E2M3: Refinery (Doom)

E2M3: Refinery is the third map of The Shores of Hell in Doom. It was designed by Tom Hall and Sandy Petersen, and uses the music track "Intermission from DOOM". The par time is 1:30.

On the SNES version of Doom, this level contains the secret exit leading to E2M9: Fortress of Mystery.

Essentials
You begin facing a cage (A) which contains one or more cacodemons. Go behind the cage to see two passages leaving the room to the south, and enter the right-hand passage. You will arrive at a nukage room with two rows of tan partitions, beyond which is a shotgun on a round pedestal with scrolling sides (B). Run straight through to the shotgun.

Turn right (west) into a green marble hall. Take the right and then the left to come to a metal UAC door. Behind this door is the blue keycard (C).

Return to the cacodemon cage area and take the left-hand passage (southeast) this time. As you turn into this passage, you will see a blue UAC door (D). Go through this door and follow the passageways. Eventually, you will come to a dark room (E) with many square green pillars. Zig-zag your way northwest until you come to a room overlooking another nukage area.

Run straight through the nukage, heading north. Turn left and follow the passageways to the exit door (F).

Other points of interest

 * 1) At the start point, you will see a UAC door just on your right.  Behind this door is a substantial crowd of monsters guarding a chaingun (G), a berserk pack, a green armor, a radiation suit, and several large ammo pickups.
 * 2) After picking up the shotgun, if you turn left instead of right, you will enter a round room with a pentagonal nukage pool in the center.  This room contains a blue armor (H).
 * 3) At the north end of the green marble hall is a chamber (I) inhabited by a group of monsters and some barrels.  On Ultra-Violence and Nightmare!, this includes a baron of Hell, the first non-boss appearance of such.
 * 4) Past the blue door, the hallway continues around through a vine-covered area, and finally into an oblong room (J) with twelve small moving platforms.  This room contains a shell box and a medikit.

Secrets

 * 1) The central construction in the vine-covered area is actually a secret room, accessible through a door on its northwest corner, and containing a backpack (K). Note that it is not necessary to step into the slime to collect the secret. (sector 103)
 * 2) The room with the twelve moving platforms is connected to the blue armor room by a secret door. (sector 37) This door can only be opened from the north side, although it is completely unmarked on that side; it is delineated in the round room by two metal strips on the wall.
 * 3) At the south end of the green marble hall is a passageway leading to a pool of blood (L). If you drop into this pool and exit via the stairs to the north, you will find a plasma rifle (and, on UV and NM, two lost souls). (sector 65) The back end of the staircase deposits you in the blue key room.
 * 4) The blue armor room can also be exited to the east, into the vine-covered area, using a one-way door indicated by two metal strips. (sector 97) Together with secret #2 above, these two doors permit the player to pass between the start area and the shotgun/keycard area without stepping in the nukage.
 * 5)  On the platform north of the dark room with many pillars, walk east as far as possible. Step north out into the nukage and make a hairpin turn by walking around to the east. You will find a small recess south (M) containing a radiation suit.  (sector 119)
 * 6) From secret #5, go back out into the nukage and turn right. Enter the tunnel on the eastern wall, and pass into an octagonal chamber (N) containing a soul sphere. (sector 121) In the SNES version of Doom, a switch can be found here that will take the player to the episode's secret map. This was added here due to the absence of E2M5 in this version of the game.

Bugs
The backpack can sometimes be grabbed through the back wall of the secret area (sector 96).

At the north end of the oblong room, a slime trail can be seen in the form of a discoloration of the "intestinal" floor texture (see screen shot below).

The blockmap bug may be triggered by firing into the cacodemon cage at a sharp angle.

There are 3 known anomalies in this level's REJECT table.

Demo files

 * [[Media:e2m3secr.lmp|No monsters, 100% secrets walkthrough]] (file info)
 * [[Media:e2m3wik1.lmp|100% kills, items, and secrets on ITYTD]] (file info)
 * [[Media:e2m3wik2.lmp|100% kills, items, and secrets on HNTR]] (file info)
 * [[Media:e2m3wik3.lmp|100% kills, items, and secrets on HMP]] (file info)
 * [[Media:e2m3wik4.lmp|100% kills, items, and secrets on UV]] (file info)

Routes and tricks
For a straight speedrun, the shortest route seems to be:
 * go to the shotgun room via the nukage area;
 * grab the plasma gun on the way to the key, which is a slight detour, but makes up for it by punching through crowds;
 * use secret #4 as a shortcut to the blue door.

A slightly shorter route is to skip the plasma rifle altogether and run straight to the blue key; this has been used in a submission to Compet-n. This requires the rest of the map to be completed with the shotgun only, however, increasing the difficulty level.

The total time of a UV speed run hinges on how well the player can conserve cells. The current record holder proposes that, with luck, the area just beyond the blue door can be navigated with a single shotgun blast: push the rightmost lost soul out of the way, and rely on P_Random to shift the zombies toward the west wall of the passage. If nothing else, killing the final spectre with a slower weapon increases the chance of being plugged in the back. (In the NM speed style, with its doubled ammo pickups, such concerns are less apparent.)

In the dark columned room, many Compet-n entries use the strategy shown in the figure. The obstructing imp ideally should be killed with the shotgun: using only a single hitscan attack, instead of several projectiles, can make the difference between colliding or not colliding with the imp before he hits the ground.

At the start point, there is enough room to dodge the imps without first feinting to the back corner. Fire a bullet or two anyway, so that you can wallrun to the blue door without bumping into dormant troopers, and to encourage the lost souls in the dark columned room to gather in the lower corner out of your path. Similarly, some players shoot the last cacodemon to create more clearance at the opposite wall of the corridor, but it is not necessary.

Some players make a point of overshooting the plasma gun staircase in order to fake out the lost souls, although this seems ineffective with the -fast parameter. The level has been completed in both the NM speed and UV pacifist styles without the blue armor.

Modern maxkills entries begin by going straight to the green armor, emptying the chaingun into the surrounding crowd, then picking up the berserk pack and using it much more often than not (the ratio of ammo to monster health is 0.749; compare this to MAP02 of Plutonia, at 0.814). On your way from the blue key to the blue door, revisit the start area to finish off the chaingun room and to kill the caged cacodemons.

Although it is not necessary to pick up the backpack to register secret #1, take it anyway in order to kill one more cacodemon with the plasma gun. Moreover, accurate aim with the fists and plasma gun saves extra time by obviating the short detours to all three shell boxes. Some players believe that, if the chaingun must be used at all after obtaining the plasma gun, it should be confined to the corridor behind the blue door.

As a final tiny optimization, pick up the radiation suit on the way out of the chaingun room, to avoid having to wander around in search of a health pickup near the end.

In the NM100S style, the obvious detours to the secret sectors are the fastest: after taking the blue key, stay in the vine-covered area long enough to poke your head into secrets #1 and #2. With luck, nearby monsters may knock against the secret doors during infighting, causing you to spend less time passing through them.

UV -fast recordings tend to be slower than UV max recordings, because punching the baron is suddenly not a great idea. One therefore turns to the plasma gun in that room, thus increasing one's overall shotgun usage.

With respect to UV max runs, UV -respawn runs are generally optimized by neglecting the large monsters, who simply take more time to kill than humanoids and demons, and then either The first strategy seems to benefit from killing all of the imps in the dark columned room, just in case. It is also possible to save time overall by clearing the baron room twice instead of pausing near the exit, provided you can knock out the barrels from the far end of the hallway in one shot.
 * Clearing the chaingun room a second time after picking up the key; or
 * Stopping at the exit door to fire a large amount of plasma back through the window.

UV Tyson runs use the same basic plan as UV max runs, skipping the plasma gun and the second radiation suit to save time. Usually, the soul sphere is still obtained because the final cacodemon goes down much sooner at point-blank range. The fastest recordings let infighting play out in the chaingun room while the player obtains the key, and use bullets only on the caged cacodemons (clearing the entire southwestern area should build up enough stock for this). Anders Johnsen, among others, has advocated going to the key via secret #2 and returning through the slime room.

UV pacifist recordings tend to follow the UV speed route, excluding secret #3. Many players keep shooting the wall every now and then, in hopes of extracting the spectre from the last room in advance (although the doortrack may stall him on the threshold). Staying quiet in the green marble hallway seems to help you in the key room: squeeze past the first demon, absorb the initial blow, and then lunge for the key, causing him to crash into the central column and leave a clear path to the door. In the dark columned room, it may be much safer to push past the deaf lost soul, who does not necessarily assault you the moment you enter melee range, than to challenge an imp with his clawing attack. At the exit door, the small region behind each short column can make it easier to dodge everyone until the last spectre finds his way into the room. Adam Williamson has suggested that luck plays a large part in the very fastest runs, including his onetime Compet-n record wherein the sergeant fires at him and misses cleanly.

Current records
The Compet-N records for the map are:

The data was last verified in its entirety on November 11, 2012.

Map data
* The vertex count without the effect of node building is 810.

Inspiration and development
Early versions of this level appeared as E1M3 of Doom 0.3, Doom 0.4, and Doom 0.5.

Trivia

 * In the SNES version of the game, the music used in this level is "The Demons From Adrian's Pen".
 * In the Playstation/Saturn port of Doom, an arachnotron populates a room behind the cacodemon cage. As well, the player can find a BFG9000 in the small nukage pool secret room.  Neither of these are in the PC version.