What is the 3D2 file format?
.3d2 is a 3D scene file format used by Atari Stereo CAD-3D 2.0, marketed as Cyber Studio - a 3D modelling and animation tool for the Atari ST developed by Tom Hudson and published by Antic Software. The files can contain up to 40 3D objects. Besides the actual object data, each file stores additional information such as colours and lighting settings for the scene.
How .3d2 differs from the earlier version
The .3d2 format is similar to the older .3D0 version; however, it is not based on the Motorola Fast Floating Point library (LIBF) used for storing object vertex coordinate data in CAD-3D 1.x. Each coordinate is stored as a 2-byte integer word, not as a 4-byte floating-point value, therefore keeping the file size compact. The byte order is big-endian, matching the Motorola 68000 CPU of the Atari ST.
.3d2 file structure
The .3d2 file is divided into two separate parts. The first part is a 256-byte header that holds information about lighting settings, the 16-colour Atari ST palette, and the number of objects in the file. The second part stores the per-object data structures that define the vertices, edges, and faces of each 3D object in the file.
CAD-3D 2.0 also supported LC Technology's StereoTek shutter glasses, enabling true stereoscopic 3D viewing on the Atari ST. The format is abandoned; 3D Object Converter for Windows retains limited import support.
Security & safety
RISK: LOWLegacy binary 3D data file with no executable content. Extremely unlikely to be weaponised; main risk is file corruption from bit rot on old media.
Format details
in a nutshellPrograms that open 3D2 files
Windows2 apps
quick3D
Free Open .3d2 directly in quick3D. Note: quick3D appears largely abandoned (site last updated ~2008); download with caution. 
3D Object Converter
Paid File → Open, select .3d2; can view and export to modern formats (OBJ, STL, etc.). Technical details
deep spec| Application | CAD-3D 2.0 (Cyber Studio) - Atari ST 3D modelling and animation software |
| Developer | Tom Hudson / Antic Software (Atari ST) |
| Original platform | Atari ST/STE/TT/Falcon (Motorola 68000 CPU) |
| Format type | Proprietary binary 3D scene/objects format |
| Byte order | Big-endian (Motorola 68000) |
| Coordinate data type | 2-byte signed integer per axis (not floating-point) |
| Difference from CAD-3D 1.x | CAD-3D 1.x used Motorola Fast Floating Point (LIBF) 4-byte values; 3D2 uses compact 2-byte integers, reducing file size |
| Maximum objects per file | 40 |
| File header | 256-byte fixed header containing lighting settings, 16-colour Atari ST palette, and object count |
| Colour depth | Atari ST 16-colour palette (4-bit) |
| Typical file size | 2 KB - 200 KB (depending on number and complexity of objects) |
| Stereoscopic support | Compatible with LC Technology StereoTek liquid-crystal shutter glasses for stereoscopic viewing |
| Current software support | 3D Object Converter (Windows); limited third-party import only |
| Released | 1987 (CAD-3D 2.0 / Cyber Studio, Atari ST) |
| Latest version | N/A (legacy format, no updates since late 1980s) |
| Specification | doudoroff.com |
3D2 conversions
Community Q&A
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