3DS is one of the
file format
A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free.
Some file form ...
s used by the
Autodesk 3ds Max 3D modeling, animation and rendering software.
It was the native file format of the
old Autodesk 3D Studio DOS (releases 1 to 4), which was popular until its successor (3D Studio MAX 1.0) replaced it in April 1996. Having been around since 1990 (when the first version of 3D Studio DOS was launched), it has grown to become a ''
de facto
''De facto'' ( ; , "in fact") describes practices that exist in reality, whether or not they are officially recognized by laws or other formal norms. It is commonly used to refer to what happens in practice, in contrast with '' de jure'' ("by l ...
'' industry standard for transferring models between 3D programs, or for storing models for 3D resource catalogs (along with
OBJ, which is more frequently used as a model archiving file format).
While the 3DS format aims to provide an import/export format, retaining only essential geometry, texture and lighting data, the related MAX format (now superseded by the PRJ format) also contains extra information specific to Autodesk 3ds Max, to allow a scene to be completely saved/loaded.
Structure
3ds is a
binary file format.
The format is
based in chunks, where each section of data is embedded in a block that contains a chunk identifier and the length of the data (to provide the location of the next main block), as well as the data itself. This allows parsers to skip chunks they don't recognize, and allows for extensions to the format.
The chunks form a hierarchical structure, similar to an xml
DOM tree. The first two bytes of the chunk are its ID. From that value the parser can identify the chunk and decide whether it will parse it or skip it. The next four bytes contain a
little-endian
In computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm
In mathematics
Mathematics is an area of knowledge th ...
integer that is the length of the chunk, including its data, the length of its sub-blocks and the 6-byte header. The next bytes are the chunk's data, followed by the sub-chunks, in a structure that may extend to several levels deep.
Below is a list of the most common IDs for chunks, represented in a hierarchical fashion depicting their dependencies:
The Labs: 3DS Specifics (now via Internet Archive)
/ref>
0x4D4D // Main Chunk
├─ 0x0002 // M3D Version
├─ 0x3D3D // 3D Editor Chunk
│ ├─ 0x4000 // Object Block
│ │ ├─ 0x4100 // Triangular Mesh
│ │ │ ├─ 0x4110 // Vertices List
│ │ │ ├─ 0x4120 // Faces Description
│ │ │ │ ├─ 0x4130 // Faces Material
│ │ │ │ └─ 0x4150 // Smoothing Group List
│ │ │ ├─ 0x4140 // Mapping Coordinates List
│ │ │ └─ 0x4160 // Local Coordinates System
│ │ ├─ 0x4600 // Light
│ │ │ └─ 0x4610 // Spotlight
│ │ └─ 0x4700 // Camera
│ └─ 0xAFFF // Material Block
│ ├─ 0xA000 // Material Name
│ ├─ 0xA010 // Ambient Color
│ ├─ 0xA020 // Diffuse Color
│ ├─ 0xA030 // Specular Color
│ ├─ 0xA200 // Texture Map 1
│ ├─ 0xA230 // Bump Map
│ └─ 0xA220 // Reflection Map
│ │ /* Sub Chunks For Each Map */
│ ├─ 0xA300 // Mapping Filename
│ └─ 0xA351 // Mapping Parameters
└─ 0xB000 // Keyframer Chunk
├─ 0xB002 // Mesh Information Block
├─ 0xB007 // Spot Light Information Block
└─ 0xB008 // Frames (Start and End)
├─ 0xB010 // Object Name
├─ 0xB013 // Object Pivot Point
├─ 0xB020 // Position Track
├─ 0xB021 // Rotation Track
├─ 0xB022 // Scale Track
└─ 0xB030 // Hierarchy Position
Shortcomings
It has been pointed out that, despite its popularity, the format may not be the most suitable for 3D data exchange. Some of the disadvantages mentioned are:
* All meshes must be made of triangles.
* All texture filenames are limited to the 8.3 DOS format.
* The number of vertices and polygons per mesh is limited to 65536.
* Accurate vertex normals cannot be stored in the .3ds file. Instead " smoothing groups"3DS MAX
Autodesk 3ds Max, formerly 3D Studio and 3D Studio Max, is a professional 3D computer graphics program for making 3D animations, models, games and images. It is developed and produced by Autodesk Media and Entertainment. It has modeling ca ...
, Lightwave and trueSpace still use smoothing groups, and Maya did up to v2.51).
* Object, light and camera names are limited to 10 characters. Material names are limited to 16 characters.
* Directional light sources are not supported.
Notes
[Smoothing groups (read about surfaces on Elements of Mesh Modeling for the rationale of their use) are stored as a bit field, with 4 bytes (a long int) for each face, thus allowing up to 32 (4×8) smoothing groups per face.]
References
External links
;web pages
3D Studio Mesh (3DS, PRJ) Files
— Autodesk Knowledge Network
3DS parsing tutorial
by Amir "Genjix" Taaki
Spacesimulator.net - 3ds format file reader, loader
by Damiano Vitulli
by Jeff Lewis. Link now via Internet Archive.
lib3ds: C library for loading/saving 3DS files
LGPL license
;text-file references
*
* (based on documentation by Jim Pitts)
* {{cite web
, title = 3D Studio File Format Information
, url = http://www.jalix.org/ressources/graphics/3DS/_unofficials/3ds-info.txt
, author = Jochen Wilhelmy
, date = 1997-06-08
, archiveurl = https://web.archive.org/web/20090404091233/http://www.jalix.org/ressources/graphics/3DS/_unofficials/3ds-info.txt
, archivedate = 2009-04-04
(based on documentation by Christophe Chabanois, Jim Pitts and Niklas Beisert)
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