower area of the map. It doesn’t really matter how many lines or sectors you use to come around the corner — just aim to meet up with the existing corridor behind the impact-activated door, noting from the figure how this is to be extended.

The full development of this lower area will be left to later Sorties.



To draw the new area above the lift, and add new sectors as shown below, using PIPE2 as the wall texture, working from the room beyond the impact-activated door. In order, these new areas will be the following:

• A second impact-activated door
  
• A short corridor beyond
  
• A third impact-activated door
  
• A further short corridor
  
• The lift
  

When fully drawn, the two new areas of the map should be left with a gap of about 24 units between them.

The following table gives the sector settings for the new areas above the lift. The lower areas can be left as they are, for now.





Finally, bridge the connection between the new areas of the map by adding the two missing lines and making the new sector. Set this sector’s ceiling at –128 and its floor at –256.

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MAKING THE LIFT

This lift is to be spacebar-operated from above — its presence is not going to be too obvious — but automatic from below. To make the lift, set the special attribute of the western line of the lift sector to 62 (SR Lift Lower Wait Raise), making sure that this line’s right side faces east, into the upper corridor. Tag the line to the lift sector. This will enable the player to activate the lift with the spacebar from the upper level.

To make the lift come automatically to a player approaching from the lower area to its west, set the special attribute of the line at the western edge of the thin interconnecting sector to 88 (WR: Lift Lower Wait Raise) and tag this line to the lift sector too. Make sure that this line is more than 16 units from the lift; otherwise the player will not be able to cross it to activate it from the west when the lift is up.

Now deal with the textures for the lift. Use BROWN1 for the side walls, with BROWNPIP on the end wall of the upper corridor. Remember that this wall is formed from the upper texture of the lift sector’s western bounding line. (If you put BROWNPIP on the main texture of this line, you can expect the Medusa effect when you activate the lift.) Set this texture’s upper unpegged flag for better texture alignment (remember that this flag can be used with impunity around lifts) and give it a Y-offset of 72. This is to give a small visual clue to the presence of something below the floor. Put PIPE4 on the western face of the lift where it blocks the lower corridor (the lower texture on the other side of the same line as above, of course).

Next, apply textures to the essentials on the eastern edge of the lift. Use STEPTOP on the eastern lower essential. This essential is brought about by the fact that the lift’s floor is set higher than its neighbor’s to the east. As the lift’s ceiling is lower, this line also has an upper essential. Use PIPE2 on that. Don’t forget that the lower texture slot on the western side of this line will become an essential as the lift descends, so you will need to put texture there too — I’ll leave the choice to you. This completes the construction of the lift.

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FINISHING THE CORRIDOR TO THE LIFT

Before trying out your new addition, finish the approach to it by setting appropriate triggers and tags for the two new impact-activated doors. Use the PIPE4 texture on their uppers with some different X- and Y-offsets applied to move the bullet holes around a bit. You should also set the appropriate Secret on map flags for these doors. You can leave the PIPE2 texture on the through-door side walls.

Try a modification of the hazardous area of this corridor just outside the original impact-activated door, too, by putting the BLOOD1 texture on the corner sector’s floor, as some warning of the harmful effect of standing in this sector. Next, add some explanation of the presence of blood here by splitting this sector’s eastern wall so that it has a small section somewhere in it of 32 pixels length. Put BLODRIP1 on this small section of wall. This texture has a blood-splashed lower edge and will need its neighbors to be set to the matching PIPE1 if it is not to look odd.

This change creates a further problem, though. You now have a single blood-splashed wall that even in the lower lighting conditions of this sector will look a little odd if surrounded by clean walls. Some adjacent textures need to be changed to match. These currently carry a hint to the player on how to proceed further, though, through the presence of their bullet holes. It would be nice to be able to preserve this hint.

The wall that is really the impact-activated door presents no problem—it uses both upper and lower textures. Its lower texture can be changed to PIPE1, with a Y-offset of –16 to move the pattern’s lower edge down to the floor of the blood pool. PIPE4 can be left on the upper, as these two textures will meet with a correct match. The lower texture between the corner sector and the corridor to the south can be changed in a similar manner.

That just leaves the northern wall. There is a problem here because DOOM does not provide a texture that has both a blood-splashed lower edge and bullet holes. It seems as though our visual clue may have to be sacrificed. Rather than do this, though, why not treat this wall in the same way as the western edge of the pool? If you turned the northern wall into a door, you could use its upper and lower textures to hold the two different patterns needed to satisfy the various visual requirements.

To do this, draw a new sector to the north of the corner as shown. Only a single sector is needed: it will act as both door and room. For now, just make the room — don’t bother implementing the door trigger, that will be taken care of later.



The new sector’s floor and ceiling heights should be set at –96 (32 units above the floor of the blood pool). Set the lighting level to 96, and use FLOOR4_1 as the floor and ceiling texture. The walls can be whatever you fancy. Use PIPE1 on the essential lower texture beneath the face of the new door, applying a Y-offset to compensate for the raised floor of the new door-room. Put PIPE4 back on this line’s upper. Don’t forget to remove the damaging special characteristic that the new sector will have inherited from its neighbor.

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ANOTHER LIFT

Finally, before trying out the WAD, add another lift to make it easier to get back from the large open arena at the end of the new passageways. Mark off a small portion of the arena where it adjoins the thin sector to its south, as shown.



The new sector should be given the same settings as the area adjoining it to the south. Then flip one of its northern lines around so that its right side faces into the arena sector to the north. Give this line a special attribute of 62 (SR Lift Lower Wait Raise) and tag it to the new small lift sector. Deal with all of its essentials.

Before saving as D2WAD18.WAD and trying it out, you might also like to make it a little easier to test this WAD by moving the Player 1 Start position nearer to the area of interest. You should find that you can do a circular trip out from the platform room, through all of your new sectors, and finally arrive back through the platform room’s northern window. You may find you have some essential textures to fix along the way but everything should work fine.

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OTHER MOVERS

Apart from doors and lifts, DOOM provides a number of additional triggers for the activation of simple floor and ceiling movements. These actions come into the general category of movers.

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SIMPLE MOVERS

All movers operate between their current level and some target level. Most are designed to act in one direction only, either up or down, in an on-off movement. The motion itself will be accompanied by a grating sound that continues until the movement is completed. Players (or monsters) trapped by these movers in gaps too small for them will stall the movement while they remain in the sector. The sound of the action will continue, however, and the movement will go on to completion as soon as the cause of the obstruction leaves the sector.

The moving sector itself will not prevent players or monsters caught in it from moving, although its motion relative to adjacent sectors may, of course, make it impossible for them to leave. Trapping players in this way is not a good design feature: it requires the game to be aborted — never a popular move.

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ABSOLUTE MOVERS

Absolute movers will only move in one direction to the finishing height. Note that those that move up by a constant amount do so per activation and will move even if doing so takes the sector’s floor above its own ceiling. It is probably wise to prevent this from happening, by limiting in some way the number of times that players can access the trigger.

The actions that move a floor to its next higher adjacent sector will act cumulatively. The floor will move up to successively higher levels on each activation until there are no more higher neighboring floors.

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USE OF SHORTEST LOWER TEXTURE

The actions that raise floors by the amount of the shortest lower texture determine how far to move by inspecting the textures used on the sidedefs facing out from the active sector. DOOM looks at the height of the patterns in use on the lower texture slots of all of these sidedefs and moves the sector by the height of the smallest short texture it finds there. If there are no textures of less than 128-pixel height in use on these lower slots, then the sector moves 72 pixels instead, for arcane reasons. (If you really must have a sector raise by shortest lower texture to the tune of 128 units, someone on the forums can give you the nitty gritty.)

Note that the distance to move is determined from the height of the texture itself, not the space it is occupying, and is therefore independent of relative sector elevations. This action is designed to provide steps that rise out of the floor. The short lower texture usually provides the pattern for a riser. Bear in mind that raising the sector to a height where more than one vertical tiling of the short texture is required to render the space it occupies will cause the Pink Bug effect. A short texture could, however, be used on a face that will never be visible to act as a control of how far the sector will rise on each activation. Once again, this action can drive the floor above a sector’s own ceiling if allowed to repeat too many times.

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RELATIVE MOVERS

Relative movers take their target positions from adjacent sectors. These may be above or below the sector’s current floor level. DOOM has specific expectations of the direction in which each particular action will move the floor. If the target position lies in the direction opposite to that which is expected, the movement will still occur, but it will be instantaneous and (virtually) silent. As you might imagine, the ability to make a sector change heights instantaneously can be put to great effect...

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MOVING CEILINGS

In comparison to moving floors, there are surprisingly few actions that create simple moving ceilings. Table 9.4 gives the list of what is available. These actions differ from doors in their speed (they are much slower) and their accompanying sound, which is the standard grating noise associated with movers.

The first of these actions (40) behaves as a relative mover. If the highest adjacent ceiling is below the target sector’s ceiling, then the ceiling will come down instantly.

Again, as with simple floor movers, the presence of players or monsters in the active sector can prevent the action from completing until the sector is vacated. This does no harm to player or monsters.

The next lesson, “Complex Moving Sectors,” examines moving ceilings and floors that do harm anything caught between them. Before that though, the next WAD Sortie leads you through the addition of some simple movers to your WAD.

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WAD SORTIE 19: SOME SIMPLE MOVERS

In this Sortie, you will develop the area beyond the lift and add some simple movers. Before that though, there are a couple of movers to add to the platform room.

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A WAY INTO THE SOUTHERN COURTYARD

So far, whenever you have wanted to examine additions to the southern courtyard, you have had to lower the floor of the window sector in the editor before playing the WAD. Let us create a switch to do this during play. This switch will be positioned in the secret room that was made a couple of Sorties ago off the southwest stairway, just outside the platform room.

The modifications needed to implement this change are straightforward. Start by putting a SW1BROWN texture on one wall of the secret room. (I suggest putting it somewhere on a short wall in one of the shadowy wings, where it may go unnoticed.) Take whatever steps are necessary to center a single instance of the switch texture horizontally on your chosen wall. Set the special at- tribute of the line carrying the switch texture to 102 (S1 Floor Lower to Highest Floor) and tag the line to the platform room’s southern window sector.

Note that the secret room’s height is somewhat small for this switch texture to look good here; the switch will be very low if the default alignment is used. Changing that alignment will spoil the match of the BROWN1 component of this texture, though, and will draw more attention to it. The best solution here is to reduce the floor level of this wing of the room — take it down to –32. Put a suitable texture on the essential lower texture that this produces and the changes in the secret room are complete.

Don’t forget to check that the tagged window sector’s floor is set at 56 units — otherwise this switch will have no work to do! You ought really to check that the lower texture of the wall under the window is pegged so that it appears to open correctly. However, because the player is unlikely to make it back in time to see this action occur, and because the lower texture is unpegged to provide better texture alignment, I suggest you leave it as it is.

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MODIFYING THE NORTHERN WINDOW

Let us also modify the platform room’s northern window, by making it start closed and arranging for the player to trigger the opening of it. It would be nice to have the ceiling rise from the window sector’s floor position, but the only actions that achieve this are door actions — which would be inappropriate — and a ceiling mover that ends at the height of the highest adjacent ceiling.

This latter could be used, but it would be fiddly to implement. Because this mover takes the ceiling to the highest adjacent sector, using it would require the closed window sector to be isolated from both the outdoor sector and the room sector. This would necessitate the splitting of the existing window sector into three long, thin areas: a new window sector down the middle, with the remains of the original window sector on each side of it, cutting it off from the sectors with high ceilings and providing the desired target ceiling height. Furthermore the presence of the window would be suggested by the remaining recess visible from inside the room, and while this could be disguised with the use of suitable textures, it would still be less than satisfactory.

A simpler solution is to use a moving floor, starting at the current window sector’s ceiling level. This solution will still require the splitting of the existing window sector to provide the final floor height, but it will only need to be split into two sectors, not three.

Using a fairly high Zoom factor, divide the current opening into the platform room down its long center line to turn it into two long thin sectors, as shown in Figure 9.8. Use Make Sector on the southern of the two new sectors first. Set its lighting level and ceiling and floor textures to match the original sector’s. Set its floor and ceiling levels to match the outer window sector’s ceiling height.



Put STONE3 on the appropriate lower texture of the new line. You may need some offsets applying to the through-wall textures to keep the bricks looking right here.

Finally, choose a line to act as a trigger to open the window. (I suggest the line of the second step up to the platform, so that the window opens as the player climbs the steps.) Tag the chosen line to the new sector, using a special attribute of 19 (W1 Floor Lower to Highest Floor).

You may like to try out these modifications before continuing with the development beyond the lift.

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DEVELOPING THE LOWER AREA OF THE WAD

The figure shows how the corridor area beyond the lift can be developed. You may like to try implementing this area, working from the description that follows.



The area beyond the lift (the lift is indicated by the mouse cursor in the figure) has been broken up into a number of sectors to provide variations in floor and ceiling height, a puzzle (or two), and alcoves for switches.

Working around from the lift, the new areas are as follows:

• Lift trigger sector
  
• Long southern corridor (with switch alcoves)
  
• Southwest corner section
  
• A sunken section of corridor (with another switch alcove)
  
• A raised section of corridor
  
• Northwest corner section (ceiling trap)
  
• Long northern corridor
  
• A small step (with switch alcoves)
  
• Short northeastern corridor section
  
• Door recess
  
• Door
  

The location of these areas is marked in the figure. There is also another door recess between the door and the large outer arena, but that will be left as it is for now and will not be discussed further in this Sortie.

Before implementing any of these areas, it might be helpful for you to know something about the functions that they will perform.