Compiling a map is the process of turning a
map file used by an editor (usually a .map, .rmf, or .jmf file) into a file that can be run by the game itself (a .bsp file).
The compilation process runs through four programs known as compile tools. These are, in order,
CSG,
BSP,
VIS and
RAD. Each are responsible for a different set of tasks, and the next tool relies on and builds upon the previous tools. Compile tools are typically distributed and run as a full set. Editors and batch compilers usually offer a range of advanced options for each tool.
In order to get the best results (and run into the fewest issues) with mapping, it is always a good idea to use the most up-to-date compile tools for the target game engine. For
GoldSrc,
Zoner's Half-Life Tools (
ZHLT) were for many years the compilers of choice for most mappers, before
Vlucazn's Half-Life Tools (
VHLT) came with many further improvements and they are currently the tools most commonly recommended. For Svengine (Sven-Coop's branch of GoldSrc), you need to use the one that comes with its SDK in order to support the increased map size limit. The same applies to other game engine branches.
J.A.C.K.'s free version comes with a slightly outdated version of VHLT.
See also