Difference between revisions of "Engine bug"
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** Most bugs are due to ''algorithms'' which fail to account for all possible inputs, apply conditional statements in an illogical sequence, or have unforeseen consequences in particular game situations. | ** Most bugs are due to ''algorithms'' which fail to account for all possible inputs, apply conditional statements in an illogical sequence, or have unforeseen consequences in particular game situations. | ||
*** A few of these arise from simple ''typos'' in the source code. | *** A few of these arise from simple ''typos'' in the source code. | ||
− | ** Improperly constructed ''[[linedef]]s'' | + | ** Improperly constructed ''[[linedef]]s'' (with orphaned [[tag]]s or incorrectly placed [[texture]]s) or ''[[sector]]s'', can also induce various strange behaviors. |
** The Doom engine includes few safeguards against [[Wikipedia:Arithmetic overflow|''overflow'' conditions]]. | ** The Doom engine includes few safeguards against [[Wikipedia:Arithmetic overflow|''overflow'' conditions]]. | ||
** Line-of-sight calculations, [[Doom rendering engine|rendering]] algorithms, and the [[Doom rendering engine#Node building|BSP tree]] are also susceptible to [[Wikipedia:Floating point#Accuracy problems|''roundoff'' errors]]. | ** Line-of-sight calculations, [[Doom rendering engine|rendering]] algorithms, and the [[Doom rendering engine#Node building|BSP tree]] are also susceptible to [[Wikipedia:Floating point#Accuracy problems|''roundoff'' errors]]. | ||
− | ** The engine imposes a number of ''static limits'' on [[Thing]] placement and map construction, which sometimes fix one problem by creating another. | + | ** The engine imposes a number of ''[[static limits]]'' on [[Thing]] placement and map construction, which sometimes fix one problem by creating another. |
* '''Fatal''' bugs are those where the engine crashes (often with the [[Venetian blind crash|Venetian blind]] effect) or else exits the game in a controlled fashion, usually with an [[error message]]. '''Y*''' means that termination is possible, but not inevitable. '''N*''' means that the program keeps running, but that rendering or character behavior may be sufficiently compromised that meaningful gameplay becomes impossible. | * '''Fatal''' bugs are those where the engine crashes (often with the [[Venetian blind crash|Venetian blind]] effect) or else exits the game in a controlled fashion, usually with an [[error message]]. '''Y*''' means that termination is possible, but not inevitable. '''N*''' means that the program keeps running, but that rendering or character behavior may be sufficiently compromised that meaningful gameplay becomes impossible. | ||
Line 25: | Line 25: | ||
* A bug is a '''loophole''' if it can be abused to the player's advantage (especially during [[speedrun]]s or [[deathmatch]]es). | * A bug is a '''loophole''' if it can be abused to the player's advantage (especially during [[speedrun]]s or [[deathmatch]]es). | ||
− | {| {{ | + | {| {{prettySortable}} |
!Phenomenon | !Phenomenon | ||
!Canonicity | !Canonicity | ||
Line 41: | Line 41: | ||
! N | ! N | ||
! Y | ! Y | ||
+ | |- | ||
+ | | [[1% damage bug]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Absurd texture name in error message]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! Y* | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
|- | |- | ||
| [[AASTINKY|AASTINKY and AASHITTY]] | | [[AASTINKY|AASTINKY and AASHITTY]] | ||
Line 54: | Line 70: | ||
| Overflow | | Overflow | ||
! N* | ! N* | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Anomalous angry face behavior]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Arch-Vile fire spawned at the wrong location]] | ||
+ | | Undisputed | ||
+ | | Typo | ||
+ | ! N | ||
! N | ! N | ||
! N | ! N | ||
Line 64: | Line 96: | ||
! Y | ! Y | ||
! S | ! S | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Baron attacks a monster behind him]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
! N | ! N | ||
|- | |- | ||
Line 89: | Line 129: | ||
! N | ! N | ||
! Y | ! Y | ||
+ | |- | ||
+ | | [[Blockmap overflow]] | ||
+ | | Undisputed | ||
+ | | Overflow | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
|- | |- | ||
| [[Broadcast packet meltdown]] | | [[Broadcast packet meltdown]] | ||
Line 109: | Line 157: | ||
| Undisputed | | Undisputed | ||
| Algorithm | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Colormap blink ignores concurrent powerup]] [http://www.doomworld.com/vb/showthread.php?s=&postid=1019768#post1019768] | ||
+ | | | ||
+ | | | ||
! N | ! N | ||
! N | ! N | ||
Line 145: | Line 201: | ||
! N | ! N | ||
! N | ! N | ||
+ | |- | ||
+ | | [[Demon speed bug]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! Y* | ||
+ | ! N | ||
+ | ! | ||
+ | ! Y | ||
|- | |- | ||
| [[Seg#Drawsegs overflow|Drawsegs overflow]] | | [[Seg#Drawsegs overflow|Drawsegs overflow]] | ||
Line 155: | Line 219: | ||
|- | |- | ||
| [[Elastic collisions with walls]] | | [[Elastic collisions with walls]] | ||
− | | | + | | Undisputed |
− | | | + | | Roundoff |
! N | ! N | ||
! N | ! N | ||
Line 180: | Line 244: | ||
| [[Final Doom teleporters do not set Z coordinate]] | | [[Final Doom teleporters do not set Z coordinate]] | ||
| Undisputed | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Firing frame position not updated when the player dies]] | ||
+ | | | ||
| Algorithm | | Algorithm | ||
! N | ! N | ||
Line 226: | Line 298: | ||
! N | ! N | ||
|- | |- | ||
− | | Hall of Mirrors effect (limit) | + | | [[Static_limits#Drawsegs|Hall of Mirrors effect (limit)]] |
| Undisputed | | Undisputed | ||
| Algorithm | | Algorithm | ||
Line 234: | Line 306: | ||
! N | ! N | ||
|- | |- | ||
− | | [[Hall of Mirrors effect | + | | [[Hall of Mirrors effect|Hall of Mirrors effect (missing texture)]] |
| Undisputed | | Undisputed | ||
| Linedef | | Linedef | ||
Line 264: | Line 336: | ||
! | ! | ||
! | ! | ||
+ | ! | ||
+ | |- | ||
+ | | [[Chainsaw#Notes|IDCHOPPERS cheat confers 1 tic of invulnerability]] | ||
+ | | | ||
+ | | Typo | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
! | ! | ||
|- | |- | ||
Line 278: | Line 358: | ||
| Algorithm | | Algorithm | ||
! Y | ! Y | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Inaccurate trigonometry table]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N | ||
! N | ! N | ||
! N | ! N | ||
Line 321: | Line 409: | ||
! N | ! N | ||
! Y | ! Y | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
|- | |- | ||
| [[Linedef type 37]] | | [[Linedef type 37]] | ||
Line 352: | Line 432: | ||
! N | ! N | ||
! S | ! S | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Lopsided final boss explosions]] | ||
+ | | Undisputed | ||
+ | | Typo | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
! N | ! N | ||
|- | |- | ||
Line 408: | Line 496: | ||
! N | ! N | ||
! N | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Manual doors on 1S lines cause an illegal operation]] | ||
+ | | Undisputed | ||
+ | | Linedef | ||
+ | ! Y* | ||
+ | ! N | ||
+ | ! Y | ||
! N | ! N | ||
|- | |- | ||
Line 488: | Line 584: | ||
! N | ! N | ||
! S | ! S | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Moving platform heights not preserved in saved games]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Negative vertical offsets are ignored in texture patches]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
! N | ! N | ||
|- | |- | ||
Line 541: | Line 653: | ||
| | | | ||
| | | | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Pause bug in menus with scroll bars]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
! N | ! N | ||
! N | ! N | ||
Line 617: | Line 737: | ||
! | ! | ||
! | ! | ||
+ | |- | ||
+ | | [[PWAD size limit]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | !Y | ||
+ | !N | ||
+ | !Y | ||
+ | !N | ||
|- | |- | ||
| [[Quantum lost soul]] | | [[Quantum lost soul]] | ||
Line 628: | Line 756: | ||
| [[Raising sectors change to orphaned sector type]] | | [[Raising sectors change to orphaned sector type]] | ||
| Disputed | | Disputed | ||
− | | | + | | Sector |
+ | !N | ||
+ | !N | ||
+ | !Y | ||
+ | !N | ||
+ | |- | ||
+ | | [[Random sound pitch removed]] | ||
+ | | | ||
+ | | | ||
!N | !N | ||
!N | !N | ||
Line 640: | Line 776: | ||
! N | ! N | ||
! N | ! N | ||
+ | ! Y | ||
+ | |- | ||
+ | | [[Blast damage#Non-reentrancy|Recurrent blast damage]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! S | ||
! Y | ! Y | ||
|- | |- | ||
Line 647: | Line 791: | ||
! Y | ! Y | ||
! Y | ! Y | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Revenant tracers desync internal demos]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N* | ||
+ | ! N | ||
! N | ! N | ||
! N | ! N | ||
Line 676: | Line 828: | ||
| [[Screen melt effect during Doom II cast sequence]] | | [[Screen melt effect during Doom II cast sequence]] | ||
| | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Secret level|Secret exit idiosyncrasies]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! Y | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Secret#Bugs|Secret sectors appear or disappear]] | ||
+ | | | ||
+ | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! S | ||
+ | ! N | ||
+ | |- | ||
+ | |[[Sector type 17 is disabled after loading a saved game]] | ||
+ | | Undisputed | ||
| Algorithm | | Algorithm | ||
! N | ! N | ||
Line 686: | Line 862: | ||
| Static limit | | Static limit | ||
! N | ! N | ||
+ | ! N | ||
+ | ! N | ||
+ | ! Y | ||
+ | |- | ||
+ | | [[Single-use line actions can fail]] | ||
+ | | Undisputed | ||
+ | | Algorithm | ||
+ | ! N* | ||
! N | ! N | ||
! N | ! N | ||
Line 698: | Line 882: | ||
! | ! | ||
|- | |- | ||
− | | [[Sky hack]] | + | | [[Sky hack absorbs attacks regardless of height]] |
| Undisputed | | Undisputed | ||
| Algorithm | | Algorithm | ||
Line 821: | Line 1,005: | ||
| Disputed | | Disputed | ||
| Algorithm | | Algorithm | ||
+ | ! N | ||
+ | ! N | ||
+ | ! Y | ||
+ | ! N | ||
+ | |- | ||
+ | | [[Starting on a vertex between visplanes causes illegal memory access]] | ||
+ | | Undisputed | ||
+ | | | ||
! N | ! N | ||
! N | ! N |
Revision as of 16:04, 30 November 2014
A Doom engine bug is a limitation or an oddity present in the Doom engine. For errors in map design, even those related to a specific item below, see the article about that map.
Note that playing with a source port may, while removing some or even the majority of the bugs listed below, introduce other bugs which are not listed here (although details may be present in the article about the source port in question).
Key
This table classifies anomalies in a very broad way; see the individual articles for details.
- Canonicity — A bug is verified only when a current or former id Software programmer has called it a bug in a public medium. An unverified bug may still be undisputed if it is generally accepted as an error or issue by the fan community under a consensus involving thorough playtesting and research on the corresponding phenomenon and any associated binaries or source code. A bug is disputed if it can be argued to be a harmless and possibly intentional feature.
- Cause — The general category of underlying problem:
- Most bugs are due to algorithms which fail to account for all possible inputs, apply conditional statements in an illogical sequence, or have unforeseen consequences in particular game situations.
- A few of these arise from simple typos in the source code.
- Improperly constructed linedefs (with orphaned tags or incorrectly placed textures) or sectors, can also induce various strange behaviors.
- The Doom engine includes few safeguards against overflow conditions.
- Line-of-sight calculations, rendering algorithms, and the BSP tree are also susceptible to roundoff errors.
- The engine imposes a number of static limits on Thing placement and map construction, which sometimes fix one problem by creating another.
- Most bugs are due to algorithms which fail to account for all possible inputs, apply conditional statements in an illogical sequence, or have unforeseen consequences in particular game situations.
- Fatal bugs are those where the engine crashes (often with the Venetian blind effect) or else exits the game in a controlled fashion, usually with an error message. Y* means that termination is possible, but not inevitable. N* means that the program keeps running, but that rendering or character behavior may be sufficiently compromised that meaningful gameplay becomes impossible.
- A bug has a workaround if it can be avoided by reasonable compromises in map design, such as when matching every linedef tag to at least one sector, but not when removing invulnerabilities from every level containing a sky texture, or also by convenient precautions and other measures taken by the program user, such as when increasing the mouse sensitivity through the configuration file directly, instead of using the menu. S means that the bug can be avoided only by making one's map smaller or less complex.
- A bug is a loophole if it can be abused to the player's advantage (especially during speedruns or deathmatches).