Using ZIPs as WAD replacement

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For more information on this article, visit the PK3 page on the Doom Wiki.
PK3 redirects here. The PK3 file format is the same as the ZIP file format, and is treated exactly the same by ZDoom.

ZDoom allows using several compressed archive formats instead of the traditional WADs. Most notably:

MiniWikipediaLogoIcon.pngZIP
A .zip file used as the container for a ZDoom mod is usually given either the .pk3 extension (originally used by Quake 3,) .pkz (for ZDoom,) .pke (for Eternity Engine) or .ipk3 (for full-game ZIPs) instead of .zip. While there is no technical difference, this helps avoid potential confusion from users thinking the mod should be extracted from it, and also prevents Windows from presenting it as a directory. ZDoom supports several ZIP archiving methods: stored (no compression), shrunk, imploded, MiniWikipediaLogoIcon.pngdeflated (the most commonly used), MiniWikipediaLogoIcon.pngbzip2 and MiniWikipediaLogoIcon.pngLZMA algorithms. Note that many ZIP utilities only partially implement the ZIP standard and as a result their support is limited to "store" and "DEFLATE" files. This partial implementation also affects some editing tools which normally support the PK3 format, such as (GZ) Doom Builder and SLADE.
MiniWikipediaLogoIcon.png7z
A .7z file used as the container for a ZDoom mod is usually given the .pk7, .pkz or .ipk7 extension, for similar reasons. This format offers a much better compression ratio, but it also increases the memory footprint on the engine, so caution must be taken when choosing between the 7z and ZIP format. A possibility would be to develop a mod as a ZIP file, then convert it to a 7z once finished, to decrease the size of the archive to be distributed. However, keep in mind that decompression is quite a bit slower than ZIP files, so loading times are increased, including during run-time when, for instance, new sounds are loaded.
Folders
Folders can be loaded directly by ZDoom, as if they were a ZIP or 7z file. This is most useful when creating a mod without using an editor such as SLADE, as it allows the creator to make changes to their mod with their own set of tools, and quickly load it into ZDoom.

Compressed archives have many advantages over (P)WADs, even for storing content for Doom:

  • Smaller file size due to compression.
  • Greatly reduced memory usage during play.
  • Proper use of directories instead of WAD namespaces.
  • You no longer need dedicated WAD management tools like XWE for manipulating your data.
  • More flexibility due to the ability to use full path names instead of 8-character ones in many systems.

How to

You can embed WADs inside archives. Any WAD file found in the root directory will be added to the lump directory as well. This allows loading many of the ZIPs distributed through /idgames without the need to extract them. If several wads are included in an archive, they will be loaded in alphabetical order.

WARNING: Loading WAD files inside of an archive will cause memory issues to arise. ZDoom will unpack each WAD file and use more memory to access the contents. This effect quickly adds up, especially in larger mods (with the exception of map wads in the maps/ folder, provided they follow the format explicitly -- see below). The bigger the mod is, the more likely it is on lower-end PCs that it may run out of memory during play and crashing ZDoom, or for memory corruption to occur. Thus, it is highly recommended to completely unpack the entire contents of any WADs inside, or part of the mod, into the sorted directories.
Furthermore, ZDoom supports and promotes sub-directories under the main ones for sorting purposes (i.e. sprites/Weapons/Cannon, sprites/Monsters/Technodemon, etc). No extra effort is needed to indicate the sprites are present, as ZDoom automatically scans all sub-directories.

Unlike WADs which do not have a true directory structure, the placement of data within archives is much more strictly enforced in order to allow the engine to recognize it as a default lump. Any special data must be placed in the respective directory inside the archive or it will not be found. For the lump name, the first 8 characters of the file name are used, the extension is stripped. So for example, to place a MAPINFO into an archive, you may name your file MAPINFO.txt, MAPINFO.lmp, or whatever extension you like, including none, and place it in the archive's root directory. The following sub-directories are used to assign data to the existing WAD namespaces in ZDoom:

Directory Description
acs/ contains ACS libraries normally found between A_START and A_END
colormaps/ contains Boom colormaps normally found between C_START and C_END. New ZDoom WADs should not need to use this.
filter/ contains lumps and directories that will only be loaded with specific games. See lump filtering.
flats/ contains flats normally found between FF_START and FF_END
graphics/ All special graphics like title pictures or font characters must go here. This namespace does not exist in WADs.
hires/ contains high-resolution textures normally found between HI_START and HI_END
maps/ contains levels in form of WADs. These WADs must only contain the data for one single level (including GL nodes lumps if required). Any other data in such a WAD will be ignored. Note that the file name and not the map label inside the WAD determines how the map is named in the game.
music/ contains all data that is used as music. This namespace does not exist in WADs.
patches/ contains patches normally found between PP_START and PP_END
sounds/ contains all sound files that are referenced by SNDINFO. This namespace does not exist in WADs.
sprites/ contains sprites normally found between S_START and S_END (also known as SS_START, SS_END)
textures/ contains textures normally found between TX_START and TX_END
voices/ contains Strife dialog sounds normally found between V_START and V_END
voxels/ contains voxel objects normally found between VX_START and VX_END
/ contains objects in the global namespace, such as MAPINFO and ZScript files

Tips

  • SLADE or similar programs are recommended for creating the actual archive file, to ensure programs like WinZIP or WinRAR do not create them with unsupported file compression. Otherwise, they may appear to be damaged, which may hinder modifications of the file with SLADE, Slumped, etc.
  • SLADE is also capable of editing many file types with special syntax highlighting similar to an integrated development environment, thus making it very useful for writing DECORATE and the like.
  • The archive file's directory is sorted alphabetically before adding it to the lump directory; any WAD files in the root are then loaded afterwards. Keep that in mind when creating data that relies on file name ordering. For most things, there is no need to depend on ordering, with the exception of texture animations of type range that animate textures from the flats/ or textures/ sub-directories.
  • Any file not in one of the reserved directories is not added to the WAD directory and can only be used by code that looks for full path names, which includes many things. The full extent of this is not listed here as it is often changing, so you will have to find which things support it yourself.
  • Sprite lumps for the \ frame in a WAD (such as VILE\* for one of the Arch-Vile's healing frames) can be put in an archive, the backslash character just has to be changed to a caret character (^). So, VILE^1 to VILE^8 in an archive will be interpreted as the VILE\1 to VILE\8 lumps. This replacement only works for sprites, any other lump name should not contain backslashes anywhere. As it is possible to use multiple sprite names for an actor with DECORATE, frames beyond Z need not be used however.
  • It is strongly recommended to use the .pk3, .pk7 or .pkz extension, not .zip or .7z, when creating a file meant to be loaded directly into ZDoom. The average user is used to opening a .zip file and extracting a .wad from it, so naming the actual game file a .zip will often cause unwanted confusion.
  • The contents of the files inside the archive must be identical to the lumps in a WAD. This is especially important for graphics. ZDoom does not read .BMP files! Even though that is the most likely format you will encounter, importing them with a WAD manager will convert them to Doom's internal format. XWE converts graphics encoded in Doom's internal format to .BMP during export. SLumpEd and SLADE can export these graphics as raw Doom lumps, and SLADE can also export them as PNG. In order for ZDoom to recognize graphics as such, they have to be either in Doom's internal format or a supported image format such as PNG.
  • Beware of hidden files! If you add a full directory or directory tree to an archive, it is possible that unwanted system files (such as Windows' thumbs.db file that tends to be created in any folder containing pictures) will be included as well. They will needlessly increase the file size and can trigger warning messages when loading ZDoom. Slumped frequently crashes when browsing through an archive's resources, as it expects thumbs.db to be a graphic and obtain incoherent values.

Compatibility

All modern editing tools are capable of handling raw folders and ZIP files, although none support 7z files so far.

Vavoom and Doomsday also use ZIP files for their resources; however their sub-directory organization differ. Adapting a mod from one of these ports to work in ZDoom may therefore require repackaging, in addition to conversion of enhanced features to their ZDoom equivalent. The Eternity Engine adopted a model mostly similar to ZDoom's, but different enough for incompatibility to be possible in both ways.

See also