What the STL keeps, and what it loses
| In the STL | |
|---|---|
| Shape | Every triangle of every mesh, where the scene places it. A mesh drawn several times is there each time |
| Size | Millimeters, from the GLB's meters, or another unit you choose |
| Which way up | Standing on Z, as the model stands on screen |
| Names and the scene's tree | Lost: every mesh goes into one |
| Colors, materials, textures | Lost. A 3MF keeps each mesh as a part, with its color |
| Animations | Not played: the model as the viewer shows it, at rest |
| Lights, cameras, points and lines | Left out: they are not surfaces |
How to convert a GLB to STL
- Drop the GLB on this page, or choose it with the button. For a glTF, drop the
.gltfwith its.binand picture files, or a ZIP of its folder. - Look at the model and its size. The panel gives it in meters, as the file has it.
- Read the check: Watertight says whether the surface is closed, which a slicer needs.
- Choose Download STL. The file is named after the GLB, in millimeters: a model 0.08 m wide is 80 mm wide in the slicer.
A model made to be seen, not printed
GLB is the format of web pages, games and AR, and a model made for those only has to look right. It is often an open surface: a face with no back, a tree whose leaves are single planes, a character whose eyes are separate pieces sunk into the head. The check counts open edges and the holes they make, and draws them in red; volume is marked unreliable when the surface is not closed. The STL is saved as it is. STL repair closes holes and turns flipped faces; pieces that cross each other are left as they are.
A model may also be far smaller or larger than you mean to print it. The size is shown before you download. Scale it in the slicer, which keeps the proportions.
Size and orientation
glTF states both: meters, and Y up. Slicers expect millimeters and Z up and read an STL that way, since the STL itself states neither. The converter multiplies every number by 1,000 and turns the model a quarter turn about X, so that it stands on the bed as it stands in the viewer. If you need another unit, choose it under Unit of a saved STL, OBJ or PLY.
Several meshes, and several files
Every mesh of the scene goes into the STL, each where the scene puts it, and a mesh drawn many times over (an instanced fence, a row of seats) is there every time it is drawn. Several GLB files dropped together are saved together as one STL; hide any you want left out. Each stays a separate shell, which a slicer can split into objects. A scene of more than 12 million vertices, counting each mesh as often as it is drawn, is more than can be written as one mesh here, and the page says so when you save it; on its own it can still be saved as a glTF, which keeps it as it is.
STL, 3MF or OBJ
STL is read by every slicer. A 3MF keeps each mesh as a part, with its color, and states its unit, for a print in several colors. An OBJ keeps the names of the meshes and their colors for another 3D program. Both, and glTF and PLY, are saved from the links under the button.
Questions
Is my file uploaded?
No. The GLB is read and the STL is written by your own browser. Nothing is sent to a server.
Why is the STL the right size when other converters make it tiny?
A GLB is in meters, and a slicer reads an STL in millimeters. Copied across as they are, the numbers of a figure 0.12 m tall make a model 0.12 mm tall. This converter writes millimeters, so the figure is 120 mm tall in the slicer. Another unit can be chosen under Unit of a saved STL, OBJ or PLY.
Why does it stand the right way up?
glTF puts Y up, and slicers stand a model on Z. The model is turned so that what stands up in the viewer stands up on the print bed.
Are the colors and textures kept?
No. An STL holds only triangles. For a print in several colors, save a 3MF from the link under the button: each mesh becomes a part of one object, with its material's color, and a slicer lets you give each part its own filament. Textures are pictures laid over the surface, and no format a slicer reads keeps them as they are.
My model is animated. Which pose do I get?
The pose it stands in without the animation playing, as the viewer shows it. Animations are not played here.
Can I convert a glTF with its .bin file?
Yes. Drop the .gltf together with its .bin and pictures, or a ZIP of its folder. The page reads only the files you give it; nothing the file names is fetched from anywhere.
Why will my file not open?
A GLB compressed with Draco, or with KTX2 textures, is not read here yet: the page says which. Export it again without that compression and drop the new file.