OBJFormat

OBJFormat, commonly referred to as the Wavefront OBJ format, is a plain-text file format used to describe 3D geometry for interchange between graphics software. Originating from Wavefront Technologies in the 1980s, it provides a simple, human-readable representation of vertices, texture coordinates, vertex normals, and polygonal faces. An OBJFormat file consists of a series of lines, each starting with an identifier such as v, vt, vn, vp, f, g, o, or usemtl. Vertex lines define positions as v x y z; texture coordinates as vt u [v] [w]; and vertex normals as vn x y z. Faces are defined with f lines that reference vertex indices and may optionally include texture and normal indices in the form v1/vt1/vn1 v2/vt2/vn2 ... The format supports multiple objects and groups via o and g, and materials through mtllib and usemtl, with materials defined in a separate MTL file. Smoothing groups can be indicated with s.

OBJFormat favors simplicity and broad compatibility, making it a common interchange format for 3D models. It does not embed scene graphs, animations, or complex shading information within the file; these aspects are typically handled separately or in accompanying material files. Extensions and variants exist to accommodate additional data, but the core is widely stable. The .obj extension is usually paired with .mtl material files, which describe surface properties such as ambient, diffuse, and specular reflectivity and texture maps.