Doom
Doom is a legendary video [1]game released in December [2]1993, perhaps
the most famous video game of all time, the game that popularized the
[3]first man shooter genre and shocked by its at the time extremely
advanced [4]3D graphics (yes, Doom is 3D) and caused one of the biggest
revolutions in video game history. It was made by [5]Id Software, most
notably by [6]John Carmack (graphics + engine programmer) and [7]John
Romero (tool programmer + level designer) -- all in all the game was
developed by about 5 to 6 men in about a year. Doom is sadly
[8]proprietary, it was originally distributed as [9]shareware (a gratis
"demo" was available for playing and sharing with the option to buy a full
version). However the game engine was later (1999) released as [10]free
(as in freedom) software under [11]GPL which gave rise to many source
[12]ports and "improved" "[13]modern" engines (which however look like
shit, the original looks by far the best, if you want to play Doom use
Chocolate Doom or Crispy Doom, avoid anything with GPU rendering). The
assets remain non-free but a completely free alternative is offered by the
[14]Freedoom project that has created [15]free as in freedom asset
replacements for the game. [16]Anarch is an official [17]LRS game inspired
by Doom, completely in the [18]public domain. Doom named a whole
generation of so called [19]doomers.
Doom has a cool wiki at https://doomwiki.org.
{ Great books about Doom I can recommend: Masters of Doom (about the
development) and Game Engine Black Book: Doom (details about the engine
internals). ~drummyfish }
Partially thanks to the release of the engine under a [20]FOSS license and
its relatively [21]suckless design ([22]C language, [23]software
rendering, ...), Doom has been [24]ported, both officially and
unofficially, to a great number of platforms (e.g. [25]Gameboy Advance,
[26]PS1, even [27]SNES) and has become a kind of de facto standard
[28]benchmark for computer platforms -- you will often hear the phrase:
"but does it run Doom?" Porting a Doom to any platform has become kind of
a [29]meme, someone allegedly even ported it to a pregnancy test (though
it didn't actually run on the test, it was really just a display). { Still
[30]Anarch may be even more portable than Doom :) ~drummyfish }
The major leap that Doom engine's graphics brought was unprecedented,
however Doom was not just a game with good graphics, it had extremely good
gameplay, legendary [31]music and art style and introduced the
revolutionary [32]deathmatch multiplayer (the name deathmatch itself was
coined by Romero during Doom multiplayer sessions), as well as a HUGE
modding and mapping community. It was a success in every way -- arguably
no other game has since achieved a greater revolution than Doom (no, not
even [33]Minecraft, [34]World of Warcraft etc.). Many reviews of it just
went along the lines: "OK, Doom is the best game ever made, now let's just
take a look at the details...". The game's style was also extremely cool,
as were the developers themselves, Doom was very appealing by its sincere
style of simply being a pure metal/bloody/gory/demon slaying shooter
without any corporate garbage stuffed in for more popularity that you'd
see today. It was simply a game made by a few guys who did it the way they
liked it without giving shit about anything, you won't see that anymore,
Doom simply didn't pretend to be some kind of pompous, glorious work and
so for example didn't give much shit about the backstory, everyone knew
the game was about shooting and so they just made it a bloody shooter.
John Carmack famously stated that story in a video game is like story in a
porn movie -- it's expected to be there but not very important. Nowadays
you may see developers try to imitate this attitude but it's always
laughable, it will only ever be a pretense because the times when you
could simply make a game with artistic freedom, without having to bow to
managers, gender departments, publishers and other overlords are simply
long gone.
Doom wasn't the first 3D game, nor was it the first FPS, there were games
before that were "more 3D" in a sense -- for example flight simulators --
what was special about Doom was how it used all the graphic tricks and
combined them with excellent gameplay to achieve unprecedented
"immersion", such that many weren't ready for. For example Doom had fully
textured environments, including floors and ceilings, which along with the
fog and lighting made the player really feel present in the game despite
not being able to e.g. look up and down.
As stated, the game's backstory was simple and didn't stand in the way of
gameplay, it's basically about a tough marine (so called Doomguy) on a
Mars military base slaying hordes of demons from hell, all in a rock/metal
style with a lot of gore and over-the-top violence (chain saws n stuff).
Doom was followed by Doom II in 1995, which "content-wise" was basically
just a data disc, the same game with new levels and some minor additions.
Later there were some other releases and rereleases, notable is Doom III
from 2004, Doom 2016 ("reboot") and Doom: Eternal (2020).
Some [35]interesting things about Doom:
* Someone created a Doom system monitor for [36]Unix systems called
[37]psDooM where the monsters in game are the operating system
[38]processes and killing the monsters kills the processes.
* Someone (kgsws) has been [39]hacking the ORIGINAL Doom engine in an
impressive way WITHOUT modifying the source code or the binary, rather
using [40]arbitrary code execution bug; he added very advanced
features known from newer source ports, for example an improved 3D
rendering algorithms allowing geometry above geometry etc. (see e.g.
https://yt.artemislena.eu/watch?v=RdbRPNPUWlU). It's called the Ace
engine.
* Doom sprites were made from photos of physical things: weapons are
modified photos of toys, enemies were made from clay and then
photographed from multiple angles (actually a great alternative to
[41]3D modeling that's less dependent on computers and produces more
realistic results).
* The strongest weapon in the game is name BFG9000, which stands for
"big fucking gun".
* There is some kind of "controversial" Doom mod called Moon Man where
you shoot feminists, jews, niggas and such, apparently it triggers
[42]SJWs or something.
* TODO
Doom Engine/Code
See also [43]game engine for the list of different Doom engines.
Doom source code is written in [44]C89 and is about 36000 [45]lines of
code long. The original system requirements stated roughly a 30 MHz
[46]CPU and 4 MB [47]RAM as a minimum. It had 27 levels (9 of which were
shareware), 8 weapons and 10 enemy types. The engine wasn't really as
flexible in a way "[48]modern" programmers expect, many things were hard
coded, there was no [49]scripting or whatever (see? you don't fucking need
it), new games using the engine had to usually modify the engine
internals.
The code itself looks alright, files are nicely organized into groups by
their prefix (g_: game, r_: rendering, s: sound etc.). The same goes for
the function names. There seems to be tabs mixed with spaces though,
sometimes a bit shitty formatting, but overall MUCH better than [50]duke
3D's code (well, that doesn't say much though). [51]Comments are
plentiful.
The game only used [52]fixed point, no [53]float!
The Doom engine (also called id Tech 1) was revolutionary and advanced
(not only but especially) video game graphics by a great leap, considering
its predecessor [54]Wolf3D was really primitive in comparison (Doom
basically set the direction for future trends in games such as driving the
development of more and more powerful [55]GPUs in a race for more and more
impressive visuals). Doom used a technique called [56]BSP rendering
(levels were made of convex 2D sectors that were then placed in a BSP tree
which helped quickly sort the walls for rendering front-to-back) that was
able to render [57]realtime 3D views of textured (all walls, floors and
ceilings) environments with primitive lighting (per-sector plus
diminishing lighting), enemies and items represented by 2D [58]billboards
("[59]sprites"). No [60]GPU acceleration was used, graphics was rendered
purely with [61]CPU (so called [62]software rendering, GPU rendering would
come with Doom's successor [63]Quake, and would also later be brought to
Doom by newer community made engines, though the original always looks the
best). This had its limitations, for example the camera could not look up
and down, there could be no tilted walls and the levels could not have
rooms above other rooms. The geometry of levels was only static, i.e. it
could not change during play (only height of walls could), because
rendering was dependent on precomputed BSP trees (which is what made it so
fast). For these reasons some call Doom "[64]pseudo 3D" or 2.5D rather
than "true 3D", some retards took this even as far as calling Doom 2D with
its graphics being just an "illusion", as if literally every 3D graphics
ever wasn't a mere illusion. Nevertheless, though with limitations, Doom
did present 3D views and internally it did work with 3D coordinates (for
example the player or projectiles have 2D position plus height
coordinate), despite some dumb YouTube videos saying otherwise. For this
reason we prefer to call Doom a primitive 3D engine, but 3D nonetheless.
Other games later used the Doom engine, such as Heretic, Hexen and Strife.
The Doom engine was similar to and competing with [65]Build engine that
ran games like [66]Duke Nukem 3D, Blood and Shadow Warrior. All of these
90s shooters were amazing in their visuals and looked far better than any
[67]modern shit. Build engine games had similar limitations to those of
the Doom engine but would improve on them (e.g. faking looking up and down
by camera tilting, which could in theory be done in Doom too, or allowing
sloped floor and dynamic level geometry).
Indexed ([68]palette) mode with "only" 256 colors was used for rendering.
Precomputed color tables were used to make dimming of colors faster.
Similarly a [69]look up table was used for [70]random number generation --
two independent [71]pseudorandom generators are present, one is used for
things such as visual effects while the other one is utilized purely for
the game simulation so that it stays deterministic independently on
graphics etc.
Doom also has a [72]deterministic [73]FPS-independent physics which allows
for efficient recording of [74]demos of its gameplay and creating [75]tool
assisted speedruns, i.e. the time step of game simulation is fixed (35
tics per second). Such demos can be played back in high quality while
being minuscule in size and help us in many other ways, for example for
verifying validity of [76]speedruns. This is very nice and serves as an
example of a well written engine (unlike later engines from the same
creators, e.g. those of [77]Quake games which lacked this feature -- here
we can see how things get progressively shittier in computer technology as
we go forward in time).
There is no [78]antialiasing in the engine, i.e. aliasing can be noticed
on far-away textures, but it is suppressed by the use of low-res textures
and dimming far-away areas. There is also no edge smoothing (kind of
misleadingly known as "antialiasing") in the geometry rendering, the
engine is [79]subpixel accurate in rendering of the top and bottoms of the
walls, i.e. the line these boundaries form may result in rasterizing
slightly different pixels even if the start and end pixel is the same,
depending on the subpixel position of the start and endpoint -- this
feature doesn't much help in static screenshots but makes animation nicer.
See Also
* [80]Anarch
* [81]Duke 3D
* [82]Gloom (fun [83]Amiga Doom clone)
* [84]Quake
* [85]Postal
* [86]Jedi engine
* [87]Build engine
* [88]Chasm: The Rift
* [89]raycasting
Links:
1. game.md
2. 1990s.md
3. first_person_shooter.md
4. pseudo_3D.md
5. id_software.md
6. john_carmack.md
7. john_romero.md
8. proprietary.md
9. shareware.md
10. free_software.md
11. gpl.md
12. port.md
13. modern.md
14. freedoom.md
15. free_culture.md
16. anarch.md
17. lrs.md
18. public_domain.md
19. doomer.md
20. foss.md
21. suckless.md
22. c.md
23. sw_rendering.md
24. port.md
25. gba.md
26. playstation.md
27. snes.md
28. benchmark.md
29. meme.md
30. anarch.md
31. music.md
32. deathmatch.md
33. minecraft.md
34. wow.md
35. interesting.md
36. unix.md
37. psdoom.md
38. process.md
39. hacking.md
40. arbitrary_code_execution.md
41. 3d_model.md
42. sjw.md
43. game_engine.md
44. c.md
45. loc.md
46. cpu.md
47. ram.md
48. modern.md
49. script.md
50. duke3D
51. comment.md
52. fixed_point.md
53. float.md
54. wolf3D.md
55. gpu.md
56. bsp.md
57. realtime.md
58. billboard.md
59. sprite.md
60. gpu.md
61. cpu.md
62. sw_rendering.md
63. quake.md
64. pseudo3d.md
65. build_engine.md
66. duke_3d.md
67. modern.md
68. palette.md
69. lut.md
70. rng.md
71. pseudorandomness.md
72. determinism.md
73. fps.md
74. demo.md
75. tas.md
76. speedrun.md
77. quake.md
78. antialiasing.md
79. subpixel.md
80. anarch.md
81. duke3d.md
82. gloom.md
83. amiga.md
84. quake.md
85. postal.md
86. jedi_engine.md
87. build_engine.md
88. chasm_the_rift.md
89. raycasting.md