LESSON 6: PUTTING SECTORS TO WORK

By now, you should be familiar with the role of the sector in DOOM WADs and be comfortable with its use and structure. In this lesson, you will be shown how sectors are put together to form the common types of elements that make up the traditional DOOM world. The various Sorties from this lesson will lead you through the addition of several new areas to the WAD that has been developed in earlier lessons.

Remember, though, that WAD-building is more of an art than a science — there are no fixed ways of producing anything. Consequently, you will not be given rigid rules or instructions for the implementation of every scenery element you will ever want. This lesson is intended as a gallery of ideas. Use it as a starting point for planning your own maps.

AREA DESIGN

Part of the secret of successful WAD-building is learning to plan and construct your sectors. GZDB is usually good about divining your intent from what you draw, but it's not perfect; moreover, if you begin an area and then begin to heavily modify and redraw it, it's possible for errors to creep in. In general, it's better to have a clear idea of what you are going for before you begin drawing lines, or at the least, you should have an idea of when it might be more fruitful to delete an area and start over, rather than extensively reworking what you already have.

PLANNING THE MAP

In planning your WADs, you should remember that no matter how beautiful (or ugly, if that’s what you prefer) you make your WAD, it is unlikely to be much admired unless it plays well. Keep this thought uppermost in your mind at all stages of design.

In particular, you should question your motives for the introduction of every new area. Ask yourself “Why am I creating this area? What will it contribute to the game?” Keep a mental tally of how many times you reply “For decoration” or “To add atmosphere.” Ornamentation is undoubtedly a significant aspect of any design, but if it becomes more important to you than creating a functional space to hide weapons or to ambush opponents, you are probably spending too much time using your editor and not enough time playing what you produce there!

Once you’ve answered the fundamental question of what your new map area is really for, you can turn to the more practical questions of how it should look, from the specifics of textures to the overall design scheme. How high will it be, how wide, how long? Will it be brightly lit or should it be dark? How high above other areas should it be? Will it have overlooks? Should it be hidden? Will it contain any tricks or traps?

In considering your approach to these design questions, you should be fully aware of all the features of the DOOM world that are available for exploitation. You also need to know about DOOM’s inherent design restrictions.

APPEARANCE

The look and feel of your map will develop as you go along. You’ve seen some of this already. You know a little bit about textures and lighting levels, and you will see some more specific and atmospheric examples of these capabilities as this episode progresses. These aspects of your map’s appearance can be used for more than simply adding atmosphere, however. DOOM’s lighting levels can vary from very bright (a setting of 255) to pitch black (a setting of 0). Obviously, dimly lit areas can be used to make the players’ task harder; it is easier for you to hide things in the dark — be they goodies, switches, traps, monsters, or the pathway itself. Try to use lighting levels realistically — take a close look at the way lighting levels are utilized throughout id Software’s E1M1 for an excellent example of this. Also, try to vary the lighting levels through your WAD so that players don’t get too accustomed to (or bored with) playing at a particular light level. Areas of darkness can be much harder to play when they follow immediately after well-lit areas.

Exercise careful thought in your use of textures, too. Aim for more than mere decoration. Beside lending atmosphere to your WAD, textures can create challenges of their own — some enemies are harder to spot against some surface colorings, for instance. Textures are also invaluable in providing clues to various aspects of your design, clues about such things as hazards, traps, and secret locations. Observant players will soon pick up on your textural pointers and will enjoy the game all the more. Of course, you can always throw the occasional false pointer into the mix to trip them up every now and then!

There are no hard-and-fast rules about the basic appearance of your map areas. If you’ve played many WADs, you will already know what particular design aspects you like. If you can’t decide, perhaps you should play some more and give it additional thought.

LARGE AREAS OR SMALL?

The sizes of the various areas of your map will be influenced by the functions you see these areas fulfilling. Do you intend to give the player a large open space in which to charge around and battle many foes simultaneously? Will you force the player to take on a few monsters at a time by confining the action to a smaller space? Do you want to restrict the player’s options for movement or escape?

Is this one of those twisty mazes that do their best to disorient and confuse the player? Will this area be built to contain a particularly unusual menace?

The effectiveness of many of the weapons in DOOM is related to the geography in which they are used. The geography also affects the way monsters behave, particularly in their tracking of the player. You should test out these aspects of your design fairly early in the design process, especially before you have too many lines and sectors to rearrange if you find that things are not working well.

To create map areas that function correctly, you will need to know something of the way DOOM’s objects and its geography interact. You need to know what can fit where in the DOOM world. You also need to be aware of the movement constraints that DOOM applies to both players and enemies.

SIZE CONSIDERATIONS

If you want areas of your map to contain particular objects, you will need to make sure that the areas are large enough to hold whatever you place there. You need to know something, therefore, of how things are measured and the restrictions on where they fit.

THING METRICS

You will remember from Lesson 2, “Reconnaissance Debriefing,” that all Things have both a width and a height. These two values determine an object’s “footprint” — how much map area it needs and what headroom it requires.

The term “width” as it is applied to Things is a little misleading, since it implies that Things are circular, whereas, in fact, they are square. This square is always oriented with the map’s coordinate system, irrespective of the direction in which the Thing faces. This needs to be taken into account when calculating where Things will fit, particularly for those Things that can move around, such as players and monsters.

THING COLLISION DETECTION

A Thing is deemed to be in contact with anything that touches or overlaps the square it occupies. The consequences of these contacts depend upon the type of Thing involved. Players who touch upon bonuses will obtain them; monsters reaching walls will change direction; players or monsters colliding with Things that are classed as obstacles will find their progress barred.

Things that move around (players and monsters) can only enter gaps that are wider than their diameter (allowing for the fact that it is really a square) and at least as tall as they are.

Note that for the purposes of inter-object collision detection, DOOM regards all Things of the obstacle category as being of infinite height. Players can never leap over a barrel, for example, no matter how far below them it is.



The fact that Things’ extents are square and do not rotate complicates the WAD designer’s job. You have to bear in mind that players and monsters are wider when moving at angles other than one of the cardinal directions. Thus, wider gaps will be needed between obstacles if the player is to pass between them at angles other than due north, south, east or west, as the above figure shows.

In this figure, the smaller circles represent players, who are moving in the directions shown by the arrows. The larger circles represent obstructions (such as barrels). Notice how the real (square) extents of these items interact very differently from the way their visible (circular) shapes would suggest. The player moving due south between the obstacles can pass freely through a gap that would seem to be much narrower than the one which the other player is about to find impassable.

OVERLAPPING THINGS—STUCK MONSTERS

Most editors will enable Things to be placed anywhere on the map, even if they are actually too large for the chosen spot. Any object larger than the space in which it is placed, however, will look unsightly. The entire object will be rendered on screen by the engine, even though it is visually too large for the space it is in. As you can imagine, this usually looks odd.

If your objects are purely decorative, such as pillars, lamps, firesticks, and so forth, then it is largely up to you how tight a fit you want to make them. Objects growing out of walls, ceilings, or floors are likely to be viewed as errors, but that should be the only consequence of carelessly placed decorations and bonuses. On the other hand, the consequences of placing player and monster start positions in tight spaces can be much more serious.

If you place monsters or players in spaces where they do not fit, you will find that they stick tight and are unable to participate in the game. Stuck monsters will not attack a player, but they can be injured and killed, either by a player or by other monsters if they get caught in a crossfire. This effect has been used intentionally in some WADs — usually to ‘glue’ several powerful monsters together. None of these monsters can attack the player, who will set about disposing of them and then suddenly discover, with the demise of the last of its colleagues, the final monster becomes free to attack — usually just as the player runs out of ammunition!

Stuck players are there for good — or until they think to use the no-clipping cheat code! This is not an effect that many players will view as worthwhile.

REACHING GOODIES

If you are placing bonus items around your map, you will normally need to make it possible for the player to get at them. You will therefore need to ensure that the player can either enter the area (eventually!) to collect the booty, or can reach in to grab it. Players are 56 units high and have a diameter of 32 units, so they can only enter areas that are at least 56 units high by 33 units wide. As you’ve seen, this width restriction may be imposed by walls, or by impassable Things.

It is possible for players to reach the distance of their radius (16 units on the coordinate system axis) into areas they cannot wholly enter, provided that the area’s floor is not above their head — in other words, it must be less than 56 units above the floor on which they are standing.

RESTRICTIONS ON A PLAYER’S VERTICAL MOVEMENT

From playing DOOM, you will know that there is a restriction on the height that a player can step up from one sector to the next. This height restriction is 24 units — any greater and the engine will refuse to let the player continue onward. There is no limit on the downward distance that a player may fall without taking damage.

In the previous section, you were told that a sector must be 56 units high if a player is to enter. Whenever the player tries to step from one sector to another, DOOM checks that there is a gap of this size between the higher floor and lower ceiling of the two sectors. Therefore, if you are building stepped sector sequences, bear in mind that the player will be unable to pass down the steps if any floor-to-ceiling space between adjacent sectors is less than 56 units high.

MONSTER MOVEMENTS

Sector sizes are also important for determining monster behavior. Whenever they are awake, monsters will always tend to track players. Even when the player is not in their line of sight, awakened monsters remain aware of the direction of players and will generally head towards them, unless they are distracted — usually by being struck with weapons’ fire from other monsters who can see the player — or are constrained in some way.

Like players, free-roaming monsters cannot enter spaces that are smaller than they are. They also demonstrate a reluctance to enter spaces that will be a tight fit for them; the smaller the gap, the more reluctant a monster will be to enter it. For completely unimpeded movement, a monster will need a sector to be at least twice as wide as the monster’s own diameter.

Monsters can climb stairs just as a player can — all monsters with legs can step up 24 units but no higher. They are more careful than players about coming down, however (a topic that will be explored in more detail shortly).

MONSTERS’ REACH

Again, like players, clawed monsters (such as Imps) can reach into sectors they cannot enter — not to collect goodies, of course, but to savage players! For a player to be safe from such a savaging, monsters must be constrained far enough away for their (square) extent not to touch the player’s.

SIZING FOR BETTER TEXTURE ALIGNMENT

You have already seen the final sizing consideration: fixing sector sizes to ensure better texture alignment. In addition to the alignment problems you have experienced for yourself, some textures will look strange when replicated up or along walls. Often you will need to limit your sectors to certain absolute sizes (as well as grid locations) in order to use particular textures effectively or to minimize problems with their alignment.

Usually, however, the choice of textures, and the adjustment of the map to make them work properly, will be completely subordinate to the size and shape that the area needs to be to play well. If you have areas that already work well but you find that you cannot get the textures to look right with any of the available alignment mechanisms, it is usually best to look for another texture to use rather than to compromise your WAD’s playability for the sake of its appearance.

DIVIDING ROOMS INTO SECTORS

Once you’ve answered the fundamental questions of what an area is for and how it needs to be arranged, you can start to think about how it may need to be divided into its component sectors. You already know a lot about this.

WHEN DO YOU NEED ANOTHER SECTOR?

Way back in Lesson 2, you learned about the fundamental role of the sector in the WAD, and you learned to distinguish the WADster’s sector from the DOOMster’s “room.” By now you should be comfortable with the use of sectors and know when you should need to create a new one. It is worth summarizing here, however, the occasions when an area of the map will need to be in a sector of its own:

• When it needs to have a different ceiling height from its neighbors
  
• When it needs to have a different ceiling texture from its neighbors
  
• When it needs to have a different floor height from its neighbors
  
• When it needs to have a different floor texture from its neighbors
  
• When it needs to have a different lighting level from its neighbors
  
• Any combination of these
  

These are the reasons you are already familiar with. There is another:

• When it needs to be able to do something special
  

The next room deals with these special activities of sectors. The current room is confined to considerations of the kinds of scenery components (such as alcoves, staircases, and so on) that will require only simple floor, ceiling, or lighting changes for their implementation.

Note that all of the areas covered in the rest of this room are no more than perceptual elements of a map. Within the WAD, they are implemented either as individual sectors or as particular arrangements of sectors, but there is nothing particularly special about them.

SIMPLE SECTORS

Many areas of the map require (or at least benefit from) additional sectors within or adjacent to them, acting as both decorative and structural features. These sectors are frequently very simple in form. They generally fall into a number of fairly loose categories.

PILLARS AND COLUMNS

Pillars and columns provide useful cover for players in otherwise open rooms. They can be added either by leaving void areas marked out within the room sectors (as you saw in our first WAD sortie), or by means of their own sectors, with suitably elevated floors. Which method is adopted depends largely on the appearance you want the pillars to have: if the pillar is to reach from floor to ceiling (as most do), the easier and more economical method in terms of space is to use the void.

ALCOVES, LEDGES, AND PLATFORMS

Alcoves are small areas generally set into the walls of larger rooms or passageways. Ledges are longer, thinner areas, usually running along the walls of rooms: they are frequently at a considerable height from the main room floor, and, if the player is to enter them, they will need to have some mechanism or provision for access. Platforms are usually raised areas within rooms.

All of these areas are common components of DOOM WADs and provide good spots for scattering bonuses, power-ups, and, of course, enemies. Trying to locate the access points to these locations (or even just spotting the locations themselves) can be a major element in playing rooms that contain them. As well as providing good ambush points, alcoves are suitable locations for secret switches and such like — which you will learn more about shortly.

You should already know enough about sectors to see how all of these areas can be implemented. Each is likely to need nothing more than an appropriate sector, set as necessary into or alongside a larger sector. You will see the building process in the next WAD Sortie.

POOLS, PONDS, AND PITS

Pools are areas containing liquids through which a player may pass, with or without harm. Ponds are usually deeper, and their higher sides may trap the player, forcing a hunt for an exit — usually in the form of a single step or a lower side somewhere. Pits are deep areas from which players can expect to have major difficulties extracting themselves. Pits may need to have some special sort of escape provided if you don’t want the player to be trapped in them forever.

Again, these types of areas should already be familiar to you. They are used as traps for the unwary, areas that wreak havoc if the player falls into them, or simply as obstacles that need to be skirted.

The techniques for building these areas should already be obvious to you. They are simply sectors with appropriately lowered floors. Pools and ponds will generally have animated textures on these floors. Often, these areas will cause harm to players who spend time in them. (You will see how to implement these harmful effects in the next lesson.)

STEPS

Steps are a common feature of DOOM WADs. You have one in your own WAD already. Additional sectors functioning as steps are needed to enable the player (and/or monsters) to move freely between sectors with a difference of floor height greater than 24 units. They provide changes in the vertical levels of your WAD, preventing the player from always having to fight on the flat, which thus makes for a more interesting game. You have already seen that they can affect monsters’ behavior, too. Steps are also a convenient means of making floor texture changes look better.

WAD SORTIE 9: ADDING ALCOVES, PLATFORMS, AND POOLS

Having described a number of basic map elements, I think it would be useful for you to add a few of them to your WAD. By doing this, you will get a better feel for the way sectors can work together and become more conversant with GZDB’s methodology for adding sectors to your map.

ADDING ALCOVES

The areas that are to be added in this Sortie are relatively straightforward. Start GZDB with D2WAD8.WAD and begin with a simple alcove or two, as described in the following text.

At this stage, the alcoves you are adding may appear purely decorative in function. I have plans for them later, however, so don’t let that worry you after all I’ve said about decorations!

ENTRANCE DOOR

The first addition is something which, in my opinion, no WAD should be without: an explanation of how the player got to the start position. I always feel that a player’s materialization at some arbitrary point in the middle of a room detracts immediately from the realism of the situation. Therefore, this WAD will have an entrance door. The door will be firmly locked with no hope of escape through it, but at least the player will have some point of reference from the start of the WAD.

All that is needed for this entrance is a simple alcove of an appropriate size to hold the right textures.

Preview these textures and note the following information: DOOR3 is 64 pixels wide and 72 pixels high. This texture needs to fill the alcove’s back wall completely; its size therefore dictates the width and height of the alcove. LITE3 is 32 pixels wide; this provides the depth of the alcove. FLAT18 looks to be composed of two tiles, each 64 pixels wide by 32 deep. Either half of this flat will therefore fit conveniently on the floor and ceiling of the planned alcove, but you will need to ensure that the alcove is drawn squarely in either the northern or southern half of one of the map’s grid squares.



The new alcove is to be added towards the western end of the south wall of the main hexagonal room. Start by adjusting the line that marks the southern wall so that it lies along one of the east-west grid lines (or precisely halfway between two, if that is easier). Then add the new lines for the alcove in a clockwise sequence, with each running along conveniently located grid lines. Remember that you want the new sector covering exactly one half of one of the grid squares; this will automatically make it 32 units deep and 64 units wide.

Set the new sector’s floor height to 8 and its ceiling at 80. (It needs to be 72 units high, remember).

The lighting level of the new sector can be left at 144. Apply the appropriate textures to the alcove’s surfaces. There are a couple of essential textures that will need to be dealt with where the alcove meets the main room. STONE2 would seem appropriate for these. Unpeg the upper and lower textures here to ensure that the textures align correctly with the adjacent walls. Finally, put the player start positions close enough nearby to suggest that this is the door through which they’ve arrived.

PASSAGEWAY ALCOVES

The next additions to the WAD will be a pair of alcoves in the southeastern passageway. I’d like these to face each other in the section of the passage that runs SE-NW, just out of the hexagonal room. One of these alcoves is to have the SW1GARG texture on its back wall, the other is to have SW1LION. Both of these textures are 64 pixels wide, so each alcove needs to be this width. Their depth is not crucial — a value of 24 units or so will be fine.

You should be able to add the appropriate new lines and create these two new sectors without any further instructions from me. Getting the lines the right length here may prove tricky — just do your best. Reducing the Grid setting to 4 or so may make the job a little easier.



I would like each alcove to be 72 units high; once you’ve made the new sectors, bring the ceiling height down appropriately. The rest of the sector settings can be left the same as those of the passageway. Use STONE2 for the side walls of the alcoves to match the passageway. You will need a Y-offset of –16 to keep the mortar lines continuous here. The upper essential should be STONE2 also, and, as you know by now, will need to be unpegged. Finally, apply the SW1GARG and SW1LION textures as required to the back walls of the alcoves. If you preview these textures and visualize how they will be rendered on a wall that is 72 pixels high, you will see that the default rendering will cause a problem. These textures have important details that need to be kept at the correct height from the floor. They will therefore need to have their lower unpegged flag set, so that they are rendered from the floor up.

This completes the addition of alcoves to the WAD. You can save it and try it out now, if you wish.

ADDING A PLATFORM

The next addition to the WAD is a platform inside the hexagonal room. The following shows its position and shape: another hexagon in the northeastern corner of the main room. The new hexagon should keep about the same distance from the outer walls of the main room as the pillar is in the other corner.



Set this new sector’s floor to BLOOD1 at height 32, the ceiling to TLITE6_5 at height 104, and the lighting level to 160. Put STONE on all essential texture slots.

Notice that this new sector’s floor is too high above the floor of the main room for the player to climb onto it directly. This platform is going to provide the player with the WAD’s first puzzle — not a particularly difficult one, but a puzzle, nonetheless. It is going to house some security armor (100 percent armor). You can place that now, if you wish. Put it close to the southwestern edge of the new sector, but not so close that the player will be able to reach it from the floor of the main room. It will need to be about 40 units in from the edge.

Now, to enable the player to gain the armor, you will need to provide access to the platform. You should do this by adding a step, but don’t make the presence of the step obvious: tuck it away in the extreme northeast corner of the hexagonal room, between the platform and the main wall. Players will only discover this step by walking round the platform. The careless player may miss it altogether.

To implement the step, you should add a new line connecting the northeastern corner of the platform to the nearby corner vertex of the room. Then add another new line some way to the south, connecting the platform to a point on the main room’s northeast wall.

Set the new step’s floor to FLAT20 at height 16. This provides the necessary step up to the platform. This floor texture is fairly granular and won’t require careful alignment. Now, it is often considered polite to provide clues to the solution of DOOM’s problems, and even though this is a fairly simple problem, I suggest you do that here. Let this sector provide a hint of its existence by changing its ceiling (visible from the other side of the platform, unlike the step itself) and lighting level. Apply FLAT20 to the step sector’s ceiling, and change its height to 112. Check that the lighting level is 160. Put STONE on the lower essentials and STONE2 on the uppers. The section of the original outer wall that this sector has acquired will now need a Y-offset applied to compensate for its new ceiling height. The texture will need to be moved up by the same amount as you brought the ceiling down; a Y-offset of 8 will achieve this.

This completes the first puzzle area in your WAD. Try it out, if you like.

ADDING A POND

The final addition to your WAD in this Sortie will be another little puzzle for the player, this time located out in the courtyard. The following shows the shapes to add here. Draw them now.



This new area is to be a pond. Its edges are going be made too high for the player to climb out. Unless the player is to be forced to perish here, there needs to be some form of escape mechanism.

The escape mechanism here will be a step, but not one that is simple for the player to use. It will take the form of a small island in the pond, carefully positioned so that it can be used as a step only when the player takes a run at it.

Make the pond have a floor level of -48 and a floor textute of FWATER. The platform in the water should have a floor height of -24 or so. Perhaps make the lighting level of the main pond sector reduced just to make it look a little more threatening.

You will now need to save and play test the WAD a few times to get the size and the position of your island just right. Start with it about 80 units from the eastern edge of the pond and adjust its position and size until it’s tricky, but possible, to use it to escape from the water.

When you’re happy with all of your latest additions, save your final WAD as D2WAD9.WAD.

USING STAIRS

In the previous room we discussed briefly the uses of steps. Often in DOOM WADs, steps are arranged in long runs, providing staircases between areas of widely differing floor elevations. These structures are required often enough, and are sufficiently interesting, to warrant a separate examination.

STAIRCASES

Staircases with twists and turns can provide limited visibility ahead and make for good constricted fighting areas. They also provide natural funnels to limit the attacks on a player, while providing no place to hide or run to. They are good for ambush spots, too.

Staircases generally require no special design considerations. The maximum step-up size of 24 units applies here as elsewhere. Note, though, that there is no minimum tread width: the player will climb steps with treads as narrow as one unit (provided your editor will let you draw them)!

ONE-WAY STAIRCASES

You already know that when a player moves from one sector to another, DOOM checks for a maximum step height of 24 units and a minimum gap of 56 units (the height of the player) between one sector’s floor and the adjacent ceiling. Additionally, a player can only pass into a gap that is 33 units wide. There is an interesting flaw in the method by which DOOM checks on these conditions when climbing and descending, a flaw that allows the construction of a useful addition to the repertoire of scenery elements: the one-way staircase.

As a player moves up the staircase, the engine allows them onto the lower step because there are at least 56 units (the height of the player) of clearance. If the player continues to move forward up the staircase, first the horizontal movement is calculated, and then the vertical movement. So first the player is moved forward onto the upper step, then the ceiling height is checked and, seeing that the player has clearance, the move is allowed.

However, when the player turns around and tries to go back down, the engine disallows it because it tries to once again move the player horizontally before taking the vertical change into account. Because the upper step is within 56 units of the lower step's ceiling, it determines there is not enough room for the player to enter that sector. Consequently, the move is blocked.

MONSTER BEHAVIOR ON STAIRCASES

When designing staircases, you should bear in mind that steps and stairs have an effect on the way monsters follow the player. As you have already seen, all monsters with legs share the same restriction as the player when it comes to climbing: 24 units is the maximum height they can manage. Monsters are much more reluctant than most players about descending steps, however. They will never step down more than 24 units and, in addition, they are fussy about steep stairs. Generally speaking, the greater the downward step-distance, the deeper each tread needs to be for monsters to be lured down them. Also, you may need to adjust the tread depth to suit the particular monsters you are using — the larger the monster, the more wary of steep steps they are.

Experimentation has shown that on stairs with the maximum 24-unit risers, the treads need to be at least 0.85 of a monster’s diameter before the monster will venture down them. This figure is for steps aligned with the coordinate system; those at an angle will need correspondingly larger treads. Of course, you may wish to use this fact to produce stairs that monsters are less likely to descend, so that the player can fight them from the comparative safety of the bottom!

Floating monsters are, of course, completely oblivious to the presence of steps, up or down, when it comes to chasing the player.

WAD SORTIE 10: STAIRWAYS TO HELL

During this Sortie, you will add a couple of stairways to your WAD. Start with D2WAD9.WAD and feel free to save your WAD as often as necessary during the course of this Sortie, using a sequence of TEMP10A.WAD, TEMP10B.WAD, and so on, for the names.

EXTENDING THE SOUTHEAST PASSAGEWAY

For this addition, you will find it useful to have the Grid turned on. Scroll your map so that the eastern end of the southeast passageway lies toward the bottom of the screen. The first new staircase is to be a one-way staircase heading north from the eastern end of this passageway. The following shows how the map will look after the new additions. Follow the instructions given forthwith for the most efficient way of adding them.



Start by adding a short corridor out through the north wall of the passageway. This corridor needs to be 128-units wide, so make sure that its western and eastern walls run along grid lines. Make it about 200-units long. The exact length is immaterial but, again, make sure its northern edge runs along a grid line. This sets you up for easier construction of the stairs.

Now, to catch players, one-way stairs need to be less than 33-units deep. Utilize the grid, therefore, to add six more rectangles to the map, maintaining the new corridor’s width of 128 units but making each rectangle only 32 units deep from north to south. You should now have the lines for six steps, as well as a corridor connecting the stairs to the original passageway.

Finally, add the lines for a new passageway running east from the northern end of the stairs. It should run a total of 320 units east from the western end and be 128 units north-south.

MAKING THE STAIR SECTORS

Next, change the new corridor’s ceiling-height to 128 and apply DEM1_5 to both ceiling and floor. Put MARBLE3 on the essential over the new opening and unpeg it.

Now move to the next rectangle — the bottom step — and then inspect that sector’s settings. Put DEM1_6 on its floor, and increase its floor-height to 16.

Continue in this manner, successively adjusting each new sector’s settings, before moving on to the next. Table 6.3 shows the settings to use for the sectors you are adding.



BACK TO VISUAL MODE

There are a couple of quick ways to adjust sector heights. I will show off two, starting with a return to the Visual Mode, which we have only touched briefly upon this far.

Hover the mouse over the stairway area and press Q. (The 3D viewpoint starts wherever the mouse cursor is.) Using the ESDF control scheme, maneuver around until you can see the sectors that will make up the staircase.



While pointing at a particular sector, use the mouse wheel. The sector floor height will raise or lower by 8 units, depending on which direction you scroll.

By looking around and scrolling the mouse, you can set all the staircase heights properly, albeit with the added trouble of having to maneuver.

Another, perhaps easier, method is to press Q to return to the normal view, hover the mouse pointer over a sector, and press either Ctrl+Alt or Shift, and move the mouse wheel. This will do the same thing, moving the floor (using Ctrl+Alt) or ceiling (using Shift) up and down, but maybe easier to control overall.

Either way, following the table, notice how the floor heights form an orderly progression, each rising 16 units above the previous one. The ceilings don’t follow the same progression, however — they start out 128 units above the floor at either end of the stairway, reducing to 80 units over the third and fourth steps.

With 16-unit risers, as here, a ceiling-floor height of 80 units will provide a 64-unit gap between the ceiling of one step and the floor of the next one up. Consequently, there will be no problem for a player climbing these stairs. Coming down will be a different matter, however.

The treads of these steps are only 32-units deep. In considering the downward movement, therefore, the engine will have to look two ceilings ahead of the player’s sector to determine the ceiling-floor gap 33 units ahead. Over the third and fourth steps, this gap reduces to 48 units. So, once the player is over the third step, there will be no going back.

Of course, you could have built the entire staircase using a ceiling-floor height of 80 units. In such case, it would have been a one-way stair from top to bottom. I want to provide the player with a chance to notice what is happening here, though, so the configuration you have just been given has only two “non-return” steps.