[TerranUp16]

This is the first thread in a series of threads I want to start. I call them... "Design Discussions". The idea is pretty much to discuss- between other designers, developers, and gamers- design concepts. Discussions will range from analysis of a specific piece of an existing game's design to an aspect of game design theory to a new design concept. This first topic is going to be an analysis on a microdesign element that has been incorporated into numerous games. The idea of the discussion is to understand the purposes behind its implementation and potential usages of it.

So, to start things out, we're going to talk about bullet knockback. By this, I mean that when when you get hit by a bullet you get shoved backwards. This seems to be almost a standard feature of the Source engine as it has been incorporated into Half Life 2, Team Fortress 2, CounterStrike: Source, and Portal as well as many Source mods (the Timesplitters series is another notable FPS series that utilizes bullet knockback extensively). In some ways, it seems unremarkable and natural because your character is getting hit by objects going at insanely high speeds. However, do the physics and generally this is unrealistic- while a bullet may cause a person to involuntarily take a step back, the bullet itself is generally not massive enough to impart a force significant enough to shove a person backwards. Yet in games with bullet knockback it's not unusual to see a character performing a running animation towards the direction from where the bullets are being fired yet the character is being moved backwards by the bullets. We could easily dismiss such a feature as a logical fallacy on the part of the designers or on the part of the physics engine utilized (ahem, Havok, ahem). But we're going to take a look beyond that and look for the other reasons why such a feature might be desirable.

Let's first consider bullet knockback from the point of view of the character that is being knocked-back. The first thing that the user will notice is that the character is being knocked back. The user will next connect that knockback to the bullets impacting the character's body. The bullet knockback, therefore, becomes an interface tool that indicates to the user that bullets are impacting their character. We can additionally note that shot-guns, rockets, explosions, etc... will generally produce more significant knockback and thus will provide additional feedback on what is hitting the user (a steady stream of knockbacks generally comes from a machine gun while a series of longer-interspersed but larger knockbacks are likely from a sniper rifle or magnum or etc while a single big knockback is likely from a rocket). A secondary accomplishment of this is that the knockback itself is arguably a dramatization of the damage the user is taking, but in dramatizing that the user can tap into what taking a bullet really feels like, thereby increasing the user's immersion in the game.

From a gameplay standpoint, bullet knockback can provide a penalty to a player for allowing him/herself to be hit, particularly in a continuous manner. This can reinforce the need for cover or at least the need to be near cover. It can also prevent a player from just brute-forcing a situation. For example, it's extremely tough to use a Pyro or melee weapon to destroy a Sentry Turret from the front in Team Fortress 2 even if a Medic is healing (or even ubering) the user because the bullet knockback makes progress extremely tough. This forces the player to find more creative, tactical ways of decommissioning the turret. Half-Life 2 utilizes turrets and snipers in a similar manner, impressing on the player the importance of utilizing cover and grenades. Likewise, Portal stresses the use of cover (via boxes) and the use of the portal gun. In a game/mod like Zombie Panic! Source, the bullet knockback that Survivors can impart on Zombies largely prevents Zombies from just shamelessly bumrushing survivors and relying on high health to brute-force a kill. Instead, it encourages Zombies to actually stalk Survivors and rewards Zombies for finding ways to get at Survivors' backs. It also penalizes Survivors for leaving their or their allies' back(s) open.

Crysis, on the other hand, is an interesting example of an FPS that shuns bullet knockback for other methodologies of accomplishing varying design goals. In terms of interface and immersion, Crysis utilizes post-processing (though many games that utilize bullet knockback do as well) to blur the screen and tint it red. Crysis also incorporates sound effects such as grunts to forward these goals. In terms of gameplay, taking a heavy amount of damage in a short amount of time will temporarily cripple players from shooting accurately and at a normal rate of fire. This also plays to immersion. Thus, Crysis fulfills many of the same potential goals as bullet knockback without actually using bullet knockback.

So while bullet knockback may just be a logical fallacy on the part of the developers, it is equally possible and potentially more likely (considering that it is not a consistent logical fallacy across games of even the same genre) that bullet knockback is instead a design choice utilized to forward interface, immersion, or gameplay design goals.

Have another usage or example of bullet knocback you'd like to point out? Want to discuss an alternative? Want to comment on the pros/cons? Then REPLY!

[Avalon]

I tend to find it's overly ridiculous in ZPS, but then again like you said it's sort of necessary to promote better gameplay. I don't think a zombie would mind if his vision blurred when he's got 250 health and can infect people, and doesn't really need to aim when he attacks :P

[TerranUp16]

Avalon said:

I tend to find it's overly ridiculous in ZPS, but then again like you said it's sort of necessary to promote better gameplay. I don't think a zombie would mind if his vision blurred when he's got 250 health and can infect people, and doesn't really need to aim when he attacks :P

Yep. I think it works really well in ZPS, but admittedly I'm still not entirely convinced that it was done purposefully, xD Since it seems like it's a core component of the Source engine, they likely would have needed to remove it manually which they may originally have forgotten to do or just not felt the need to. Of course, the latter could be grounds for it being an informed design decision, and I suppose by this point it's likely that somewhere along the way they made a conscious decision to leave it in rather than to take it out, particularly with its recent transfer to Steamworks as that would have been an element of polish for them to consider if they felt it was a useless feature.

But yeah, ZPS is undoubtedly one of the best examples of its usage that I've seen so far.

[ninjafish]

Avalon said:

I tend to find it's overly ridiculous in ZPS, but then again like you said it's sort of necessary to promote better game play. I don't think a zombie would mind if his vision blurred when he's got 250 health and can infect people, and doesn't really need to aim when he attacks :P

The problem with the knock back in zps is that its the same in both game types, in the game mode where zombies have infinite lives and humans have to complete objectives, the knock back is appropriate.

The other game type where zombies have a finite number of lives typically 20, the goal of the humans is to basically hole up in a room with a bunch of ammo and kill zombies. The knock back is many times too much for zombies to over come and it basically becomes a group of humans hunting zombies with automatic weapons which have the most extreme and unavoidable knock back. In this game type, its basically your lives vs their ammunition, which ever one runs out first determines the winner. Even worst there isnt a standard infection rate for the alpha zombie across servers, so you get some admins who think a 10% infection rate is appropriate, and then you run into games where a less then perfect alpha zombie fails to kill or infect anyone leading to very boring games where survivors are hunters from the start of the game.

[TerranUp16]

Been playing a lot of the non-mission game type and still feel like knockback is good. Rarely have the survivors managed to hole-up in a room well enough to prevent a crafty zombie from taking at least one out in the early stages of a game. Plus, if they stay holed-up in the room, even a single zombie has plenty of lives to force them to waste a crapload of ammunition. And once numbers start turning in the zombies' favor, if the survivors just hole-up in a room it's all about numbers and shoving the convert zombies in front while the carrier comes in last after the zombies in the forefront have absorbed most of the bullets and damage. And if the survivors do hole-up in a room, of course the zombie can just wait outside until everyone in the room gets bored. Granted, that is arguably a design flaw but it's one that typically works itself out. Even when a zombie is hunted, it's just a matter of that zombie becoming an Alien ;)

Still, on the whole it's balancing the need to keep zombies from just mobbing survivors with no tactics whatsoever against the need to break stalemates and keep zombies dangerous. On the whole still, the game is survivor-oriented so it's also meant to reinforce that is the survivors are playing well/right that they should do well (so checking your corners and ensuring that zombies can't sneak-up on you should be rewarded positively- but that's going to require a team effort).

[Avalon]

Well, since hosting a server I've learned that 10% is the default infection rate. I'll look for the commands to see if infection and knock back can be modified. Alternatively, does anyone know how to install MetaMod/AMX onto a server? The instructions tell me to create an addons folder within my source game folder, and then in the launch command properties add a line that directs it towards the MetaMod/AMX module. Hasn't been working so far, which sucks because I think I can get some good customizations in for any source game.

[ninjafish]

Avalon said:

Well, since hosting a server I've learned that 10% is the default infection rate. I'll look for the commands to see if infection and knock back can be modified. Alternatively, does anyone know how to install MetaMod/AMX onto a server? The instructions tell me to create an addons folder within my source game folder, and then in the launch command properties add a line that directs it towards the MetaMod/AMX module. Hasn't been working so far, which sucks because I think I can get some good customizations in for any source game.

10% is terrible, at the very least it has to be 15%, i prefer 20% though