OBJ File Format
The OBJ file format is a widely used standard for 3D graphics interchange, primarily utilized in the field of computer graphics to represent and exchange 3D geometry. Here is detailed information about the OBJ format:
Overview
The OBJ file format:
- Was developed by Wavefront Technologies for its Advanced Visualizer animation package.
- Is a simple data format that represents only the geometry of 3D objects, including vertices, faces, normals, and texture coordinates.
- Does not support animation, scene hierarchy, or material properties directly, though these can be linked through related files like MTL (Material Template Library).
Structure
The structure of an OBJ file includes:
- Vertices: Represented by the 'v' keyword, followed by x, y, z coordinates.
- Texture Coordinates: Defined with 'vt' followed by u, v, and optionally w values.
- Vertex Normals: Noted with 'vn' for normal vectors.
- Faces: Represented by 'f' followed by a list of vertices, texture coordinates, and normals, defining polygons.
- Objects and Groups: 'o' for objects and 'g' for groups to organize elements.
- Material Libraries: 'mtllib' to reference an MTL file for material definitions.
History and Evolution
- Introduced in the late 1980s by Wavefront Technologies as part of their animation software suite.
- Originally designed for their proprietary software but became a de facto standard due to its simplicity and compatibility with various 3D modeling and rendering software.
- Has seen little modification over the years, maintaining its basic structure, although extensions like PLY have been developed for more complex data.
Usage
Limitations
While versatile, OBJ has several limitations:
- Lack of support for complex features like animation, scene hierarchy, or dynamic properties.
- No standard for handling binary data, making files larger than other formats like FBX or Collada.
External Links
See Also