(October 3, 2017)
J.A.C.K. aims to be the universal level editor for Quake-based games, supporting Quake, its sequels, and games using the GoldSrc engine. Though based on older versions of Worldcraft, it aims to improve the formula with 64-bit support and smaller but incredibly convenient features that have been noticeably absent in other editors of its ilk.
Some of J.A.C.K.'s more useful features include brush merging, triangulation (the splitting of invalid brushes created through vertex manipulation into triangles), incremental saving in the same vein as 3ds Max, support for Linux, support for external model viewers, embedded plugin and shader support for Quake III: Arena, and the ability to load models and sprites from game archives. Simply put, J.A.C.K. is the power user's level editor.
J.A.C.K. has the ability to store levels in the normal MAP and RMF files customary to Quake-based editors, though it also supports its own editor format, JMF. JMF has some unique features over RMF, notably the ability to sort an object into multiple VisGroups. Levels can be both imported and exported in any one of the three formats. VMF files (Hammer 4.0's format for storing uncompiled levels) are supported on a limited basis—for example, no support for displacements.