[Vanilla Level Editing] Lesson 12: Populating Your Doom World

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By now, you should have a WAD in which the map is nearing completion. It will not yet have much of a population, however — a few monsters on the higher skill-levels to help you test out some areas, a suit of Security Armor, and a few keys is about all.

In this room, we will set about changing that. Here, you will be led through the steps involved in populating your WAD for real. First of all, you will be shown a strategy for deploying the enemy forces — and for laying out caches of arms and other supplies for dealing with them. Methods for implementing different difficulty levels will be discussed, and mention made of other uses for the game’s difficulty settings. There are also examinations of the way in which DOOM’s creatures behave and the way in which sound propagates through a WAD.

In addition, this room’s final Sorties will provide you with practical experience in the initial stages of the process of populating your DOOM world.

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PLANNING THE ASSAULT

Many designers spend long hours drawing up the geography of their playing arena, getting the layout and appearance just perfect, only to spoil everything with careless — one might even say thoughtless — selection and positioning of enemies and resources. The distribution of the creatures and artifacts that players will encounter is at least as important — many would say more so — as the layout of the geography itself.

As always, the key lies in the planning. You should aim to:

• Plan carefully
  
• Progress logically, and
  
• Play-test thoroughly
  

Apply these guiding principles to the populating of your WAD as to every other aspect of WAD design.

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PREPARING TO POPULATE THE WAD

By the time you start populating your WAD, you should have a clear picture in mind of the way you want the WAD to play. You should know what each of the areas in the map is like and what function each is to serve in the grand scheme of your level. You should have a fair idea of what is to happen in each area and in what order events should occur. If you don’t know these things before you start laying out the denizens of your WAD, they are unlikely to contribute much to the way it plays.

So before you start placing any items, take a good look at the geography of your WAD, clearing up in your own mind how you want each area to contribute to the level as a whole. Sketch out the way that you feel play should progress. Then take a run through your empty WAD, trying to visualize the way it will all work. Only when you’re confident that you know what you want should you set about trying to achieve it.

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THE NATURAL ORDER OF THINGS

The secret to laying out a WAD successfully is largely one of sequence. One of the main difficulties in populating a WAD is achieving a balance between the forces that players will encounter and the means of disposing of them. You will find that it is much easier to achieve this balance if you do things in the right order. Here is one possible workflow:

• Player starts and keys: Begin by laying out player-start positions and keys. This determines the flow of the WAD from the outset.
  
• Essential obstacles and artifacts: Next, place those obstacles (and any artifacts) that are essential to the control of flow. These can be regarded as part of the geography. Leave out the decorations at this stage.
  
• Enemies: When the flow of the WAD has been established, place enemy forces in the principal combat areas. This enables you to see how the forces you envisaged behave in the space you have provided for them.
  
• Weapons and ammunition: Once you are happy that the monsters behave as you’d like, concentrate on providing the players with the weaponry needed to dispose of them. n Power-ups: Having provided your players with creatures to fight, and the means of fighting
  them, you should now make sure that they can live long enough to do it.
  
• Bonuses: Most players see collecting the bonuses as secondary to slaying the monsters. Lay these out, therefore, after the main battle scenarios have been completed.
  
• Decorations: Add any final atmospheric decorations that you feel enhance your WAD. Don’t overdo it!
  
• Extras: When you’re happy with the main areas of your WAD, consider adding a few wandering extras to the enemy’s principal forces, just to keep your players on their toes.
  

Each of these stages in the laying out of a WAD will be examined shortly. Between each stage, test thoroughly and don’t be afraid to go back a stage or two if need be to change or refine things that you have doubts about.

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EFFECTS OF OVERPOPULATION

Before you dash off to start filling your WAD with monsters, you should be aware of the consequences of overpopulating your DOOM world. Placing too many Things around your map can overload DOOM in two ways. The first is through Sprite overload. This occurs when there are too many Things in view at one time. The second problem you may encounter is save buffer overflow. This occurs when there are just too many changeable items in a WAD.

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SPRITE OVERLOAD

Sprite overload is an unpleasant effect that can occur in areas that use a lot of Things — such as hordes of monsters all attacking simultaneously, or lots of decorations, or both. In laying out a WAD, you should always bear in mind that DOOM can only handle the display of 128 Sprites — enemies, decorations, ammunition (either on the ground or in flight!), bonuses and so on — simultaneously. If there are any more than this, you will find that they all wink in and out of existence during play. The more Sprites there are, the longer each spends invisible.

Avoid this effect by limiting the number of Things in view at any one time. Cut down on the number of monsters (you can make combat tougher by reducing armor, ammo, and health availability, or by increasing the toughness rather than the number of enemies) and resist dense pockets of unnecessary decorations.

A maximum of 128 Sprites in view may sound like a major restriction to the more bloodthirsty of you, but remember that, generally, the game engine will have slowed to a crawl, trying to keep track of all of these Sprites long before this limit is reached! However, if you really want these quantities of monsters, take steps to keep them spread out around the player so that they can never all be in view at the same time. The game will still slow down, but the WAD should not suffer from the disconcerting effect of winking Sprites!

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SAVE BUFFER OVERFLOW

The buffer that DOOM uses when writing a saved game to disk is not very large. If your WAD provides the game engine with too many items that can change during the course of the game — basically any items that the player can acquire, kill, destroy, move or change in any way — you risk causing this buffer to overflow. The result is a game that cannot be saved—and some very frustrated players!

It is difficult to gauge how big a WAD can get before causing this condition, mostly because it is impossible to judge precisely just how much space DOOM will need. Developing your WAD by degrees, and regularly trying to save games while in play, will keep you assured that you are not overstretching the engine’s capabilities in this area.

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USING THE DIFFICULTY SETTINGS

It is common for WADsters to feel that it is not necessary to create a design for each of DOOM’s difficulty levels. They argue that most players will be using the “Ultra-Violence” mode anyway, so why bother? In my opinion, such a view is misguided.

Certainly there is little point in implementing an easy version of your WAD for first-time players. You can reasonably expect all of the users of your WAD to be seasoned DOOM players. (Why would they be playing an add-on WAD, otherwise?) Remember, though, that not all players have the same abilities or preferences. Your WADs will be better received if it is possible to vary the level of difficulty to suit a range of playing skills and styles.

Bear in mind, too, that you are not constrained to using DOOM’s difficulty-level settings merely to vary the WAD’s survivability. Used imaginatively, Things’ skill-level flags can work constructively to prolong the useful life of your WAD, by providing players with scope for more varied play than graded WADs can provide.

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GRADED PLAY

As already noted, the provision of graded play can make a WAD appeal to a wider audience. When working on such a WAD, it is often best to lay it out at skill-level 2 (“Hurt Me Plenty”) and to playtest this first. Make this setting hard enough to push your own DOOM-playing capabilities—it should be a struggle to complete the level. Work out next what should appear at skill-level 1 (“I’m Too Young To Die” and “Hey, Not Too Rough”) to produce something that is a comfortable play for you. Finally work on skill-level 3 (“Ultra-Violence” and “Nightmare”), making this very difficult for you to play.

Laying a WAD out like this can be time-consuming and tedious. But you should find that the result is a WAD that will have at least one level to suit any player. Some tips on what you can do to give your players a harder time are given in later sections of this room.

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VARIED PLAY

If you are more interested in producing a WAD which is uniformly tough to play at all difficulty settings, you can still use Things’ skill-level flags to introduce other variations into your WAD. You can use the flags to control or vary the occurrence of most Things with skill level. Remember that this applies to obstacles, key-cards and teleport destinations, as well as the more obvious categories of monsters, weapons, and power-ups.

You can therefore use these settings to change the flow of a WAD completely from one difficulty setting to the next. You can use obstacles at some levels of difficulty to block corridors that are open at others; move the keys around and generally employ the skill-level flags as a cheap way of producing three different designs within the same basic map. This can greatly increase the lifetime of your WAD, providing its players with three WADs in one, with the need to find new ways of tackling each difficulty level.

You can also vary the game style, while at the same time keeping the play tough enough for even the most seasoned DOOMster. Use different mixes of monsters, weapons, and power-ups at each skill level to provide another element of variety for your WAD’s players to select.

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POSITIONING THE MISSION IN THE EPISODE

Another point you may need to consider when planning the population of your WAD is where it will be played within an episode. Most PWADs replace an episode’s opening mission—few people will want to play all of the way through a familiar mission to begin a new one. You may, of course, be building a new multimission WAD either from scratch yourself or by contributing one mission to a collaborative project.

Planning for players arriving from earlier levels can be tricky. You do not know whether players will arrive barely alive and in need of some power-ups pretty quickly, or whether they will arrive fully armed and super-fit, having saved the previous level’s Soul Sphere for last.

Usually, though, you will know what weapons were available to the player on the previous level. Generally speaking, you should assume that these have been obtained and can plan your own WAD around this assumption. If having those weapons then becomes vital to the completion of your own WAD — it doesn’t have to, of course — you should make sure that your WAD will supply additional ones for players who missed them earlier.

The safest option is to make it immaterial how a player is equipped on arrival and to provide everything necessary to complete your own level.

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A DEPLOYMENT STRATEGY

A suggested sequence for laying out the creatures and artifacts in a WAD was presented earlier. Each of the steps outlined then will now be examined in more detail, to enable you to see the overall strategy for the successful population of a WAD. Let’s start by considering a map’s flow of play.

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CONTROLLING FLOW

Hopefully, your geography has been planned with consideration of its general flow in mind. Before you come to populate in earnest, though, it is worth taking a final run through it, looking at the way it all interconnects and imagining how the player might progress from one area to the next.

Consider what order players might choose to do things in. Can they try variations in the order in which areas are tackled? If they do, will this alter the way in which your planned encounters occur? It is easy to lose sight of the big picture when you are working on the geography of each room. Take the time, then, to try to imagine each area in use and how it fits in with what should happen in other areas; this will enable you to refine your thinking (and hence your design) of each area and maybe the WAD as a whole.

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PLAYER START POSITIONS

When you are reasonably happy with the layout of the lines, decide where a player is to start — you should really have planned this from the outset, but you may want to revise your thinking after walking through the WAD a couple of times. Unfortunately, you cannot use the skill-level flags of Player 1 Starts to have the player begin the level in different places. If you attempt this, DOOM will use only the last of the Player 1 Starts that you placed, no matter what difficulty level is selected. Each of the other positions will be occupied by a static "voodoo doll" of the player. Voodoo dolls can be used for various special effects, but you should pretty much never have one sitting in the main field of play.

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KEY-CARDS

Use keyed doors to divide a WAD into self-contained areas, or to control the flow of play so that areas are tackled in an appropriate order — to ensure that the tougher monsters are not encountered until a player has had a chance to acquire some heavy weaponry, for instance, or to prevent a player from leaving until all of the WAD’s puzzles have been solved.

Lay out the key-cards in the positions they need to occupy to facilitate the flow pattern you envisage. The locations of key-cards can be made to vary with skill level. Utilize this either to make the cards harder to obtain at higher skill levels, or to spring different traps as cards are acquired. If you wish, you can even alter the flow altogether by changing the order in which the cards can be obtained.

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OTHER ESSENTIAL ARTIFACTS

At this stage you should also lay out any obstructions that are important to the flow of the game. You can use certain items of decoration — fire-sticks, columns, and so forth — as obstructions in gaps that you want to let players shoot but not pass through. Once again, you can control the use of these obstructions at the different skill-level settings, thus blocking off some corridors and opening up others to change the interconnections of your WAD.

Consider also whether any special power-ups might be needed for the successful playing of certain areas of your geography — Light Intensifying Visors for the dark areas, for instance, or Radiation Suits. Place these items at this stage to help your playtesting. Again, the skill-level flags can be used to control the available quantities as well as the locations of these items. You might want to reduce their availability (or remove them altogether) at the higher difficulty settings.

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TESTING THE FLOW

Once you have laid out the various items that will control the flow of the game, try taking another run through it. Aim to make your way as quickly as possible from start point to exit, taking whatever route is required to collect all the keys and make it to the exit. Doing this at this stage may well identify areas that the player doesn’t need to visit — and that therefore contribute little to the flow of the game. If you had intended those areas to figure more prominently in the game, you may need to redesign the flow. Try moving the keys around, or changing the way the doors are keyed, for instance. Or maybe you will just want to use those areas for the positioning of secrets. (Players shouldn’t need to go everywhere in order to complete a mission, of course — only to complete it with a full score.)

After any redesign, run through your level again to check that everything flows as you had intended. Try to imagine the sequence of predicaments that players might find themselves in as they work through the WAD. By the time you have done this a few times, you should have a clear picture of the way your WAD is going to work and where most of the monsters should be.

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DEPLOYING MONSTERS

The choice and deployment of the forces that your players will encounter require not only a full appreciation of each enemy’s individual characteristics, but also an understanding of the basic behavioral patterns common to all monsters. Some of this knowledge you should already have gained from playing the game itself. Some additional factors which influence the movements of monsters during play, and the options open to the designer for controlling them, will be covered in a later part of this room. For now, though, I shall just discuss in general terms tactics for the deployment of monsters in battle zones.

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CHOOSING THE TYPES

The bulk of a WAD’s monsters should be introduced in a structured way. Work around your WAD, implementing the main battle areas first. For each zone, determine the principal type of combat you wish to inflict upon your player. Decide the main mix of monsters and their quantities, taking into account their basic behavior and characteristics, the way they mix (or don’t) with each other, and how much space they have around them in which to fight.

If the structure of your WAD forces areas to be tackled in a particular sequence, make sure that you keep this in mind as you place the monsters. Try to make each encounter harder than the previous one, and don’t present players with the tougher monsters too early unless you also intend them to have acquired some heavy weaponry as well.

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GRADED ENCOUNTERS

When using monsters to produce graded play, don’t assume that just throwing more and tougher monsters into the fray will always make things harder for the player. It might, but more often than not, it won’t. This tactic frequently produces an unstable mix of monsters who are happy to spend their time fighting each other rather than the player. Often a player will have little to do apart from keeping out of the way, and picking through the corpses afterwards!

There are better ways of making levels tougher than by loading them up with extra monsters, and you should resist the temptation to do this. In particular, don’t use the skill-level settings simply to satisfy players who might want a bloodfest. Let them use “Nightmare” mode.

Remember, too, that giving some players certain types of monsters to fight will simply supply them with additional ammunition and weapons! Most players view Sergeants as just another supply of shotgun shells, for instance. On the other hand, Imps used in large quantities will give players a hard time. These are frequently employed because of their tolerance of their own kind’s poor aim — and the fact that they provide the player with nothing afterwards.

As you populate each area, therefore, it is imperative that you try out the WAD to see how the mix of monsters you are using behaves.

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TESTING THE MIX

Testing your mix of monsters should not consist of wading into battle with the full protection of degreelessness and lots of very happy ammo, just to see how easy it is to waste everything in sight. Rather, you should mostly be running amongst the baddies, shooting at them just enough to keep them interested in you, and observing how they behave together.

Use IDDQD to stay alive while you see whether any sort of status quo is maintained if you don’t fight. Try to determine whether the monsters would quickly surround and overwhelm a player during proper play. Or will their buddies do all of the dirty work if a player can just keep moving? Check that you are giving the player the sort of hard time that you had planned.

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ADDING VARIETY

When you think you have one area right, you can move on to populating the next. Aim for variety in encounters with monsters — not only in the types and quantities of enemies, but also in the character of the fight. Your geography should already have been designed to vary the sizes of combat arenas and to provide a mix of light levels. Make the most of these variations in your monster deployments. As well as rooms full of foes, arrange for some monsters to hunt for players while others lie in wait. (We’ll look at some ways to arrange this shortly.)

Above all, don’t make everything predictable — leaving a dark and twisting corridor altogether devoid of monsters can be a very effective way of raising a player’s pulse rate. Aim to balance the suspense, the surprises, and the episodes of total carnage. Try to avoid the kind of shoot-’em-up WAD that bores players with its predictability long before they finish it.

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WEAPONS AND AMMUNITION SUPPLIES

When you have most of the major battle zones populated with monsters, you can turn your attention to the weaponry that is required to deal with them.

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GAUGING SUPPLY

One way to find out how much ammo you need to supply is to play each area in turn with the IDKFA code invoked (and IDDQD if necessary), taking note of your ammunition stocks before and after each main combat event. This gives you a chance to try the effects of fighting with different weapons, too. You may find that certain weapons make fighting easier, while others are a positive hindrance (such as the rocket launcher in confined spaces). Use this information to decide what weapons to make available at each difficulty level. Make levels harder by limiting the power or suitability of weapon supplies, as well as by reducing availability (and accessibility).

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RELEASE RATE

Once again, consider the flow of your WAD in deploying weaponry — use the secret places for the real goodies, so that the more observant players benefit the most. Make sure, though, that players can obtain the weapons necessary for survival if they look and work hard enough for them.

In higher difficulty levels, you may want to leave it entirely to the monsters to supply ammunition and certain weapons such as the shotgun (and, in DOOM II, the chaingun). You can also make things tougher by limiting the amount of ammunition players can carry — do not provide Backpacks. This is a far more effective way of increasing the difficulty of a mission than increasing the monster count — half a dozen Imps can be quite a challenge if a player is down to bare hands!

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ADDITIONAL ITEMS IN THE ARSENAL

This stage of laying out the WAD is often an appropriate time to consider the placement of barrels. These are important elements of the players’ (and the enemies’) arsenal. Not only do they act as a powerful weapon, but barrels also represent extra hazards in confined spaces. They are useful for creating temporary obstructions that players can move (if they think to) and are a good way of preventing players from being able to creep about the WAD without waking any monsters who may be around.

Barrels are useful devices for creating variation across the skill settings. Place them close to monsters to favor the players — or next to likely hiding places to make players’ lives more hazardous.

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TEST IT ALL AGAIN

When you’ve completed the layout of your WAD’s arsenal, try playing it again using only what you’ve laid out. Use the IDDQD code as necessary to stay alive, but don’t award yourself any additional ammo at all. Refine your monster placings and barrel spacings, and adjust the weaponry available until the WAD is satisfying to play.

You can then start thinking about the power-ups.

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POWER-UP ARTIFACTS

Power-up artifacts will be necessary for your players to survive the ordeals of your WAD. The correct deployment of these can often make or break a WAD.

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GAUGING WHAT’S NEEDED

You can determine the amount of health that players are likely to expend in their battles by using the same technique you used to determine ammunition requirements — play the WAD without the IDDQD code and note how much health is consumed in each encounter. Lay a temporary stockpile of health power-ups — berserk packs are good here, because they give 100-percent health — somewhere central in your WAD so that you can grab a quick boost between each encounter. (Don’t forget to remove these again when you’ve finished with them.)

Consider where you might place Stimpacks and Medikits to provide major replenishment of the player’s health. Decide whether you want to provide the player with a health boost before a heavy encounter — this often acts as a warning of something bad ahead — or make them wait until (or if) they have survived the ordeal before offering the chance.

Generally, you should reserve the major bonus items, such as Soul Spheres and blue Combat Armor, as rewards at the end of large-scale combat, or tuck them away in secret locations.

Make levels harder by reducing available health. Provide a single large power-up quite early, say, and then only smaller boosts from then on. Players will then have to sustain little damage if they want to make it to the end of the mission.

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SPECIAL POWER-UPS

Some of your planned encounters may require the more powerful artifacts, such as Blur or Invulnerability — make sure these are positioned appropriately (which is not to say easy to find or to easy to obtain, of course!). Do this at this stage, if you didn’t do it earlier.

It is often a good idea not to place these too close to where the action that you think requires them will occur. Let them be squandered the first few times the WAD is played, by encouraging players to take and use them too soon. You can achieve this by positioning such artifacts in junctions, or close to secret connections to the appropriate battle area. This prevents players from associating the artifacts with the route to any particular area. Make it ambiguous how such artifacts might be needed. Give players the opportunity to try out their use in different ways. Don’t forget to try all of these different ways out for yourself, too, of course!