CMOD File

What are CMOD files and how to open them

Are you having problems opening a CMOD file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CMOD files.

What is a CMOD file?

A .CMOD file is a Celestia 3D Model file.

Celestia's model format describes 3D geometry used by the Celestia universe viewer. It stores materials (surface appearance) and meshes (the shape) so that Celestia can render non-spherical objects with details such as textures, colors, and lighting effects. These files allow custom spacecraft, asteroids, satellites, and other objects to be visualized with their proper geometry and appearance.

The format is written by the Celestia software or by tools exporting to it (such as conversion utilities or plug-ins). It supports both a human-readable ASCII-text version and a binary version for faster loading. Version 1.5.0 and later added features including point sprites (tiny billboards for effects like nebulae), a "blend add" material attribute for additive blending, multiple texture maps (diffuse, normal, specular, emissive), and extended vertex attributes like tangent and multiple texture coordinates.

Internally an ASCII file begins with the header line "#celmodel__ascii" (binary version uses "#celmodel_binary"). The file then contains one or more material definitions (attributes like diffuse, specular, opacity, texture filenames), followed by one or more mesh definitions. A mesh includes descriptions of vertex attributes (position, normal, texture coordinates, colors, etc.), a pool of vertices, and primitive groups (collections of vertex indices) using types such as trilist, tristrip, trifan, linelist, linestrip, points or sprites.

How to open CMOD files

Important: Different programs may use files with the CMOD file extension for different purposes, so unless you are sure which format your CMOD file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 31, 2026

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