OBJ

OBJ is a file format, originally developed by Wavefront, that describes 3D geometry as plain text. Vertices, faces, texture (UV) coordinates and surface normals are written out line by line. Material information lives in a companion MTL file, which in turn points to the texture images.

Why OBJ is still everywhere

Its simplicity makes it dependable. The specification is short and well known, so nearly every modeling, sculpting, scanning and rendering program can read and write it. Furniture, accessory and decor models are often shared as OBJ, and when you need to move a model into an unfamiliar program, OBJ is usually the first thing to try.

That simplicity has a price. OBJ carries no animation, cameras, lights or object hierarchy. It stores no units either, so scale needs checking after import. On heavy scenes the file size grows quickly, since everything is written as text.

Practical tips

Keep the MTL file and the texture folder next to the OBJ, or the model will come in plain grey. Dense meshes from photogrammetry are often delivered as OBJ, and decimating them before they reach the render scene saves a lot of trouble. The checks in 3D modeling tips and tricks help keep exports clean as well.