2.16.2009

Basics of effective FPS encounter design (via F.E.A.R. and F.E.A.R. 2)

I recently finished playing through the single-player campaign of Monolith's F.E.A.R. 2, a military first-person shooter with supernatural elements. In my mind, the design differences between the original game and its sequel highlight a few essential elements of good encounter design in a first-person shooter. These elements all support one primary tenet:

Give the player (and AI) options

The core experience of a good FPS such as F.E.A.R. is the dynamic conflict between the player and seemingly-intelligent, active enemies. This means that both parties need meaningful combat verbs to exploit-- expressive movement, a wide variety of attack types-- as well as spaces which encourage and highlight the use of these verbs.

The worst place to roll out these combat mechanics is in an empty hallway-- no cover, no lateral movement potential, no interesting geometry for the AIs to interact with, no strategy, no surprise. Conversely, the best space is arena-like and varied, with an emphasis on flanking opportunities. The closer any given encounter space drifts towards the hallway model, the less interesting the gameplay there is going to be.

The primary elements of a good FPS encounter space are these:

1. Varied, clustered cover. Players and AI both need useful and varied cover for any kind of tactics to arise. Half-height and full-height cover each serve a purpose, as the verticality/laterality of each is significant (full-height cover is useful against elevated enemies, while half-height cover is invalidated; full-height cover forces actors to alter their lateral path while half-height can be vaulted, etc.)

Clustering of cover is important, as cover which is too evenly distributed becomes undifferentiated and leads to a flat experience. Cover should exist as discrete islands with meaningful no-man's land between each. This gives the player meaningful moment-to-moment choices to make ("should I risk exposing myself to enemy fire in favor of running for a better vantage point?") and causes AIs to be out in the open and moving laterally to the player's view on a frequent basis as they seek new cover, allowing for a shooting gallery experience of trying to take the enemy down before he reaches safety. The idea is to create meaningful points of emphasisinstead of an undifferentiated field of scattered, equally-useful cover nodes.



The most useful cover should be placed in the arena's mid-orbital, the dense ring between the outer edge and the central point of the encounter space. This encourages the player to move into the thick of the action instead of hanging on the periphery, and leaves the central dead zone as a no-man's land that remains risky to advance through, encouraging circular navigation.


Changes in elevation are also recommended, as high ground from which to fire down on enemies can be just as useful as a solid piece of cover to hide behind. Mid-field rises also provide the opportunity to observe the space mid-fight, allowing the player to reassess the situation and adjust his tactics accordingly.

2. Circular navigability. This goes back to the "as little like a hallway as possible" point. A good encounter space gives the actors options, and encourages variability each time an encounter plays out there. This requires not just a wide hallway with islands of cover distributed throughout it, but an open arena that is circularly navigable-- one with pathways around the edges which allow defended flanking movement. This encourages the player to advance and be mobile, and allows the AI to surprise the player by swooping in on their starting position from the side. A wide hallway with cover in it still boils down to advancing battle lines, while defended flanking corridors on the peripheral encourage the actors to circle around one another, take risks ("should I risk flanking into the thick of the enemy force to gain a better close-range firing position?") and generally be active instead of sticking to a single safe point and taking potshots. Circular arenas should give the player a multiplicity of options while keeping him wary of possible enemy flanking maneuvers, dynamics which are conversely defused by the binary flow of a linear hallway no matter how wide or cover-strewn.

3. Observability. As the player approaches an encounter space, he should be able to observe its major features and devise an initial plan of attack. This means that the entry point should feature a vantage point, often elevated, that illustrates the layout of navigable space, cover points, and interactive objects (explosives, water hazards.) All relevant features of the space should be visible and readable, and any element of the space that is obscured should be intentionally so (for instance, the terminal point of a flanking corridor might be obscured to increase the player's feeling of risk in attempting a flanking maneuver by reducing his knowledge of what lies at the other end.) The player, having observed the space, may hereby think beyond arm's reach once he's in the thick of a fight by relating his current position to the overview he saw before the encounter began. Should the player die during the fight, this initial vantage point on respawn provides a reminder of the space's layout, to aid his survivability for the next go round.

Assessing a space for these high-level principles should lay a strong groundwork which can be further refined-- by line of sight tuning, strategic item placement, lighting readability-- to form the basis for an excellent encounter.

The second aspect of setting up the encounter is blocking out the placement and initial behaviors of the enemy AI that the player will be facing. This determines how the player enters the fight, and ultimately how he walks away from it. In an FPS that features expressive combat mechanics and active enemies, the best place for the player to begin the fight is right in the middle of the action; how does one encourage him to dive in, instead of plinking at his foes from the sidelines?

One way is to give the player the first move-- let him get the drop on his enemies. This ties into the observability factor, while also encouraging the player to set up the fight to his advantage and close the distance before fighting starts.

In this scenario, the player approaches the encounter space and observes his opponents standing or patrolling around in the center or at the far end, unaware of his presence. These enemies should be spread out enough that a single grenade blast won't take them all out, and having backup waiting in the wings is important. The player may observe the enemies' movements undisturbed as long as he doesn't attack or advance too close. This presents the player with options-- does he hang back on the outer ring of cover and line up a headshot on one of the enemies? Does he plant some proximity mines around the flanking corridors then toss a grenade at the group to make them scatter? Does he close the distance and open up with automatic fire just as they notice his presence? The player is allowed to choose his tactics and consider his approach. This is invaluable from a player experiential standpoint.

The opposite experience is often encountered in F.E.A.R. 2: as the player steps through a doorway into the fight arena, enemies are already aware of his presence and spraying the entry point with suppressive fire. What options does the player have now? The only valid ones are to retreat and use the edge of the entry door as cover, or to dash blindly forward into a hail of bullets, which is most often suicide. An unaware enemy is key-- it allows the player to strike the match setting off the encounter, instead of being purely reactive to his opposition's opening moves. It allows the player to take up an optimal position for beginning the fight, which a good level designer makes sure is significantly deeper into the arena than the entry door. It allows the respawning player to intentionally alter his tactics upon retry, instead of being forced to deal with the exact same setup each time.

An unaware enemy is subject to extermination by an opening headshot or grenade, but this is a small price to pay-- backup can be spawned at the far end of the arena to replace any intial fodder as a second wave of enemies advances into the encounter. The gains in player control over the fight's initial moments are worth it.

An alternate approach is the ambush-- the player observes a quiet arena, and advances into the middle, only for the enemy to pop out of hiding and attack (rappel down through skylights, jump down off of balconies, swarm in through multiple entry doors, burst through a wall, etc.) This is a fair approach in the back half of the campaign, as the player should be experienced fighting his enemy and could use some variety to encounter setups. However, the ambushing enemies should nonetheless have terrible reflexes-- enemies that pop out guns blazing will merely frustrate the player. Rappelling/door-bashing/balcony-diving/wall-busting ambushers should take a while to ready their weapons and draw a bead on the player, allowing him to make it to cover and get the first shot off. The idea is for the player to retain some initial advantage while still being thrust suddenly into the middle of an encounter.

My experience with F.E.A.R. 2 is that it unfortunately often misses the principles that made the encounters in the original game so engaging-- frequent are restrictive, linear encounter spaces without flanking corridors, precognitive enemies that begin firing on the player before he gets a chance to enter the space, and unobservable spaces without clear flow or points of emphasis. This not only makes the player's role in combat more frustrating, but makes the enemies appear less intelligent-- with fewer navigational options, they tend to remain stationary more and surprise the player less. Smart AI is only half the equation-- smart arena design is required to convincingly demonstrate your enemies' innate abilities. Hopefully the points above will help guide your encounter design towards showcasing your game's AI in the most flattering possible light, making the enemies look-- and the player feel-- as smart as possible.

18 comments:

CrashTranslation said...

As I was reading two games immediately came to mind that I think serve as perfect examples of the way it should be done. Halo: Combat Evolved and Thief: The Dark Project.

Encounters in the first Halo suffer from repetition in terms of texture and object design but each arena featured a layout and entry point designed to encourage the player to observe the situation before initiating the encounter. Aiding that the limited selection of enemy and weapon types leads to situations where, past the first few encounters, players are facing multiple types of enemies. The relative strengths and weaknesses of the enemies and the current weapon selection mean that the overall range and logical layout of the arena changes over the course of the encounter. Some enemies might be best dealt with at close range but other enemy types in the area will prevent them getting into that ideal range. Encouraging improvisation and making the player feel intelligent and resourceful when they do beat the encounter. In some of the more complex encounters it almost feels like you are fighting in multiple arenas at once as the placement of objects and cover in the environment take on different purposes depending on which of the multiple enemy types you are directly engaging with at a time.

Though the basic interaction between the player and the AI in Thief is different to that of traditional FPS titles a lot of the tenants of good encounter design still hold up. You’ve listed it as one of your favourite games so I don’t think I really need to go into how intelligently designed the levels are in that game.

What I think frustrates me most about Project Origin is that at some points it looks like Monolith were really thinking intelligently about their encounter design, only for them to send you down hallways for the next twenty minutes.

Michel said...

Thanks, this is a great post. I'm starting to get into level design and there are a ton of great resources out there that teach you how to construct levels but little information on how to design them.

You mentioned on Twitter a while ago that you wished you had more stuff to write about on your blog. Well, I would love some more of your level design insight.

L.B. Jeffries said...

Great post, I've been digging through several FPS and tactical shooter at once and this clarifies the difference I've been experiencing in all of them. Like why Gears of War's split-up portions of the map always irritate me but the diverse battlegrounds of other portions are a blast.

You might find this website a useful resource for this post and other write-ups. The guy basically posts Youtube videos of himself beating games all the way to the end while skipping nothing.

http://www.bonersgames.com/

I rely on him constantly for watching cutscenes, levels, or just writing down quotes from a game. He's a pretty big FEAR fan as well.

Iroquois Pliskin said...

This post is pretty rad, it explains a lot.

One (possibly geeky) question: when you approach level design with these best practices in mind, how do you factor in weapon design? The options that the level design offers to the player are going to be mediated by the range and power of the different tools in hand.

As Justin rightly points out, one of the things that I really enjoyed about Halo is the way that the design of the combat arenas encourages the player to experiment and improvise with the full variety of weapons by creating engagements at different distances. I thought the designers did a very good job of making the weapon design and level design work together effectively; they create this great multitiered dynamic in the combat.

Borut said...

Excellent analysis, Steve.

Two questions:

What about using the forced choke point (one doorway with enemies firing immediately you) as a tension/pacing element? It seems like its use early on would be more appropriate if you were trying to set the player on edge (caveats - the actual difficulty w/weapon balance might need to be easier than the presumed difficulty the player feels via loads of bullet tracers, audio, etc., and you might have to have back pressure to avoid keep the player from just turtling behind the single door/cover point).

And second - I'm curious, how much of this level of detail (especially w/respect to how to build spaces enabling interesting player/AI interaction) is represented/asked about in an typical designer interview? Having moved to 2K Marin last year, I'm guessing you'd have a sense of how well companies are doing at actually querying this type of critical thinking from a candidate? (My guess is they typically don't, but that may just be my industry cynicism talking). :)

Steve gaynor said...

re: Iroquois, yes, I don't get into systems design elements here, but the assumption is of an interesting spread of weapons that encourage various behaviors (such as the prox mines/hand grenades briefly mentioned) which encourage varied desired range from target for both enemies and the player. I do hold that a good FPS could theoretically be made that only features one kind of gun, but the 'expressive combat verbs' described generally fall out of the arsenal's properties in most modern FPS. Something interesting to analyze per-title on this front is which guns the enemy is allowed to use, versus which are player-only.

re: Borut, I'd say that there are definitely exceptions to the scheme described in the post, to be used for effect by the designer. I would expect that the instance of a player walking into a suppressed entryway should rarely if ever be appropriate, though. As to 2K Marin, let me just say that the views expressed on Fullbright are those of the author alone, and do not represent the policies or opinions of his employers in any way (and that the philosophy behind designing a BioShock level generally diverges from the above described model in some significant ways anyhow.)

mtvernon said...

I've never played F.E.A.R., but with F.E.A.R. 2 out I seem to be hearing a lot about it. Much of what I've absorbed has to do with complaints about the sameness of each encounter; people seem to say that the game takes place in an endless string of warehouses and office spaces. And I can see how these types of buildings might make for wonderful firefights from a design perspective. But it makes me wonder: were they abandoned in F.E.A.R. 2 chiefly because of player and reviewer criticism? How else might this repetition have been mitigated?

Danielle said...

When you spoke about circular arena-style areas with kind of a player-familiar layout, I immediately thought of the Antlion-in-the-Parking-Garage scenario in HL2:Ep1. Hooboy!

I liked that it was a familiar type of area (everyone knows a parking garage) with that scifi twist to it.

Nels Anderson said...

Most of my experience with encounter design is with RPGs not FPSs, but it's interesting how similar a lot of the fundamentals seem to be.

The most important thing is definitely providing an interesting space with options. The RPG equivalent of a doorless hallway is a square room with nothing in it but enemies. Finding ways to break up the space and giving the players(s) the opportunity for interesting options to move past the encounter.

One of the harder things to get right is providing the players are more obvious opportunity to use a certain ability (especially important with multiple asymmetric players) without it being totally hamfisted. Any thoughts that that, beyond playtesting the hell out of it?

Very interesting read, thanks for putting that together Steve.

Clint said...

Awesome post Steve, but I think you generalize it a little too much. You open by talking specifically about FEAR/2 and then you generalize through the middle and then conclude by coming back to FEAR/2.

While I think you overview of FPS encounter design is pretty sound in the majority of cases, it leaves me with the tingling feeling that you're suggesting there is an 'ideal' FPS encounter and we are (and ought to be) iterating toward it... that once we find the perfect combination of arena/mechanics we will have 'solved' the FPS. I know that's not what you mean to imply, but that's a little how I felt it was reading. Tying the generalizations back to FEAR/2 more specifically through the middle of the post will solve the problem.

Steve gaynor said...

re: Clint, thanks for the input. While I see what you mean about generalizing... I think that, except in rare cases with something like, say, The Club, the general concepts do apply broadly to "FPS." I would say that the principles of distribution of cover, circular navigability, and observability described all apply to, say, a mining camp or defended estate in Far Cry 2 (what I'd call the most authored encounters in the game) as they do to a good fight room in the FEAR series (or other linear FPS like Call of Duty or Half-Life.)

Oddly enough, a game like BioShock employs these techniques less frequently, focused as the series is on systemic distribution of enemies and crowd control player abilities. However there are generally a few spaces constructed in this way in each level of a BioShock title, as it's the best sort of place to fight a Big Daddy or stage a large setpiece battle.

It seems like I must often speak in an "I've solved it" tone on this blog, as it comments frequently take posts to mean "everything should be just like what I'm describing." I don't think that FPS encounter design is a single-solution problem, but I have noticed a few properties common to all the best FPS fight spaces I've played in.

noethis said...

Wow, great analysis. While I've thought of FPS combat in terms of verbs before; and I've thought a lot about how the level design impacts the combat, for some reason I never connected the two. It makes perfect sense that circular navigability affords a new verb such as "flank" and that verticality affords verbs such as "taking cover" and "splash damage" (ok, not a verb..).

At first I was going to mention that these concepts only apply to tactical combat and not to other types of FPS combat such as against large melee creatures, but, taken generally, they do apply.

quicksavethoughts said...

There was one fight in FEAR 2 which came close to what you've posted, the one against the controled cloned troopers in the training arena... and that was maybe one of the most interesting encounters in the whole game.

AJ said...

Interesting stuff. But why do you assume players are male (ie, male pronoun throughout the piece)?

Steve gaynor said...

I prefer not to qualify the generic male pronoun with disclaimer language. It always seems patronizing and redundant to me. I trust everyone to understand that both men and women are present and involved.

Magnus Jonsson said...

Well written. I found it very informative. The notion of having an option before engaging the enemy really hit home with me. It's definitely something I'll take with me back to my own work.

Steven said...

Thanks for the post, keep up the good work. I would be really interested for you to pick out a few specific encounters from various games and apply these concepts to show they work or do not work, maybe with an aerial view of the map for reference. If you have the time, of course...

Ryan Wiancko said...

Was just discussing the differences between FEAR 1 and FEAR 2 with Trent Polack tonight on twitter and we certainly both agree that the FPS encounters and level design in FEAR 2 lack most of the elements that made FEAR 1 so brilliant. Trent's opinion is that it could have been a reaction to move FEAR 2 more towards a COD style of gameplay in response to how poorly FEAR 1 was received on consoles.

Do you feel that there are elements, many of which you described here, that work beautifully on a PC, or with a PC gamer, but have a negative effect in a console environment? It's been the sneered for years from us PC gamers in our lofty towers that console games are always dumbed downed versions of their PC counterparts, but would this be an instance where the reception of FEAR 2 on consoles points that it is necessary to eliminate or 'dumb down' elements of a successful PC shooter to make it more palatable to a console audience?

If so it might be an interesting study to find out the elements of a successful PC FPS vs a successful Console FPS