A partial invisibility powerup (called blur sphere in the manuals) is a powerup that is first introduced in E1M3: Toxin Refinery from the Knee-Deep in the Dead episode of Doom. In that game and in Doom II it appears as a floating red and blue orb with a pulsing eye-like pattern, whereas in Doom 64 it is purely red with a fast-moving electric pattern.
Picking up this powerup will grant the player partial invisibility for 60 seconds. The player's sprite (in multiplayer mode) will appear similar to that of the spectre, while the affected player will see their own weapons and hands as partially invisible. When five seconds remain, the weapon will begin blinking, signaling the end of the artifact's effects; the player sprite however remains fully blurred until all 60 seconds elapse. Picking up another partial invisibility item while a previously collected one is still active resets the duration to 60 seconds; any surplus time is lost. For this reason it is best to not collect another sphere until the current one is about to expire.
Monsters firing upon an affected player will have their accuracy reduced, in that their aim is horizontally offset by a random angle, causing them to miss more often. Missile attacks receive a random offset of ±22.5°, while the random offset received by hitscan attacks is ±45°. Note than the hitscan attacks of monsters already have a built-in spread of ±22.5°, which means that those attacks aimed at partially invisible player get scattered up to ±67.5° in a random direction on the horizontal plane. This however may cause more experienced players to inadvertently dodge toward incoming projectiles, being accustomed to monsters firing directly forward. Nevertheless, a blur sphere confers a definite advantage against long-range hitscan attacks such as those of zombies or spiderdemons. The partial invisibility is unable to disrupt monster melee attacks, homing missiles, or the arch-vile's flame attack.
Partial invisibility can also be invoked with the cheat code idbeholdi.
This item is included in the items percentage displayed at the end of each level.
|Partial invisibility data|
|Thing type||2024 (decimal), 7E8 (hex)|
|Appears in||Shareware Doom|
The Ultimate Doom
Doom II/Final Doom
The IWADs contain the following numbers of partial invisibilities per skill level:
Other games and ports
Due to difficulty in rendering the effect, all partial invisibility spheres were removed from the Atari Jaguar map set, and all other ports using its map set do not contain any instances of this powerup in those maps. Most were replaced with soul spheres.
The Sony PlayStation version restored the powerup to its vanilla appearance but, as with spectres, it applies translucency to the player's sprite and weapons. However, it was not added back to maps which were adapted from the Jaguar version. In the Ultimate Doom episode, the powerup only occurs in levels beginning with MAP26: Sever the Wicked. It appears as normal throughout the Doom II episode. It can also be found as usual in all episodes of the PlayStation Final Doom.
The Sega Saturn version retains the powerup and effect from the PlayStation version, but re-implements it using a stipple pattern due to the system's lack of hardware blending support. When displayed on a typical 1997-era CRT television set with an analog input signal, this effect was largely indistinguishable from actual translucency.
The Super NES version of Doom retains the powerup for players, but like the PlayStation version applies translucency using the Super Nintendo PPU's hardware layer blending capability. At the same time however, it does not retain spectres as enemies, since they cannot be drawn on a separate layer in the same way as a player's weapon, and the Super FX blitter's capabilities do not include the ability to blend individual elements of the screen against an existing background within the same layer. The Super Nintendo version makes the powerup more powerful: unawakened enemies will not see the player at all unless approached at melee range or if they take damage from an attack.
Doom 64's partial invisibility item has the appearance of a dark red sphere with a central core emitting multiple electric arcs. Like the PlayStation version, the marine will appear slightly translucent.
The partial invisibilty powerup, as seen in the Doom press release beta.
Reworked effect seen on the player's weapon sprite in Sega Saturn port.
- Demons and spectres appear to direct some attacks away from an invisible player, but only the sprite frames have been changed; the melee attack is aimed normally. In versions of Doom prior to v1.5, the attack angle was also offset, and consequently these monsters could initiate infighting.
- When an invisible player is killed, his corpse sprite will retain its blurry appearance, as a spectre's corpse does.
- Deathmatch players should note that weapons with visible projectiles, particularly the plasma gun, can give away a blurred player's position, as the opponent may target the shots' point of origin.
- ZDoom-based source ports enhance the powerup's effect so that, in addition to the above, idle monsters are not alerted when the partially invisible player is within their sight, as with the similar Shadowsphere powerup in Heretic.
|Items from Doom, Doom II and Doom 64|
|Health:||Health bonus • Stimpack • Medikit|
|Armor:||Armor bonus • Armor • Megaarmor|
|Powerups:||Berserk • Computer area map • Invulnerability • Light amplification visor • Megasphere • Partial invisibility • Radiation shielding suit • Supercharge|
|Keys:||Keycard • Skull key • Demon Key|
|Weapons:||Fist • Chainsaw • Pistol • Shotgun • Super shotgun • Chaingun • Rocket launcher • Plasma gun • BFG9000 • Unmaker|
|Ammo:||Backpack • Clip • 4 shotgun shells • Rocket • Energy cell • Box of bullets • Box of shotgun shells • Box of rockets • Energy cell pack|