Entspy is a program that lets you view and edit the entity properties of a compiled BSP map file (for Source Engine games such as HL2, CS:S and VtMB).
The program is useful for tweaking small entity properties (such as fog distance, etc.) without having to recompile a map. You can also use it to alter and add entities to the standard maps (such as increasing the number of spawnpoints).
I've written a small walkthrough showing how to add a spawnpoint to a map using Entspy.
A small update that allows version 20 BSP files (as used in the DoD:S release) to be loaded and saved.
A minor update that fixes a (rare) bug that could cause BSP file corruption (failing to terminate the entity lump correctly).
This update adds a "map info" menu item, which shows information about how the current map is stored on disk. It also adds some options to the map saving routine.
The Save BSP option will now ask if you wish to save the map entities in optimized format (which breaks the map checksum, but takes up the minimum space on disk), or in a non-optimized format (which wastes a certain amount of filespace, but preserves the map checksum).
Preserving the map checksum should prove useful to server owners who, e.g., wish to add spawnpoints to current maps. If the map is saved using the same name, it shouldn't need to be re-downloaded by clients who have the original map. This hasn't been tested, however.
You should use the optimized format if you are just tweaking your own map's entities, since it saves room.
If no message is shown on saving, the map file is already stored in a format that preserves the checksum.
Entspy can be downloaded here. It is a Java program, and requires the Java Runtime Environment 1.5.0 (download) or to run. (Note: If you've already installed the Java Runtime Environment 1.5.0 for use with VMEX, you don't need to download and installed the JRE again).