General Information

In order to convert something, you first have to understand it. The Source Engine has its own file formats and structure.

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The Valve Developer Community Wiki has more in-depth explanations of each topic. Take a look at their website if you're interested.

Valve Pack

Valve PacK, also known as VPK, is a format used by most modern Source Engine games. It simply stores content.

Keep in mind that the format stores content across multiple files. The directory is stored in a specific file named [name]-dir.vpk and the actual content is stored in other files named [name]-[index].vpk.

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The index starts from 0 (like most programming languages).

MoDeL

MDL is Source's model format.

Additional data can be stored in PHY, ANI, VTX and VVD files.

VTF and VMT

The Source Engine defines Materials in VMT files, and those materials reference Textures that are stored in the VTF format.

BSP and VMF

The Hammer Editor stores map projects as VMF files (like a PSD) and the exported map has the BSP extension.