An OBJ in its own colours, not in grey.
An OBJ keeps its colours in a .mtl file and its pictures beside it. Open all of them together in your browser, nothing uploaded, to see the model in colour.
By Suraj Kumar4 min read
OBJ is one of the oldest 3D formats and still one of the most common. Its shapes are in the .obj file, but its colours are in a separate .mtl file, and its pictures in image files beside that. Open the .obj alone and you see a grey model. KeepSimp's OBJ viewer opens them together.
Choose every file at once.
Open the OBJ viewer and choose the .obj, the .mtl and the pictures together, or drop the whole folder's files at once. The page finds each file by the name the OBJ and MTL give it.
When the MTL or a picture is missing, the model still opens, and the page names exactly which file to add.
OBJ files have no unit.
An OBJ holds numbers without saying what they mean. The viewer reads them as metres, as most animation programs write them; choose millimetres, centimetres or inches if the size looks wrong.
Most OBJ files stand on Y, as the viewer expects. One from a CAD program may lie on its back: choose Z is up under More options.
Look at it, and measure it.
Turn it round, cut through it, list its parts and materials, and measure it. Its colours and shine are drawn as glTF draws materials, so a shiny MTL looks shiny.
OBJ has no animation; a model that moves needs GLB or FBX.
Further reading
Topics: open obj file · obj viewer · obj with textures · obj mtl file · obj file shows grey · obj viewer online
A little less theory. A little more doing.
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