The 3D OBJ file format is a popular file format used in 3D modeling and computer graphics. It was originally developed by Wavefront Technologies for their Advanced Visualizer software, and has since become a standard for exchanging 3D model data between different 3D modeling and rendering programs.

The OBJ file format is a text-based format that stores 3D model data, including vertex positions, texture coordinates, vertex normals, and polygon definitions. This makes it easy to read and write OBJ files using a simple text editor, and also makes it easy to import and export OBJ files in a wide variety of 3D modeling and rendering software.

One of the key features of the OBJ file format is its support for both geometry and material properties. This means that an OBJ file not only stores the geometric data of a 3D model (such as the positions of its vertices and the definitions of its polygons), but also stores information about the materials and textures used on the model. This makes it a versatile and comprehensive file format for representing 3D models.

The structure of an OBJ file is relatively straightforward. It begins with a series of vertex data lines, each of which defines the position of a vertex in 3D space. This is followed by a series of texture coordinate data lines, which define how textures are mapped onto the model. Then, there are vertex normal data lines, which define the direction of the surface normals at each vertex. Finally, there are polygon data lines, which define the polygons that make up the model.

In addition to the basic geometry data, OBJ files can also include material libraries and references to external texture files, which allows models to be accurately rendered with their intended appearance in different 3D software applications. This makes the OBJ file format an excellent choice for sharing 3D models between different programs and for archiving 3D model data.

Overall, the 3D OBJ file format is a powerful and flexible format for representing 3D model data. Its text-based nature and support for both geometry and materials make it widely used and supported in the 3D modeling and rendering industry. Whether you are a 3D artist, game developer, or computer graphics enthusiast, understanding the 3D OBJ file format can be a valuable skill in your toolkit.