Update

doom.md

@@ -1,6 +1,6 @@
 # Doom
 
-Doom is a legendary video [game](game.md) released in December [1993](1990s.md), perhaps the most famous video game of all time, the game that popularized the [first man shooter](first_person_shooter.md) genre and shocked by its at the time extremely advanced [3D](pseudo_3D.md) graphics (yes, **Doom is 3D**) and caused one of the biggest revolutions in video game history. It was made by [Id Software](id_software.md), most notably by [John Carmack](john_carmack.md) (graphics + engine programmer) and [John Romero](john_romero.md) (tool programmer + level designer) -- all in all the game was developed by about 5 to 6 men in about a year. Doom is sadly [proprietary](proprietary.md), it was originally distributed as [shareware](shareware.md) (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 [free (as in freedom) software](free_software.md) under [GPL](gpl.md) which gave rise to many source [ports](port.md) and "improved" "[modern](modern.md)" 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 [Freedoom](freedoom.md) project that has created [free as in freedom](free_culture.md) asset replacements for the game. [Anarch](anarch.md) is an official [LRS](lrs.md) game inspired by Doom, completely in the [public domain](public_domain.md).
+Doom is a legendary video [game](game.md) released in December [1993](1990s.md), perhaps the most famous video game of all time, the game that popularized the [first man shooter](first_person_shooter.md) genre and shocked by its at the time extremely advanced 3D graphics (yes, **Doom is 3D**) and caused one of the biggest revolutions in video game history. It was made by [Id Software](id_software.md), most notably by [John Carmack](john_carmack.md) (graphics + engine programmer) and [John Romero](john_romero.md) (tool programmer + level designer) -- all in all the game was developed by about 5 to 6 men in about a year. Doom is sadly [proprietary](proprietary.md), it was originally distributed as [shareware](shareware.md) (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 [free (as in freedom) software](free_software.md) under [GPL](gpl.md) which gave rise to many source [ports](port.md) and "improved" "[modern](modern.md)" 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 [Freedoom](freedoom.md) project that has created [free as in freedom](free_culture.md) asset replacements for the game. [Anarch](anarch.md) is an official [LRS](lrs.md) game inspired by Doom, completely in the [public domain](public_domain.md).
 
 Doom has a cool wiki at https://doomwiki.org.
 
@@ -39,7 +39,7 @@ The code itself looks alright, files are nicely organized into groups by their p
 
 The game only used [fixed point](fixed_point.md), no [float](float.md)!
 
-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 [Wolf3D](wolf3D.md) 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 [GPUs](gpu.md) in a race for more and more impressive visuals). Doom used a technique called **[BSP rendering](bsp.md)** (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 [realtime](realtime.md) 3D views of textured (all walls, floors and ceilings) environments with primitive lighting (per-sector plus diminishing lighting), enemies and items represented by 2D [billboards](billboard.md) ("[sprites](sprite.md)"). No [GPU](gpu.md) acceleration was used, graphics was rendered purely with [CPU](cpu.md) (so called [software rendering](sw_rendering.md), GPU rendering would come with Doom's successor [Quake](quake.md), 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 "[pseudo 3D](pseudo3d.md)" 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 [Build](build_engine.md) engine that ran games like [Duke Nukem 3D](duke_3d.md), Blood and Shadow Warrior. All of these 90s shooters were amazing in their visuals and looked far better than any [modern](modern.md) 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).
+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 [Wolf3D](wolf3D.md) 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 [GPUs](gpu.md) in a race for more and more impressive visuals). Doom used a technique called **[BSP rendering](bsp.md)** (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 [realtime](realtime.md) 3D views of textured (all walls, floors and ceilings) environments with primitive lighting (per-sector plus diminishing lighting), enemies and items represented by 2D [billboards](billboard.md) ("[sprites](sprite.md)"). No [GPU](gpu.md) acceleration was used, graphics was rendered purely with [CPU](cpu.md) (so called [software rendering](sw_rendering.md), GPU rendering would come with Doom's successor [Quake](quake.md), 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 "[pseudo 3D](pseudo3d.md)" 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 [Build](build_engine.md) engine that ran games like [Duke Nukem 3D](duke3d.md), Blood and Shadow Warrior. All of these 90s shooters were amazing in their visuals and looked far better than any [modern](modern.md) 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).
 
 The game data is stored in so called **WAD files** (short for *where's all the data*). While many things are hardcoded in the engine, such as the total number of levels or types of weapons, most other things such as textures, levels, color palettes, weapons and enemy sprites are in the WAD files and so can be replaced without having to mess with the engine itself. There are two types of WAD files (both however still come with the same .wad extension, they are distinguished only by the file magic number): IWAD (internal WAD) and PWAD ([patch](patch.md) WAD). IWAD is the most important one, representing the base game, so for example Doom, Hexen and Freedoom will all have their own specific IWAD. Only one IWAD is loaded at any time. PWAD allows to add or modify things in the IWAD which makes it possible to easily correct bugs in the game data and make mods. Unlike with IWADs, multiple PWADs can be loaded at any time -- when loaded, a resource that's present in the PWAD will override the same resource in the base IWAD. All resources in the WAD files are stored as so called *lumps* which we may simply see as "blobs of data" or "files". A nice [CLI](cli.md) tool for working with WADs is e.g. [deutex](deutex.md).