Difference between revisions of "Engine bug"
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A [[Doom]] '''engine bug''' is a limitation or an oddity present in the [[Doom engine]]. For errors in [[Levels|map]] design, even those related to a specific item below, see the article about that map. | A [[Doom]] '''engine bug''' is a limitation or an oddity present in the [[Doom engine]]. For errors in [[Levels|map]] design, even those related to a specific item below, see the article about that map. | ||
− | This article uses the 1.9 | + | This article uses the version 1.9 [[DOOM2.EXE]] DOS version as the base version. Older versions, the source release, Final Doom and The Ultimate Doom have some minor changes, tweaks and different bugs. |
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). | 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). | ||
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This table classifies anomalies in a very broad way; see the individual articles for details. | This table classifies anomalies in a very broad way; see the individual articles for details. | ||
− | * ''' | + | * '''{{wp|Canon (fiction)|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 {{wp|Executable|binaries}} or [[Doom source code|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: | * '''Cause''' — The general category of underlying problem: | ||
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*** 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'' (with orphaned [[tag]]s or incorrectly placed [[texture]]s) or ''[[sector]]s'', can also induce various strange behaviors. | ** 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 | + | ** The Doom engine includes few safeguards against {{wp|Integer 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 | + | ** Line-of-sight calculations, [[Doom rendering engine|rendering]] algorithms, and the [[Doom rendering engine#Node building|BSP tree]] are also susceptible to {{wp|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. | ||
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* 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). | ||
− | === Bugs present in Doom | + | === Bugs present in Doom II version 1.9 for DOS === |
{| {{prettySortable}} | {| {{prettySortable}} | ||
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|} | |} | ||
− | === Bugs present in versions prior to Doom | + | === Bugs present in versions prior to Doom II version 1.9 for DOS === |
{| {{prettySortable}} | {| {{prettySortable}} | ||
!Phenomenon | !Phenomenon |
Revision as of 04:07, 17 March 2018
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.
This article uses the version 1.9 DOOM2.EXE DOS version as the base version. Older versions, the source release, Final Doom and The Ultimate Doom have some minor changes, tweaks and different bugs.
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).
Contents
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).