What is the RND file format?
An .rnd file is a rendering output file created by AutoShade, Autodesk's first standalone 3D rendering add-on for AutoCAD. AutoShade took 3D face objects defined in AutoCAD and produced shaded renderings saved as .rnd files, adding color and shading to images that AutoCAD itself displayed only as wireframes.
AutoShade 1 (released 1987) stored renderings as 2D vector data. AutoShade 2 (circa 1990) added Gouraud-shaded raster output at typical DOS-era screen resolutions - usually 640×480 or 800×600 - with up to 256 colors. Autodesk's 3D Studio for DOS (1990) superseded AutoShade entirely, and no modern software can natively open .rnd files.
The .rnd extension is also used by unrelated software - most notably by PGP and OpenSSL/PuTTY as a random seed file that stores entropy for cryptographic key generation. These random-seed .rnd files are entirely different in structure and purpose from AutoShade renderings, and are managed automatically by their respective applications.
Security & safety
RISK: LOWAutoShade RND files: passive binary data, no executable content. PGP/PuTTY .rnd random seed files: safe system files - deleting them forces the software to regenerate entropy; do not share them (they contain entropy used for key generation).
Format details
in a nutshell- PGP Random Seed File - PGP and OpenPGP tools (including GnuPG) use .rnd to store random number entropy data for key generation; plain binary data, not a rendering.
- PuTTY / OpenSSL Random Seed - PuTTY SSH client creates a .rnd random seed file (via OpenSSL RNG) typically in the user's home directory; unrelated to CAD.
Programs that open RND files
Windows1 app
AutoCAD (legacy, historical reference only)
Paid Modern AutoCAD (2024+) does NOT open .rnd files. No current software supports this format. AutoShade itself (DOS app) is the only known tool, and it is unobtainable. Technical details
deep spec| Internal format | Proprietary Autodesk binary (no standard wrapper or published specification) |
| Byte order | Little-endian (DOS/x86) |
| Compression | None (uncompressed raster or vector data) |
| Magic bytes | Undocumented - format has no publicly available specification |
| Color depth | Up to 256 colors (VGA-era display adapters) |
| Typical dimensions | 640×480 or 800×600 (DOS VGA/EGA resolution era) |
| Typical file size | Under 1 MB (typical 1980s-1990s screen-resolution renders) |
| Format variants | AutoShade 1 (2D vector output, 1987); AutoShade 2 (Gouraud-shaded raster, circa 1990) |
| Platform | MS-DOS; no modern software can open .rnd files natively |
| Superseded by | 3D Studio for DOS (1990); AutoShade was discontinued upon 3D Studio's release |
| Extension ambiguity | .rnd is also used by PGP and OpenSSL/PuTTY as a random entropy seed file - entirely unrelated format |
| Released | 1987 (AutoShade 1.0 for AutoCAD) |
| Latest version | AutoShade 2 / Release 2 (circa 1990; product discontinued) |
Community Q&A
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