OBJ (Wavefront)

The OBJ file format is a plain text 3D graphics format created in the 1980's as a means to describe complex 3D models and scenes in a human-readable format. The format was originally crafted by Wavefront Technologies as the primary file format used by their animation software at the time.

Although Wavefront created the format, it has since been updated and enhanced to suit the needs of other 3D modeling software. OBJ files have become a standard format within the 3D modeling industry, with most software applications able to read and write to the format.

OBJ files contain human-readable 3D model data. This can be as simple as the vertices and faces of a basic 3D shape. For example, here is the OBJ source code for a pyramid shape object:

In the example above, you can see we have defined 5 vertices and 6 triangles to create a water-tight 3D model of a pyramid. This is a fairly simplistic model; however, you will find more complex OBJ files that may contain thousands, if not millions, of vertices and faces.

In addition to the vertex and face data, an OBJ file can also include information about texture coordinates, normals, and material properties. Texture coordinates define how a 2D texture image, such as a PNG or JPG file, is mapped onto the model's surface, allowing for realistic surface rendering. Normals specify the direction that a surface is facing, which affects the way light interacts with the model. Material properties define the visual appearance of the model, such as its color, reflectivity, and transparency.

Summary

An OBJ file is a plain text file format that stores 3D geometric model data. It contains information about vertices, polygons, texture coordinates, normals, and material properties. It is widely used and compatible with many 3D software applications, though its text-based format can lead to large file sizes for complex models.