Partial conversion

A partial conversion is a PWAD that replaces a portion of the resources of the original game's IWAD. In contrast to a total conversion, the partial retains enough visuals, sounds, and gameplay mechanics to be considered a variant of the original, not a separate game.

There are two prominent types of partial conversions: gameplay mods and maps with custom resources.

Gameplay mods alter some portion of the gameplay. Many of these have been created for classic Doom, replacing the weapons or monsters or specific gameplay mechanics. Some of them add entirely new functionality, such as a flashlight or footstep sounds. Thus players of mod-friendly source ports, like GZDoom, often use multiple gameplay mods together.

Any fan-made map that uses custom resources, such as OTEX or cc4-tex texture replacements, is considered a partial conversion. Some maps also have other replacements, such as custom weapons or monsters.

A good example is the Valiant mapset, which has been released with two different versions. Both are partial conversions because they use cc4-tex and other custom textures. The first version of the mapset also has several custom weapons and mosters. After finalizing this, the creator wanted to play the maps in GZDoom with separate gameplay mods that replace all of the weapons and monsters. Since this would clash with his own cutomizations, he decided to make a second version of Valiant with only the custom textures.