Compatibility options

From ZDoom Wiki

Compatibility options are there to adjust the engine to maps that exploit bugs in older versions or in Doom(2).exe.

The following compatibility options exist. The most important ones can be set or cleared in MAPINFO as well. This allows to create special map definitions that set the needed parameters to play the map properly. If a compatibility flag is set in MAPINFO this setting will override any change through the menu or by altering the CVAR's value.

Find shortest textures like Doom

CVAR and MAPINFO name: compat_shorttex

Doom treats the first texture in the TEXTURE1 lump as no texture at all. But the function that looks for the shortest texture ignored that and checked texture 0 as well. This option re-enables this buggy behavior for old WADs that require it.

Use buggier stair building

CVAR and MAPINFO name: compat_stairs

When looking for all tagged sectors to build stairs, Doom.exe resumed the search with the last sector of the current stair, not the one following the starting sector.

Limit Pain Elementals' Lost Souls

CVAR and MAPINFO name: compat_limitpain

Doom.exe allows a maximum of 20 Lost Souls in order for a Pain Elemental to shoot more. This limit has been removed in most source ports but there are maps that require it to work properly. Doom 2's MAP09, for example, will be close to unplayable in Ultra Violence without it.

Don't let others hear your pickups

CVAR name: compat_silentpickup

Restores Doom's original behavior to play pickup sounds only for the player that is picking up an item. Obviously this option is only useful in multiplayer games.

Actors are infinitely tall

CVAR and MAPINFO name: compat_nopassover

Doom's collision code treated all actors as infinitely tall, i.e. it was impossible to jump over any solid object. Needless to say, with such a setup 3D bridges and similar effects are impossible to create. You can re-enable this effect with this option but be careful: Enabling it will seriously affect any map that expects proper z-sensitive object collision detection.

Cripple sound for silent BFG trick

CVAR name: compat_soundslots

Use this only if you can't live without the silent BFG trick! This option seriously cripples the sound system so that each actor can only play one sound at once.

Enable wall running

CVAR name: compat_wallrun

Re-enables the wallrunning bug. It is not recommended to use this option unless some map absolutely requires it. As it depends on a bug it has serious side effects on the movement code and makes any fast movement become erratic. This flag cannot be set via MAPINFO.

Spawn item drops on the floor

CVAR name: compat_notossdrops

Disables drop item tossing.

All special lines can block <use>

CVAR and MAPINFO name: compat_useblocking

Restores Doom's original behavior of any special line blocking use actions. ZDoom corrects this so that walkover actions or scrolling lines don't block uses.

Disable BOOM door light effect

CVAR and MAPINFO name: compat_nodoorlight

Disables the Boom/MBF light tag effect for doors. This is to allow maps with incorrectly tagged doors to play properly.

Raven scrollers use original speed

CVAR and MAPINFO name: compat_ravenscroll

Heretic's and Hexen's scrolling floor specials move the player much faster than the actual texture scrolling speed. Enable this option to restore this effect.

Use original sound target handling

CVAR and MAPINFO name: compat_soundtarget

ZDoom changed the sound alert handling for monsters in 2.0.90 so that the sound target is no longer preserved by a sector. While this allows more control over the actions taking place in a map it had severe side effects in many maps that spawn monsters while playing. These maps are counting on the monsters being alerted immediately and didn't bother with proper positioning because it didn't matter. This option restores the old alerting method from Doom.exe which was valid up to ZDoom 2.0.63a.

DEH health settings like Doom2.exe

CVAR and MAPINFO name: compat_dehhealth

Boom introduced a Dehacked bug which applied the max. health setting to medikits and stim packs. Originally it was only supposed to affect health bonuses. Many ZDoom maps, however, use it to limit the maximum overall health so an unconditional fix is no longer possible. Use this option to play Doom.exe compatible WADs with DEHACKED modifications that change the max. health value.

Self ref. sectors don't block shots

CVAR and MAPINFO name: compat_trace

Doom's hitscan tracing code ignores all lines with both sides in the same sector. ZDoom's does not. This option reverts to the original but less precise behavior.

Monsters get stuck over dropoffs

CVAR and MAPINFO name: compat_dropoff

This option disables the logic that allows monsters to move away from positions where they hang over a tall dropoff (e.g. the edge of a lift.) Originally a monster got stuck in such a situation. Normally there shouldn't be any need to revert to the old behavior.

Instant moving floors are not silent (development version only)

CVAR and MAPINFO name: compat_silent_instant_floor

ZDoom normally disables the stop sound for floors that move instantly from one height to another. Enable this setting to make the stop sound be played in these special cases.

Interpolate monster movement

CVAR name: nomonsterinterpolation

Disables movement interpolation for any movement by the monster AI code. Depending on your preferences interpolating this might look odd.