OBJ Viewer

An OBJ carries geometry only. Colours and images live in a second file, the MTL library, and in the texture files that library names. Select the whole group at once:

chair.obj
chair.mtl
textures/wood.png
textures/fabric.png

1. 1

   Select the group

   Drop the .obj, the .mtl and the textures together, or press Open 3D file(s) and choose all of them. A single selection is what makes the material references resolvable.

2. 2

   Look at what resolved

   The model is framed to fit as soon as it loads. A surface that stays uniformly grey usually means a reference did not resolve; Issues names the file when that is the cause.

3. 3

   Check the numbers, then save

   Overview and Materials describe the scene. Export PNG saves the current view if a picture is needed for a report or a message.

A browser never reveals the folder a dropped file came from: a folder arrives as a flat list of names. The MTL may say tex/wood.png while the dropped file is wood.png. Four matches are tried in order, and the first hit wins:

1. The exact path written in the file.
2. The same file name in any folder.
3. The exact path, ignoring upper and lower case.
4. The file name anywhere, ignoring case.

When two dropped files share a name, the viewer does not pick one at random. Issues lists both paths; opening the model again with a single file of that name resolves it.

References that point at another website are refused, and so are paths that climb out of the dropped set with ... A model resource is never fetched over the network.

A grey OBJ is almost always a file-name problem rather than a material problem. Three cases cover most of them:

• The MTL was not selected

  The OBJ names its library with mtllib chair.mtl. Without that file every usemtl name is unknown and the surface falls back to a neutral material.

• The material name does not match

  usemtl oak with a newmtl oak_wood entry is a different material. The used name is reported, so the mismatch is visible.

• The texture path is wrong

  map_Kd tex/wood.png has to match a dropped file under the rules above. A missing image leaves that map empty.

OBJ has no field for an up axis and no field for a unit. A part exported from a Z-up tool arrives on its back in a Y-up scene; press Z-up in the toolbar to stand it up. Dimensions that look 25.4 times off were written in inches.

The readout stays as the file contains it, and no scale is applied. A silent conversion would make the numbers disagree with the next program that opens the file, and that program is usually the one doing the slicing.

Overview counts meshes, vertices and triangles from the loaded scene and measures the bounding box before any fitting. Materials lists each material the library declared, its type and every texture slot with a thumbnail.

Faces with four or more corners are split into triangles by the loader, and the count is reported, so the triangle number is higher than the face count in the text file. That is a property of the file, not an error.

The three formats share geometry and differ in everything around it.

The STL viewer opens the geometry-only case, and the GLB viewer for single-file scenes covers the packed one.