The plasma gun (also known as the plasma rifle in the game manuals, help screen and code comments) is a futuristic weapon with a segmented barrel, which fires blue and white bursts of plasma. It shares the player's stock of energy cells with the BFG9000 as a source of ammo.
The plasma gun first appears in a secret area of the very first level of the second episode, E2M1: Deimos Anomaly, and happens to appear in every level of The Shores of Hell, with the exception of the Tower of Babel level. It first appears in a non-secret area in the fifth level, E2M5: Command Center. When picked up, it contains the equivalent ammo of 2 cells (totalling 40 units of energy, or 80 on the "I'm too young to die" and "Nightmare!" skill levels).
Each plasma burst inflicts 5-40 points of damage. Although the rate of continuous fire is one burst every 3 tics (about 0.086 seconds), there is a further pause of 21 tics (0.6 seconds) when the trigger is released.
In Doom 64, the plasma gun sprites are completely redrawn. It has a blue electric tube on top, which makes a constant buzzing sound. Like the shotguns, the recoiling animation is non-existent, likely to save cartridge space.
The main difference is that it fires at a slower rate of one projectile every 4 tics. Because the game runs at 30 tics per second instead of 35, this translates to one projectile every 0.133 seconds. If the trigger is released, there is no cooldown pause and the weapon is immediately ready to fire again. The amount of damage the projectiles do is unchanged, but they have a faster travel speed of 40 units per tic.
Due to its high damage rate (three times that of the chaingun), the plasma gun is devastating against nearly any single opponent. A continuous barrage will stop an arachnotron, mancubus or revenant dead in its tracks, and even reduce a baron of Hell to about half its normal movement speed and attack frequency. Attacking monsters from long ranges can be inefficient, however, as enemies tend to move too much for the bursts to be accurate; it is also difficult to use against flying monsters in open areas, as the first few hits push the enemy rapidly backward and often to one side of the stream. A good tactic to counter this weakness is to fire the plasma gun in controlled bursts, as opposed to fully automatic fire. Otherwise, it is a very powerful weapon that can be considered the game's jack-of-all trades.
Although the plasma gun does not inflict blast damage, firing it in close quarters demands a certain amount of concentration owing to horizontal auto-aim, which may steer its projectiles right into a wall if the nearest monster is not directly in front of the player. For example, using the plasma gun on the cyberdemon in E4M2: Perfect Hatred, without placing the player in its line of sight, requires aiming at a point slightly to the monster's left.
- In the Doom press release beta, the plasma gun fires green-white and orange-red bursts, alternating between the two colors. This is similar to that version's BFG9000, which fires 40 of the same projectiles per shot. For the release of Doom, these plasma bursts were made blue-white, and the gun sprite was changed slightly.
- Like the shotgun, the plasma gun was created from an existing toy gun, a dart-shooting M60-like toy that was popular in the early 1990s (the version of the toy produced at that time was tan). The area in front of the bipod could be detached to use as a separate weapon. The designers simply turned the detachment around so that it was shown backwards. The resemblance is most apparent when the player lifts the weapon at the end of a volley.
- The rapid fire of the plasma gun often requires many sprites to be rendered simultaneously. This has been known to cause lag during multiplayer games or on older machines (see also the notes on the early BFG).
- The plasma gun can gib zombiemen and sergeants due to their rather low health (20 and 30 hit points respectively).
- The plasma gun is apparently the best all-purpose weapon in the game according to the source code, since the automatic weapon switching when out of ammo (in P_CheckAmmo in P_PSPR.C) uses the order plasma gun > super shotgun > chaingun > shotgun > pistol > chainsaw > rocket launcher > BFG9000 > fist. The rocket launcher and BFG have low priority because of their heavily specialized roles which can make them undesirable in many situations. As a result of the priority settings, the player will switch automatically to the plasma gun if he attempts to fire the BFG without enough cell ammunition (40 shots), while this does not occur between the super shotgun and the shotgun.
|Plasma gun data|
|Included ammo||40 (80 on skill 1 & 5)|
|Max ammo||300 (600 with backpack)|
|Ammo type||Energy cells|
|Velocity||25 map units per tic|
(875 map units per second)
|Shots per minute||700.0|
|Appears in||Registered Doom|
The Ultimate Doom
Doom II/Final Doom
|Thing type||2004 (decimal), 7D4 (hex)|
|Sprite||PLAS (before pickup)|
PLSS (plasma burst)
|Shots needed to kill1||Mean|| Standard
|Heavy weapon dude||3.64||0.98||2||6|
|Baron of Hell||45.09||2.84||39||51|
- This table assumes that all calls to P_Random for damage, pain chance, impact animations, backfire checks, and muzzle lighting are consecutive. In real play, this is never the case: counterattacks and AI pathfinding must be handled, and of course the map may contain additional moving monsters and other randomized phenomena (such as flickering lights). It is also assumed that all projectiles are launched at nearly the same range, so that the various procedures call P_Random in the same sequence each time. Any resulting errors are probably toward the single-shot average, as they introduce noise into the correlation between the indices of "consecutive" calls.
- Assumes that direct hits are possible, which does not occur in any stock map.
The IWADs contain the following numbers of plasma guns per skill level:
Appearances in other id Software games
- The Hyper Blaster in Quake II is an analogous weapon to the plasma gun, being a rapid-fire energy weapon that uses energy cells as ammo, sharing its ammo pool with the game's own BFG 10K.
- The plasma gun appears as a redesigned version in Quake III Arena. The Quake III plasma gun has a more streamlined, futuristic look with glowing plasma visible behind transparent parts. The plasma projectiles travel at a higher velocity and create a small radius of splash damage upon impact.
- Doom Eternal's plasma rifle is bears a design strikingly similar to the original game's plasma gun.