JMF (Jackhammer Map Format)

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This page documents information about an engine not developed by Valve. This information is documented here because it has technical and/or historical relevance to Valve's engines.

The Jackhammer Map Format (JMF) is a binary file format used by J.A.C.K. to store map project data before being exported to MAP, like RMF. Unlike RMF, JMF supports objects being part of multiple visgroups, KVs longer than 15 characters, and Quake III patch meshes. Additionally, it can store paths in a slightly different manner, optimized for Jack's Path Tool.

Warning:As of the Christmas 2023 update, JMF files from the latest paid version of Jack cannot be opened in the free version of Jack. The latest free version saves files in JMF version 121, whereas the latest paid version is

Workaround:Using the paid version of Jack:

• If no KVs are longer than 15 characters:

Resave as RMF, then open the RMF.

If KVs are longer than 15 characters:

Resave as VMF or export to MAP.

• Open the JMF in a "Half-Life / TFC" game configuration, then resave as RMF or VMF.
• Export as MAP (Groups and VisGroups will be lost).

Confirm:It may be possible to create a program that strips the extra v122 information to create a v121 JMF, as the only new feature of the new version is background images for the 2D viewports.

See also

• MAP, used by the map compilers
• RMF, used by Hammer 3.x and openable by J.A.C.K.
• VMF, used by Hammer 4.x and openable by J.A.C.K.
• SMF, used by Sledge

External links

• Specification: JMF on THWL wiki
• JmfFormat.cs from MESS source code
• sledge-formats library