HTML Version 2.1.1, August 15, 1999

Frequently Asked Questions About the BFG9000

By Tony Fabris

Contributors, in alphabetical order:

Doug Bora ....... Content, Editing, Proofing
Tod Bouris ............ Content, Playtesting
Bernd Kreimeier ...... Recent Technical Data
Chris McAllen ......... Content, Playtesting
American McGee ........ Early Technical Data
Randy Pitchford ........ Quake 2 Information
Dean Stretton ..................... Proofing


This text is intended to give the public information about some elements of the computer games Doom, Quake, and their sequels, by id Software. This text was not written by id Software, so bugging them about its contents is probably a very bad idea.

Additionally, the computer games referenced in the text are of an adult and graphic nature. In no way is this text intended to promote violence of any kind. Any references to violence in this text are meant in relation to the playing of the computer game, not real violence. The author is adamantly non-violent.

Additionally, this text is being presented in the form of a computer file. Any illegal or damaging activity related to the use or transfer of this or any other computer file is not the responsibility of the authors.

Trademark Information

All specific names included herein are trademarks and are so acknowledged: id Software, DOOM, DOOM II, THE ULTIMATE DOOM, QUAKE, QUAKE 2. Any trademarks not mentioned here are still hypothetically acknowledged.

Copyright Notice

This article is Copyright (c) 1998 by Tony Fabris. All rights reserved.

You may make and distribute copies of this work in original form, so long as the copies are exact and complete, the copies include the copyright notice in its entirety, and the copies are in electronic form. You may not charge any sort of a price or fee relating to any copies of this work in any form.

Table of Contents

Section 0 - Introduction Section 1 - BFG Basics Section 2 - The Direct Hit Section 3 - The Blast Area Section 4 - Deathmatch Techniques Section 5 - Submitting Corrections Appendix A - Quake Mods Appendix B - Quake 2


Well, I just got my reply from Bernd Kreimeier, so I think the last few missing details about the BFG's behavior have finally fallen into place.

He was extremely helpful, and pointed out a couple places in the Doom public code release that answered my questions. Specifically, we've now got the exact time delay, damage, and range limitation information. Thanks, Bernd!

And to add icing to the cake, Randy Pitchford and I have nailed down the last few details about the Quake 2 BFG10K, so I've fleshed out that section as well. Thanks, Randy!

This BFG FAQ has been a very unique project for me. Its development cycle has spanned over two years, and it's been through many revisions. Thanks to all the folks who e-mailed me about it, and the folks who contributed.

I think my favorite part of this whole thing was seeing all the other "Doom specific weapon" FAQ files appear on the net after the BFG FAQ came out. All the way down to the "Pistol FAQ". The first one, I recall, was originally intended as a joke... it was a "Rocket Launcher FAQ" that started out as a satire of the BFG FAQ. It was hilarious, and even had satires of the ASCII diagrams. Now these files are actual legitimate FAQs in their own right.

When I first undertook this project, it was simply because I couldn't get a straight answer to the question, "How does the BFG work" on usenet. Now it's taken on a life of its own. With the Christmas release of the Doom source code (Thanks, id!), I guess the whole thing has come full circle.

It's been a fun ride!

Section 0 - Introduction

0A. What is this FAQ about?

A FAQ file, stated simply, is a Frequently Asked Questions file.

This FAQ file describes, in as much detail as possible, the behavior of the BFG9000 weapon in the MS-DOS version of the games Doom, Doom II, and The Ultimate Doom. It is not intended to answer general questions about the game itself. Please refer to the other FAQ files for help in other areas of the game. You can also frequent the* newsgroups for more information.

We began writing this FAQ out of necessity. We were frustrated at the apparent inconsistencies in the way the weapon seemed to behave during game play, especially during deathmatches. There were times when we would get killed by the weapon when we thought we were completely safe. Conversely, there were times when we thought we had used the weapon correctly against an opponent, but they walked away unscathed.

Our intent is to provide players with enough information to attack effectively with the BFG, and to correctly defend against it in a deathmatch. Our hope is that this information will give players a new attitude toward the weapon. We want to transform it from "The weapon we love to hate" into "The thinking man's weapon".

With the 1997 release of both the Doom source code and the sources for the Quake 2 game DLL, this FAQ will hopefully provide accurate information for all versions of this unique weapon.

0B. How was the information in this FAQ obtained?

Initially, the information came from playtesting Doom. We would simply theorize about the weapon's behavior and then test the theory on the network.

Testing was performed on Pentium computers running the MS-DOS versions of Doom II and The Ultimate Doom. Tests were done both in single player mode and in 4-player deathmatch mode. Testing was performed on the regular levels as well as custom made levels. In some cases, a special .WAD file was created to test situations that would be difficult to reproduce with the regular levels.

At one point early in the development of the FAQ, we exchanged some emails with American McGee at id Software. He filled in some very important details for us-- for example, until American told us about it, we didn't know that the game used a set of damage traces to calculate blast area damage. His help was invaluable in putting this FAQ together and getting it off the ground.

Recently, I was able to ask Bernd Kreimeier some specific questions about the code. His answers, I hope, have cleared up any ambiguities in the details.

0C. How accurate is this information?

Fairly accurate. Accurate enough to base your playing strategies on. However, it has not been tested with every single version of Doom, and there may be differences among platforms.

Then there's the issue of the Doom public code release. That code was "cleaned up" by Bernd Kreimeier, who was given the sources by id Software to prepare it for a public release. Bernd tells me that he did not change the BFG code in the cleanup process, but the sources are from a later date than the original commercial releases of Doom and Doom 2. In his words:

      It is the January 10th, 1997 version - a few TNT/Plutonia
      mod's have been done in this code base, but I am in no
      position to confirm whether this affected the BFG code.
      I never looked at that part of the code, nor changed it.
Until I hear otherwise, I'm going to assume that the public code release contains the same BFG behavior as the commercial releases. Everything you see in this FAQ will be based on the old playtesting we did in 1995, cross-referenced against the sources found in the 1997 public code release.

Finally, now that the folks are modifying, compiling, and releasing their own versions of Doom, who knows what they might change? The BFG was an infamous feature in Doom, and will likely be the first target for modifications. So read those README.TXT files before you play a modified Doom.

Despite all of that, some items in this file may still be conjecture. Please see section 5 if you suspect this FAQ contains erroneous information.

0D. Where is the latest version of this and other FAQs?

The latest Doom-related FAQ files and other documents can be found at all of the Doom mirror FTP sites. The central location for the Doom mirrors is at However, that site is usually quite busy, and you may need to locate another mirror site from which to download. Listing all the mirror sites is beyond the scope of this document. See the 'DOOM: Rec.Games.Computer.Doom FAQ' or 'DOOM: FTP and WWW Sites' postings in the* newsgroups for a complete list.

The URL of the directory that contains the Doom FAQ files (usually in TXT format, compressed in a ZIP file) is:

The latest official version of the BFG FAQ is also posted monthly to the and .playing newsgroups. This is part of the RGCD Periodic Information Postings (PIPs). If your news server does not keep the articles long enough for you to find one of the PIPs, they are archived at:

The official location for the hypertext version of the BFG FAQ is DoomGate on the World Wide Web. Check it out here, along with some other good documents:

Section 1 - BFG Basics

1A. What is the BFG9000?

The BFG9000 (or BFG) is arguably the most powerful weapon in the computer games Doom, Doom II, and The Ultimate Doom. It is also the most difficult weapon to use well in a deathmatch (multi-player competition), because it does not behave in a simple 'point and shoot' fashion.

When you have it in your arsenal, the BFG is selected by pressing the 7 key on your keyboard.

When you pull the trigger, there is an excruciatingly long pause as the weapon warms up. Then a large green ball of plasma is emitted from its barrel. The plasma ball flies in the direction you fired it until it hits a target or a wall. Like all weapons in Doom, it will fly straight through decorative objects like torches or trees.

When the green ball hits a solid object, it detonates and does two types of damage: Direct Hit and Blast Area. Each damage type is outlined in its own section, later in the FAQ.

1B. What does 'BFG' mean?

The general consensus is that BFG stands for Big Fragging Gun. Well, that's the G-rated version at least. Hank Leukart's Official Doom FAQ (the one that ships with the game) says so.

So is "Fragging" a deliberate softening of another famous F-word? Maybe. But the term "frag" is an actual word, and it's used in Doom to represent a confirmed kill in a deathmatch game. This comes from the idea that in a deathmatch, you are killing your fellow space marines. The definition of frag is:

    frag Slang. Verb, transitive
    fragged, fragging, frags
       To wound or kill (a fellow soldier) by throwing
       a grenade or similar explosive at the victim.
That's not to say that the the word Frag isn't often interchangeable with the other word. And, of course, the Quake 2 manual calls the new BFG10K the "Big, uh, freakin' gun."

Other good name suggestions that have found their way to the authors are "Big Funny Gun" (Chris Somers) and the much more logical "Blast Field Gun" (William D. Whitaker). I'm sure there are thousands of names you could invent for it...

1C. Where can I find the BFG in the game?

Listing all the locations that the BFG can be found is beyond the scope of this document. For detailed information on the location of all weapons, please consult the other FAQ files. Keep in mind that the BFG appears more often in deathmatch games than it does in single player games.

1D. What is the cheat code for the BFG?

While you are playing the game, type the keys IDKFA to give your marine all weapons, keys, and ammunition. Then press the 7 key to select the BFG.

Note: This cheat code is disabled in multi-player games and single-player nightmare-skill games.

1E. Why is the BFG missing in my version?

If you perform the above cheat correctly, but do not get the BFG, you may be playing the shareware version of Doom. You must purchase the commercial version of Doom from a retailer or id Software before the BFG can glorify your screen.

1F. What's this I hear about the original BFG?

The current version of the BFG is not the way id's designers originally envisioned it. The BFG behaved quite differently in a pre-beta release of Doom.

It worked by shooting multiple streams of different types of plasma and fireballs. Because this required an unusually large number of moving objects, it tended to slow down the game. Therefore, the BFG was redesigned with the invisible blast area that is used today.

Recently, these early Doom versions have been distributed on the internet. You can find screen shots and downloads at:
(Update 8-15-99: This is now a dead link. You're on your own.)

If you want to download the one with the special BFG, get the October 4th, 1993 press-release version.

Section 2 - The Direct Hit

2A. What is a direct hit?

A direct hit happens when the BFG's green plasma ball directly hits a target. The target can be a monster, an exploding barrel, or an opposing player in a multi-player game.

2B. How much damage does a direct hit do?

A direct hit with the BFG causes a random amount of damage between 100 and 800 points, in 100-point increments.

The base damage value for the green ball is 100 points, which gets run through the missile damage randomization routine:

       damage = ((P_Random()%8)+1)*tmthing->info->damage;
Note that the above code results in damage values in 100-point increments, i.e., 600 or 700, but not 666.

A note about skill levels: Testing seems to show that weapons always do the same amount of damage to monsters, but that the player objects can absorb the weapons better at lower skill levels. Therefore, it takes more shots to kill a player at lower skill levels, and fewer shots at higher skill levels. This is why some players prefer to deathmatch at the higher skill levels: The frags are quicker that way.

The Doom public code release bears this out. They perform a right bitshift (a fast way to divide an integer by two) on the damage value as follows::

    player = target->player;
    if (player && gameskill == sk_baby)
        damage >>= 1;        // take half damage in trainer mode
And of course, armor is a factor as well. Depending on the type and the amount of armor worn by a player, some armor will be subtracted in lieu of health.

If your target is lucky enough to survive a direct hit, he is still susceptible to damage from the blast area. This happens sometimes in a deathmatch. Since there is a brief pause between the direct hit and the blast area calculation, your victim may go through several stages of fear and elation in the space of one second:

  1. Victim sees the BFG coming towards him (Uh-oh.)
  2. BFG scores a direct hit (D'oh!)
  3. Victim realizes he has miraculously survived (Woo-Hoo!)
  4. The flash damage kills him a moment later (D'oh!)

2C. What are the limitations of a direct hit?

The direct hit is not limited by the same parameters as the blast area. There is no range limit, and the damage does not decrease with distance.

The hard part is that the BFG's plasma ball travels at a fixed speed, and can be avoided by an alert deathmatch player. The reference number for the BFG ball's speed, as stored in the .EXE file, is 25. For comparison, rockets travel at 20 and plasma gun shots travel at 25.

If it seems like this is too fast, and would not be easy to avoid, remember that the plasma gun fires in a continuous stream. The BFG can only be fired once every few seconds. The BFG's green ball is also very bright and large on the screen. All of those factors make it generally easier to avoid in a deathmatch game.

A direct hit in a deathmatch (against good players) is usually the result of luck, or the result of a player that did not know the BFG ball was coming towards him. See section 4 for details of a trick that can help you achieve the latter scenario.

The direct hit can only damage one target. If there are two targets very close together, the green ball can only hit one of them directly-whichever one it touches first.

Section 3 - The Blast Area

3A. What is the blast area?

After the green plasma ball detonates, and after the damage is calculated and deducted from the target that received the direct hit (if any), the area effect of the BFG is calculated. Targets that fall within a specially defined area will take varying amounts of damage.

Simply put, the blast area is like an imaginary 'cone' or 'fan' of damage traces that briefly extends outward from the attacking player. The cone always points in the direction that the weapon was fired. For instance, if you originally fired the weapon in the northwest direction, the cone will always face northwest, regardless of which direction you're facing at the moment of detonation.

Note that this does not mean that the attacker must continue to face in that direction. The attacker is free to turn away from his targets, as long as he moves to a position that keeps this imaginary cone pointed at them. Common misconceptions are that you must be facing either the targets, the detonation point, or the same direction as the weapon was fired. None of those things are necessary in order to inflict damage.

Also note that this imaginary cone has no relation whatsoever to the detonation point. The location of the detonation point is only important for the direct hit (see section 2). Only the moment of detonation is important, not the location. It is possible to have the green ball detonate twenty miles away in a completely different room at a totally different altitude, but the blast can still cause damage right next to you.

The paragraphs above cover the basic concepts of the blast area. More detailed information can be found in section 3D, below.

3B. How much damage does the blast area do?

Since the Doom public code release, I'm revising this section. Originally, we were told that there were 20 traces, each doing a random amount of damage between 5 and 15 points. But now that I look at the public code release, it's telling me a different story. I've confirmed this with Bernd. The function "A_BFGSpray" is pretty simple, and here's how it works:

There are 40 traces, and each one does 1-8 random points of damage in a 16-iteration loop. Meaning each trace will do between 16 and 128 points of damage.

Because these traces radiate outward from the attacker in a fan shape, a target will more likely be hit by a given trace if he is close to the attacker. Therefore, targets closer to the attacker will generally take more damage because they are hit by more traces.

If a target is very close to the attacker (for instance, standing right next to him), the target might be within the hit range of all the traces. The amount of blast area damage in this situation would be between 640 and 5120 points. However, all traces would not necessarily be absorbed by that target, and might move on to other targets. See section 3F, below, for more information on this phenomenon.

A note about random numbers:

A phenomenon known as the 'bell curve' happens when you combine the outcome of multiple random numbers. Players of book-and-paper role-playing games may recognize it. In those games, you would often use three dice to generate a random statistic. In theory, adding the three dice would generate a random number between 3 and 18. But in reality, the actual results would be weighted towards the middle of the range, around eleven. The odds of getting a three or an eighteen are rare because you'd have to roll 1+1+1 or 6+6+6. There's only one possible combination for each outcome. On the other hand, rolling an eleven is relatively easy: 6+4+1, 5+5+1, 3+3+5, etc. If you were to graph the outcome of a thousand rolls, the graph would be shaped like an arc or a bell, with more rolls coming up in the middle of the range of possible values. Hence the name 'bell curve'. The role-playing games use this to make certain random statistics more fair.

This applies to the damage traces, as well, because they are essentially a group of multiple random numbers. For instance, although the possible damage for a single trace is 16-128, the odds are that the total damage from a trace will more likely be around 50-60 points, due to the bell curve. The odds of doing full or minimum damage in that situation would be extremely rare.

Actually, if you look at the Doom code, you'll find that even the random numbers aren't random. They're "pseudo-random", and for a very good reason: So that all four computers in a multiplayer game can be synchronized. They pull the random numbers from a table whose index changes each time it's accessed. Looking at the table, it's obvious that there are no "runs" of all low or high numbers, so it's not only unlikely that full or minimum damage would be done, it's actually impossible in the current code.

3C. How long does the blast effect last?

The blast effect is instantaneous, but it does not activate until the "S_BFGLAND4" frame plays. This can be seen in the source code in the frame/action pointer table in "info.c".

What this means is that the "A_BFGSpray" function is triggered 16 game tics after the first death frame of the direct hit was started. Assuming a game tic is 35 frames per second, then the blast effect is calculated 0.4571428571429 seconds after the detonation. Which, Captain, if I had any emotions, I'd be excited about.

But what about the other thing?

Oh, you mean, when someone is running out from from behind a corner, and it looks like the blast area should have missed them, but it got them anyway? How can that be? They ran out from behind the corner after the blast area was calculated!

Well, it's been a while (two years) since I LAN-playtested this phenomenon. We were never able to nail it down under controlled tests. The "A_BFGSpray" function calculates completely within a single game tic, and if there's a slow computer in the game, all of the computers will freeze until the slow computer is done with its blast area calculations.

The only thing I can figure is, the guy's radius (which is larger than his visible sprite) was within sight of the damage traces. He took damage while he still seemed to be behind the corner, even though he wasn't. More on this phenomenon below.

3D. How exactly does the blast area work?

The blast area is a spread of invisible traces that radiate outward from the attacking player. The damage for the traces is calculated shortly after the green ball detonates against a target or a wall.

Here's the code for the function in the public code release. I've waited two years to see this:

void A_BFGSpray (mobj_t* mo) 
    int                 i;
    int                 j;
    int                 damage;
    angle_t             an;

    // offset angles from its attack angle
    for (i=0 ; i<40 ; i++)
        an = mo->angle - ANG90/2 + ANG90/40*i;

        // mo->target is the originator (player)
        //  of the missile
        P_AimLineAttack (mo->target, an, 16*64*FRACUNIT);

        if (!linetarget)

        P_SpawnMobj (linetarget->x,
                     linetarget->z + (linetarget->height>>2),
        damage = 0;
        for (j=0;j<15;j++)
            damage += (P_Random()&7) + 1;

        P_DamageMobj (linetarget, mo->target,mo->target, damage);
The traces radiate outward in an imaginary cone that is 90 degrees wide. This is, coincidentally, about the same width as the player's field of view.

Because the code uses "mo->angle" as the source for its angle, the cone always points the same direction that the green ball flew. For instance, if you fire the green ball in the southeast direction, your cone of traces will always radiate towards the southeast.

However, because it uses "mo->target" as the source for its attacks, the traces radiate from where the player is standing, not from the green ball.


Regardless of how much you run and turn between the time you fire and the time the green ball detonates, the traces will always radiate from your location. Think of it like a tank with a gyroscopically stabilized turret: only the cone's origin point moves around with you, not its direction. The cone's direction remains fixed on the same compass heading.

From a technical point of view, the game engine does not actually keep track of the cone while you're running around. That's just the effect it seems to have. It simply uses the green ball's vector as the source angle for the traces, and the player's current position as the source location.

Note that the vector of the green ball's flight is based on what direction you were facing when the ball leaves the barrel of the gun, not when you pulled the trigger.

Here's a diagram of how it works:

(Diagram of damage cone.)

Note that this diagram is foreshortened. The detonation point would have to be quite far away in order for the attacker to be able to run that far. But the principle is the same, regardless of how far the green ball flies: The damage cone is calculated after the green ball detonates.

When the green ball detonates, the traces are calculated one at a time, using the same criteria for calculation that the engine might use for a bullet: If there is a solid object (a wall, etc.) between the target and the attacker, the trace is harmlessly absorbed by the object. With one exception: In order to hit a target with a bullet, you had to be facing the target. You don't have to be facing your target in order to do damage with one of the traces.

Quick review:

3E. What are the limitations of the blast area?

Revision time. It seems as though there is a hard limit on the range. Bernd says he thinks this line:

        P_AimLineAttack (mo->target, an, 16*64*FRACUNIT);
actually limits the traces to within 1024 (16*64) game units. It's been a while since I playtested this, so I don't remember if I was ever able to register a hit when outside of this range.

Whether it actually limits the range or not, outside that range it would become increasingly hard to get a single trace to land on a given target anyway. So just deathmatch under the assumption that you can't hit anyone outside 1000 units.

If you are unfamiliar with the Doom engine's units, remember that a standard teleporter pad is 64 units across. Line up 16 of those and you've got a basic idea of what 1024 units is.

The blast damage is also limited to targets that have an unblocked line of sight to the attacking player. This does not mean the attacker must face the target. It means that the attacker must be in a position where his traces can see the target, i.e., he could see the target if he were facing in that direction.

3F. How many targets can it hit?

The blast area can only hit as many targets as its traces can touch. Originally, we stated that one trace can damage more than one target. This was because we did tests where a single shot killed 25 imps. But that was back when we thought there were only 20 traces. Now that we know there's 40 traces, it seems as though the number of objects that can possibly take damage is 40.

Of course, in regular game play, rarely are that many targets standing in such a perfectly aligned pattern. Usually, some individual targets will soak up more than one trace, while other traces miss targets completely.

The traces are calculated on a 'first come, first fragged' basis. For each trace, the damage is calculated and subtracted from the target, and the target dies if there's enough damage. Then the engine moves on to the next trace.

Here is how it works:

(Please note: In the discussion below, we refer to 'line of sight' loosely. Remember that the attacker does not need to be facing his targets to inflict damage.)

In the following scenario, imagine that the attacker is standing in a direct line with several targets (imps, perhaps) lined up in front of him, and the green ball detonates on a wall somewhere:

(Picture of attacker standing in front of a row of imps.)

The first couple of imps are close to the attacker. They crumble, having soaked up some of the traces that are pointing ahead of the attacker. The next few imps are a little further away, and absorb some more of the traces, but not as many. They absorb fewer traces for two reasons:
  1. because the imps in front of them absorbed some of them already, and
  2. because they are further away and the traces are more spread out.
But they still die. The next imp gets damaged, but does not die. He has soaked up the last trace that was headed in that general direction. The last imp is not damaged at all because there are no more traces left in his direction.

In order for the above scenario to work, the targets must be perfectly aligned. For instance, in the following scenario, all of the targets take full damage, because there's no one in front of them to soak up traces.

(Picture of attacker standing in front of some scattered imps.)

The one target in the back (Y) is still susceptible because it is not blocked by another target. The attacker can see him through the gap. So, for example, an imp standing directly behind a cyberdemon is fairly safe, but an imp standing next to a cyberdemon is a sitting duck.

The moral to this story is: In deathmatch, do not depend upon other players or monsters to absorb the BFG blast unless they are exactly between you and your attacker. And you'd better hope they're very healthy. In all other cases you take full damage.

3G. How does altitude affect it?

For the most part, it does not. With a few exceptions.

Again, in the discussions that follow, we refer to 'line of sight' loosely. You do not have to face your targets to hit them.

If a difference in altitude brings your target out of the sight of your traces, then yes, it makes him safe from the blast damage. But if your traces can see any part of him, he takes full damage regardless of how much higher or lower you are than he is.

As far as altitude is concerned, the traces seem to use the same criteria as your view does to determine if the target is visible. In other words, if both you and the damage cone are facing the target, but the target is above the top of the screen, you can't hit him.

But there is a catch. The upper and lower angle limit of the traces seems to be the same as your view would be if your screen was fully zoomed in. For instance, if you are displaying the status bar at the bottom of the screen, your view window is slightly cut off at the top and bottom. Press the plus (+) key repeatedly to zoom all the way in, and you can see what this means. The BFG's traces seem to use the same angle as this full view does to determine if they can hit the target. So if you've got the status bar showing, you can actually hit someone who is off the top of your screen. If you are fully zoomed in, your view seems to be an accurate representation of the damage cone's angle.

Note: The angle limit of the traces is not affected by changing your zoom level. The traces use the same angle regardless of what your zoom is. It's just that zooming all the way in changes your screen's aspect ratio. So you can see more stuff at the top and bottom of the screen, stuff that normally would have been hidden behind the status bar.

If you are standing on a ledge above your target, and you are so close that you can 'touch' him (i.e., you can't step off the ledge because you're bumping into him), your shots will go right over his head and the blast damage will not affect him. This is because, technically, the traces can't see him. Well, if you could look down you would see him, but you can't look down in Doom. Must be those darned restrictive space helmets.

3H. If I am only partially exposed, do I only take partial damage?

No such luck. The only thing that reduces your damage is getting hit with fewer traces. Here is how it works:

If you are hiding behind a decorative sprite (such as a tree or a technical column) you are fully exposed. All weapons in Doom always pass completely through decorative sprites.

If you are peeking over a podium, or partially obscured by a raising lift, or a closing door, and only half or one-tenth of you is showing, you still take the full amount of damage. The traces are calculated based on the game's two-dimensional block map. As far as the game engine is concerned, all of the traces can still hit you.

If you are hiding behind a vertical wall with your rear end peeking out, I'm pretty sure you still take full damage because the traces auto-aim at you. Tests seem to show that your distance from the attacker is more important than how much of you is exposed.

Also remember that what counts as 'showing' may not be what you think. The Doom engine uses the radius of the player to determine visibility. Your player's aspect ratio does not change when you rotate. It also seems as though your radius is slightly larger (in some cases) than the sprite (picture) that represents your player. In tests, it is possible to inflict damage upon a player that seems to be out of sight (no visible pixels) but whose radius is large enough to count as 'visible' to the BFG traces.

3I. What happens if the attacker is fragged before detonation?

The BFG's traces are still active, even if the attacking player is dead. So if you fire the BFG, then get fragged, do not press the space bar to respawn your marine right away. Wait until the green ball has detonated before you respawn.

Here's why:

Even after being fragged, you can still see the action from your fixed point of view on the ground (your 'dead' state). The traces remain active and can still frag an opposing player (hopefully the one that fragged you). The traces will radiate from your dead body's 'eyes'. The traces still follow the same rules, i.e., they radiate in the direction the green ball was fired, regardless of which direction your 'dead view' is facing.

In a previous version of this FAQ, we reported that you will lose the chance to frag your opponent if you respawn before detonation. Several people pointed out to the authors that the statement was in error. The traces remain active even after respawning. Testing shows that the traces do, in fact, continue to radiate from the dead body even after you have respawned in a completely different area of the map. This testing was performed at the prompting of Kirby Nixon, who insisted that it was true. Whaddya know? He was right.

This means that, technically, you don't need to hang around and watch your opponent in order for the traces to work. But Kirby pointed out a good reason to wait for the detonation before respawning: Your dead body's traces can frag you, too! Just because they were once your traces doesn't mean you're immune. If you are unlucky enough to respawn within your dead body's damage cone, you can kiss your butt goodbye.

Of course, the same thing applies to projectile weapons like the rockets and plasma. If you play enough deathmatch, you've probably been fragged by your own rocket a few times. Don't be embarrassed, it happens to the best of us...

Please note: Any projectile kills made by a respawned player (whether by rockets, plasma, BFG traces, etc.) do not contribute to that player's frag count. Killing yourself in this manner does not change your frag count, either. This appears to be because the game engine creates a new instance of the player-object at respawn-time, and therefore 'forgets' to award that frag. In any case, if you wait before respawning, you will get credit for the frag as long as you're still dead. This is another reason to wait for detonation before respawning. Special thanks to John Castelli for pointing this one out.

3J. What about multiple BFG shots?

Each BFG shot is tracked and calculated independently. The game engine's code is object-oriented, and has no trouble keeping track of multiple blast areas. Each damage cone's direction is based on the direction of its corresponding green ball.

The origin point of the damage cone is based on the current location of the marine who fired it (even if that marine is just a dead body- see section 3I for more info).

Section 4 - Deathmatch Techniques

4A. What is considered unfair when using the BFG?

Many deathmatch players moan and groan when the BFG is used successfully against them. 'What a cheap frag, you craven coward!' they shout. Well, they usually use fewer words to express the idea, but that's what they mean. This is usually due to a lack of understanding about how the weapon works.

The purpose of this FAQ is to educate players about how the BFG behaves. If you know how it works, you will know how to defend yourself against it. You will also know how to effectively attack with it. If both (or all four) players have the same knowledge about how the weapon functions, then the BFG by definition is not unfair. If you play against an opponent who does not know how the BFG works, then you should make sure to educate them on its behavior before turning them into paste.

Having said that, the following things are debatable regarding fairness. I'm not saying they are patently unfair, I'm just saying that their fairness is debatable:

In the last two examples, four-player deathmatch tends to cancel out any advantages to those techniques. The remaining three players usually coordinate and attempt to bring down the king of the hill in these situations.

4B. What is the best way to defend against the BFG in a deathmatch?


(OK, so it ain't Rocket Science.)

This requires, of course, that you know where the cone of damage actually is. That, in turn, requires that you know where your attacker is and in what direction he fired the weapon. That, in turn, requires that you know the weapon was even fired at all. Which, in turn, may be difficult against a player who has mastered the Silent BFG trick (See section 4D).

It still helps if you are playing the game with a stereo sound card and headphones. This allows you to hear how far away and in which direction your opponents are. If you think in three dimensions, the sounds you hear in the game will give you a great tactical advantage.

You must understand completely how the weapon works before any avoidance technique would be meaningful. So if you skipped ahead to this section, go back and read the gory details.

With all that said, here are a few ideas. These are just things to try, not necessarily good things in all cases.

4C. What is the best way to attack with the BFG in a deathmatch?


(You were expecting some deep revelation, or what?)

This requires, of course, that you know where the cone of damage actually is. So if you looked here first, go back and check out the rest of this FAQ for details.

Anyway, here's some ideas. Not necessarily comprehensive:

4D. What is the Silent BFG trick?

Defending yourself against the BFG pretty much depends on your ability to know precisely when it is being used against you.

If you are fortunate enough to play deathmatch with a stereo sound card and headphones, you know that sound cues are vital to playing well in deathmatch. In many cases, the only way a potential victim knows the green ball is in the air is by the distinctive sound the weapon makes when fired. The headphones can give him directional cues as to its origin, and therefore point the way towards a proper escape.

So if you wish to get the drop on someone, wouldn't it be great if you could put a silencer on that weapon? Well you can. A limitation in Doom's sound code allows you to silence the firing sound of the BFG. Regardless of the 'Number of Sound FX to Mix' that you chose in Doom's setup program, your character can actually only utter one sound at a time. This includes all weapons firing. If you cause your character to grunt, i.e., you jump off of a ledge or press the space bar on a blank wall, you have a brief period while the grunting sound is being played in which you can pull the trigger and no sound will be emitted from the weapon. Your grunt makes a little noise, but it's relatively quiet and is sometimes ignored by your opponents.

I've seen other information that tells me I've got it backwards: That you're supposed to fire first, then grunt. I don't know which is correct. Try both and use whichever one works for you.

While it works well in theory, in practice the trick is hard to perform. It also may be a little unfair. As with all secrets, it definitely makes the game unfair if you don't share this information with your opponents.

As of this writing, there seems to be a small handful of players on the doom newsgroups who use this trick. The first person to submit this trick to the author of this document was John Fedor.

Interesting anecdote: When reviewing a draft copy of this FAQ, American McGee at id Software informed us that they have been using the Silent BFG trick in their deathmatch games since day one.

4E. What is the Level One Strafe trick?

The level one strafe trick is not a deathmatch technique per se, but it's a demonstration of the BFG behavior that educates many folks on how the BFG really works. The act of performing this trick tends to open one's eyes to the amazing possibilities of the weapon. It also proves some points made in this FAQ.

Doug Bora first pointed this demo out to our particular group. Credit for the original version of this demo goes to John Ripley of the UK. The full deathmatch demo file PETALK2.ZIP is the first example of this specific action. Since that time, this has been repeated by many folks on the Doom newsgroups.

PETALK2.ZIP should be available at:

ftp://{INS site}/lmps/doom2/1.9/

where {INS site} = any DOOM ftp site, eg.

Click here to attempt to download the file from now.

(If the link above does not work, please consult the other FAQ files for information on FTP sites that carry doom-related files. The author won't be updating this particular link if it changes.)

How to do this:

This demonstration proves the following: Players who perform this stunt successfully the first time are usually amazed that it actually works. This is also a good practice for using similar moves in real deathmatches.

Section 5 - Submitting Corrections

5A. Common misconceptions

This is a list of the most common misunderstandings about the behavior of the BFG. Please review this list before submitting corrections.
  1. You have to be looking at your target in order to inflict blast area damage.

    This is untrue. The target must be within an imaginary line-of-sight to you at detonation time, but you can be facing away from the target, provided it meets all the other criteria.

    This is an easy mistake to make because you tend to be more accurate in positioning your cone of damage if you keep your eyes on your targets. Especially if you are strafing instead of rotating.

    See section 4E for proof of this.

  2. You have to see the detonation point in order to inflict blast area damage.

    Nope. The detonation point can be completely out of your range of sight, and can be separated from you and your targets by a hundred solid stone walls.

    Again, see section 4E for proof of this.

  3. The location of the detonation point is a factor in the blast damage area calculations.

    Only the moment of detonation is important. The location of the detonation point is not used. See number 2, above.

  4. The location you were standing when you fired, or the location of targets at firing time, is a factor.

    Only the location where you are standing when the blast detonates is important. The compass direction that you fired is important, but not the location where you fired. The traces are only calculated at detonation time. The game engine does not care where the targets are until the traces are calculated.

    Again, see section 4E for proof of this.

  5. You have to be facing the same direction at detonation time as you were at firing time.

    No, the cone of traces extends outward in the same compass direction regardless of which way you are facing at detonation time.

    Again, an easy mistake to make because you tend to be more accurate if you keep your eyes on your targets. Again, especially if you are strafing.

    Again, see section 4E for proof of this.

  6. Your BFG blast can frag someone behind you, but only if they are close enough to touch you.

    You can frag someone behind you if they fall anywhere within the cone of traces. Sure they can be behind you, but they don't have to be touching you. In order to frag someone behind you, you must rotate away from the direction you fired, then maneuver so that your targets are within the cone behind you.

    Having said that, if the victim is standing right next to the attacker, at 90 degrees perpendicular to the cone of damage, they will fall within the cone if they are in front of the attacker's centerline. But if they are truly behind the attacker's cone of damage (behind the centerline of the attacker), they will walk away unscathed.

    This seems to be due to the fact that the player's 'hittable' radius is larger than the player's 'walk into' radius. When you walk up to a player and bump into him, his 'hittable' area is overlapping into your area.

    This is an easy mistake to make when looking at a deathmatch game, where everyone is moving around each other so quickly that it's hard to keep track of the location of the cone of damage. If you really think you fragged someone behind you, it's probably because of one of two reasons:

    1. They were actually next to you and slightly forward of your centerline.
    2. You rotated away from the direction of fire, and the victim stepped into the cone of damage that still existed behind you.

5B. I think the FAQ is in error. How do I get it corrected?

Please go through this checklist before submitting information:
  1. Read the entire FAQ to be sure we did not cover your point in another section. Check the 'Common Misconceptions' section, above, too.

  2. If you have a theory about the BFG behavior, please test it carefully before submitting it. If you can't reproduce the effect under controlled conditions, you were probably witnessing a side effect of one of its known behaviors. Or perhaps it happened in a deathmatch game, where the action is so fast that you often can't keep track of what's going on.

  3. If you think you have tested your theory thoroughly and are ready to submit the theory as proven, please prepare a short, precise description statement that details how to reproduce the effect during game play. Demo recordings are not necessary.

  4. When you have composed your message, e-mail it to

  5. Note: Do not attempt to send us information for FAQ files other than this one. We do not maintain other FAQ files and we do not echo information amongst other FAQ authors.

Appendix A - Quake Mods

Quake 1 BFG Mods

The ability to make user-created code modifications to the Quake engine was one of Quake's most important features. These modifications, called "patches" or "mods" number perhaps in the thousands. Some of the patch authors decided that Quake deserved a BFG, too. Here's a short list of some of the Quake BFG patches I've run across in my travels.

Since Quake's code is totally different than Doom's code, these BFG remakes can't be precisely like the original BFG. Most of them get pretty close in terms of "feel", though. The biggest difference is that they all have a "Z" direction for their damage cone, i.e., they can be aimed upwards.

Note that this list is not comprehensive and isn't necessarily up to date.

Deathmatch Plus

(Update 8-15-99: This is now a dead link. You're on your own.)
Author: William Harris
Comments: This patch includes other interesting weapons such as the Cluster Bomb. This patch was specifically designed for deathmatch play.

The BFG 9500

(Update 8-15-99: This is now a dead link. You're on your own.)
Author: Nelno the Amoeba
Comments: Designed for single player.

Doom 2 Total Conversion

(Update 8-15-99: This is now a dead link. You're on your own.)
Author: Andy Bay
Comments: A Total Conversion project for Quake, allowing you to play Doom 2 with the Quake engine.

Your Path of Destruction

Author: Curtis Moxley
Comments: A Doom Total Conversion project for Quake, including another original piece of QuakeC code for the BFG.


(Update 8-15-99: This is now a dead link. You're on your own.)
Author: Luke Whiteside (WeAsL)
Comments: A set of QuakeC modifications for deathmatch play, with several new weapons including a variation on the BFG.


Author: Requiem
Comments: A Conversion for single player and multi player Quake, with extra attention given to making a balanced set of weapons. Includes the good-old BFG.

Appendix B - Quake 2

The Quake 2 BFG10K

Pandora opened the box again! They put a BFG in Quake 2! It's different from the Doom BFG, and different from the Quake 1 BFG mods.

Randy Pitchford of Gearbox Software has written up an excellent Quake 2 Weapons FAQ. This document can be found at:

Randy and I have corresponded, and between his team's research and a few peeks at the Quake 2 public code release, we've got the BFG10K's behavior pretty much figured out. I'm only going to review it briefly here, and you can go look at Randy's FAQ for all the details. So, in other words, the torch has been passed.

Briefly, the main differences between the Quake 2 BFG and the Doom BFG are:

  1. If you detonate it against a wall or floor next to you, there's a small rocket-style blast radius at the detonation point. It can hurt you. This is to keep you from using your old Doom BFG tricks. But it can also allow you to BFG jump, similar to rocket jumping.

  2. The green ball shoots green lasers at targets as it flies along.

  3. The direct hit is more powerful.

  4. The area damage (called the "BFG Effect" in the source code) isn't done with 40 damage traces. Instead, you must triangulate lines-of-sight between the target, the detonation point, and the attacker. In other words, to take damage, the target must be within an imaginary line-of-sight to both the attacker and the ball.

  5. The BFG Effect has a hard-coded 1000-unit range limit, similar to Doom. But the range is measured from the detonation point instead of from the attacker. (The way it should be!)

  6. The BFG Effect damage amount is up to 500 points per target, with an inverse square falloff between the detonation point and the 1000-unit limit. Here is the code line:

         points = self->radius_dmg * (1.0 - sqrt(dist/self->dmg_radius));
    So the farther away the target is from the detonation point, the less damage the target will take.

In my experiences, the best way to attack with the BFG10K is similar to the Doom way: Get a target in sight, then quickly detonate the green ball on a wall, ceiling, or floor next to you. The only twist is that you need to keep out of the way of the local blast radius. You also need to make sure that the ball is detonated is a place that's got a clear line-of-sight to the target. For example, shooting the back side of a column, unlike Doom, is useless in Quake 2.

The best way to defend against the BFG10K is to hide and/or run from the ball. It keeps you out of the way of the lasers, as well as keeping you out of the way of the BFG effect.

That's about all I need to say about the BFG10K (hey, that rhymes). Check out Randy's FAQ for the rest. See you on the Quake 2 servers! I'll be the one gathering cells for my BFG...

THE END. Thanks for reading the BFG FAQ!