• Weapon Class: Special, Explosive Energy Projectile

• Ammunition Type:

Cells

• Ammunition Expended Per Discharge: 50 Cells

• Rate Of Fire: About one shot per 2 seconds

• Most Effective Range: See Below

Best Strategy:  See Below

The BFG is the most complex weapon in Quake2.  It has four different types of effects that all happen within a few moments of each other every time it is fired.  I’ll quickly describe those effects here, and delve into the weapon in greater detail below.
But first know that only one of the BFG damage effects are increased with the Quad Damage power-up: the Detonation Blast Effect.
Impact Effect

Laser Effect

Radius Effect

Detonation Blast Effect

BFG Effect Example and Explanation
What if the shooter dies before impact?
Do you have to be looking at a target to hurt it with the blast?
What’s the best way to defend against the BFG10k?
Do you have any special tricks with the BFG offensively?
BFG Jumping

Impact:   The most obvious effect is the impact effect.  If the green ball hits a target, the target will most likely perish. This damage effect also carries with it a radius blast that is twice as damaging to the shooter as it is to the target.
Lasers:

The next most obvious effect are the laser beams that burn out from the green ball as it flies through the air.  While the green BFG ball flies towards it’s target, it will actively seek nearby enemies and cook them with a green laser beam that is drawn from the ball to the target.  That beam does 50 points of damage per second in 5 point increments.

The beams will only burn targets within 256 game units from the green ball.  256 units is about 20-25 feet.
Radius Effect:

A large radius damage effect occurs very close to the detonation point of the green ball.  This is there to keep you from firing the weapon directly into a wall or floor.

In the source code it dictates that the shooter of the BFG will take twice as much damage from the blast radius effect as any other target would.  It seems that the designers wanted to punish a BFG shooter who fires the weapon to impact at close
range.  It’s a good design decision as the greatest damage that can result from the BFG 10k is from the detonation effect.
Detonation Blast Effect:

This is the serious damage from the weapon.  It’s somewhat difficult to understand, but later I’ll provide some examples of how to test the weapon’s effect yourself to fully understand its inner workings.

The basic concept is triangulation.  In order for a target to receive the detonation blast effect (up to 500 points of damage in single play, 200 in deathmatch) a line of sight must be able to be drawn from the target to the BFG detonation point and from the target to the player that fired the BFG at the moment of detonation.  If any solid level geometry blocks such a line of sight from either object, the target will take no detonation blast damage.

It does not matter what direction the player or the target is facing, and the shooter does not need to be able to see the detonation point.  In fact, the shooter doesn’t even have to be actually looking at the target.  As long as a line of sight can be drawn, it’ll cause the damage.

Blast damage total is exponentially related to the targets distance from the detonation point.  The farther a target is from the BFG impact point, the less damage will be sustained.

Furthermore, relative position only matters for calculating total blast damage, not whether damage will be inflicted..  An opponent who stands behind me as I fire the BFG away from both of us towards a distant wall will be sufficiently cooked from the detonation blast if neither player moves before detonation.
Example to help understand the effect of the BFG:

   In the above example assume the shooter is firing the BFG to the right while the target is behind the shooter all along. When the shot is first fired, the target will likely get hit with some laser beam damage.  As the ball flies towards the end of the corridor, the beam will be out of range and stop causing damage When the BFG detonates, as long as no obstructions block the shooter’s or the blast’s line of sight to the target, that target will get cooked with the detonation effect and probably die.   Also note that all of this assumes that the target is within 1000 game units of the detonation.

What if the shooter dies before detonation?

As with the BFG in DooM and DooM][, a dead BFG shooter will kill any legal targets as long as line of sight isn’t broken. It is possible to fire the BFG, die and remorph within sight of the BFG detonation point and your old dead body. In that case
you will have killed yourself as your new body will get pasted by the detonation blast effect.

Do you have to be looking at a target to hurt it with the blast?

Nope, as long as a Line of Sight line can be drawn between from the player and the impact point to the target, that guy is toast.

What’s the best way to defend against the BFG10k?

For each of the different effects, there’s a different strategy that helps to avoid damage.  First, you should attempt to avoid getting hit with the actual green BFG ball.
Then, you should determine where the green ball is going to detonate and make sure you’re not in direct line of sight to that point when it explodes.  Since your opponent will
most likely be attempting to keep you within his/her own line of sight, your best bet is to worry about the ball itself.  Once the ball is fired, it’s path is predictable. Lastly, if at all possible, you should try to keep enough distance from the ball as it flies to avoid getting cooked by it’s lasers.  If you know you’re going to take some laser damage you’re better off charging in the opposite direction the ball is flying in as opposed to trying to out run it in the same direction it’s travelling. Once you completely understand how the BFG orks it’s much easier to avoid than you expect.  BFG wars with an opponent who also understands the weapon is one of the most exciting and enjoyable parts of Quake2 deathmatch.

Do you have any special tricks with the BFG offensively?

Yes.  Try this:  Instead of firing the BFG towards your opponent, do a quick 180 degree mouse flick and and blast it into the floor behind where you were originally facing.  If you continue to use your movement keys to drive you in the direction you were originally heading, you probably won’t take any radius damage from floor impact and the transaction will occur so quickly that your target won’t have time to get clear of
line of sights before the detonation.  It gets ’em every time.

Another trick suggested DarkLegacy[TB] of Clan Thunderbunny is to fire the weapon directly into the ceiling of an open room that contains a target or two. The result, of course, is that any target with a line of sight to you (as the shooter) will most likely also be exposed to the BFG impact point on the ceiling and thus be cooked.

In general, however, it seems the best strategy with the BFG 10k (As Tony Fabris, author of the Doom BFG FAQ suggested) is similar to that of the old BFG.  Detonate it
as quickly as possible after aquiring a target.

BFG Jumping:

It is possible to use the BFG’s blast radius to perform a “BFG jump”.  Like “rocket jumping” the technique involves using the imparted velocity of the weapon’s explosion combined with a jump to boost yourself higher into the air than possible with an regular jump. the technique is best performed by firing the BFG directly into the ground below your feet an instant after the jump button is pressed.  Using a BFG jump will give you a slightly higher jump than with a rocket jump.