Using IWADS as PWADS

Using IWADs as PWADs is a niche technique that can be useful in certain cases. For example, it can be used to play a game with resources of a different one, such as playing Chex Quest with graphics and sounds from Doom. Below are listed all the possible use cases of this technique.

This article only relates to the original DOS executable, behavior in source ports may vary.

Doom and Doom II

Playing Doom while using DOOM2.WAD as a PWAD or vice versa changes very little, with most of the content being taken from the IWAD game. The changes include:

• Using the title screen and the menu graphic of the PWAD game.
• Using the demos of the PWAD game.
• Changing or breaking certain textures.
• Using the skies of the PWAD game.

Attempting to play Doom while using any of the alpha or beta IWADs as PWADs will crash the game.

Final Doom

Playing Doom II while using either of the Final Doom IWADs as PWADs will cause the end result to be nearly indistinguishable from simply playing these IWADs in the intended way, with the only visible difference being the level names on the automap being those from Doom II, rather than the IWADs. This effect is pointless in modern source ports, however, it could be useful in the original DOS executable to play both Final Doom and Doom II from the same executable, rather than having to switch them, since it cannot select IWADs, but rather is hardcoded to use DOOM2.WAD.

Playing Doom while using either of the Final Doom IWADs as PWADs will cause the same changes as playing while using DOOM2.WAD as a PWAD.

Heretic and Hexen

Playing Doom or Doom II while using HERETIC.WAD or HEXEN.WAD as a PWAD will simply not run, and get stuck on the initialization screen; this is due to an incompatibility of the engines, with both adding features the vanilla Doom doesn't support.

Playing Hexen using DOOM.WAD, DOOM2.WAD or HERETIC.WAD as a PWAD results in an "R_TextureNumForName: %s not found" error message.

Playing Heretic using DOOM.WAD, DOOM2.WAD or HEXEN.WAD as a PWAD results in the game freezing while initializing for DOOM.WAD and HEXEN.WAD or generates several "R_GenerateLookup: column without a patch" errors for DOOM2.WAD.

Strife

Attempting to run Doom or Doom II while using STRIFE1.WAD as a PWAD will crash the game due to it attempting to allocate 4294966172 bytes in memory. This is due to the format of the TEXTURE1 and TEXTURE2 lumps differing from that used by vanilla Doom, causing an invalid size to be calculated.

Attempting to run Strife while using DOOM.WAD or DOOM2.WAD as a PWAD will crash the game due to missing textures.

Doom 64

Attempting to play any game while using DOOM64.WAD as a PWAD will crash the game after attempting to play any level due to the fact that all the graphics are stored inside PNGs, which none of the vanilla executables support.

Playing Doom 64 while using the IWAD of any game as a PWAD will cause no changes.

Chex Quest

Playing Doom while using CHEX.WAD as a PWAD or vice versa will inherit the strings and the enemy behavior of the base game, but will take everything else from the PWAD game.

Playing Heretic while using CHEX.WAD or CHEX2.WAD will freeze during initalization, with Hexen giving "R_TextureNumForName: SKYWALL not found" error messages.

Playing Chex Quest while using DOOM2.WAD as a PWAD will cause all the assets to be changed to the ones from Doom. While there are a few broken textures, it generally works very well, and is perhaps the most well-known use of this trick. Playing Doom II while using CHEX.WAD as a PWAD will cause all the game's assets to be changed to the ones from Chex Quest, except with a much higher amount of broken textures. Additionally, all the enemies and weapons introduced in Doom II will maintain their sprites, causing them to clash with the cartoon style of everything else.

Running a game with its own files

Occasionally, running a game with its own files as a PWAD is beneficial. This exclusively has an effect in the case of playing later re-releases with the original files, such as playing Doom Classic with the v1.9 IWAD loaded as a PWAD in order to restore original assets. Normally, this isn't very useful, since it is trivial to replace an IWAD with another one. The one place this might be useful is in the Android version of the Doom Classic Unity port, where the IWADs are inaccessible without root access. Meanwhile PWADs can easily be loaded by adding them to Android/data/com.bethsoft.doom/files/WADs for Doom and Android/data/com.bethsoft.doom2/files/WADs for Doom II, then played with by selecting them in-game. This can be used to restore the red crosses on medikits, the swastikas on the textures in the secret levels of Doom II, the Nine Inch Nails logo in E4M1, and other things that were changed between the versions.

Screenshots

Vanilla

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  Playing Doom while using DOOM2.WAD as a PWAD results in a lot of broken textures.

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  The most well-known use case for this trick, running DOOM2.WAD as a PWAD in Chex Quest causes all assets to be replaced with those from Doom.

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  The pain elemental stands out as the sole realistic graphic in the entire scene, caused by running Doom II with CHEX.WAD as a PWAD.

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  Running DOOM2.WAD as a PWAD in the Android version of Doom II to restore the red crosses on medikits and the swastikas on the walls.

Non-vanilla

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  Playing Doom while using HERETIC.WAD as a PWAD results in the HUD being discolored.

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  Playing Doom II while using HERETIC.WAD as a PWAD results in all textures and the palette being broken.

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  You'll be facing tough resistance from the very beginning if you choose to play Heretic with DOOM.WAD as a PWAD.

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  The spiderdemon in level 2 of Hexen, placed there by running HEXEN.WAD as a PWAD in Doom II.