How to open a 3D file online
- Drop the file on the box above, or click Open a file. The viewer reads STEP and STP, IGES and IGS, STL, OBJ, 3MF, GLB, and glTF.
- For a .gltf file that keeps its geometry in a separate .bin file, select the .gltf and the .bin together.
- Drag to turn the part, and scroll or pinch to zoom. Click Fit to see the whole part again.
- Read the size, the volume, the surface area, and the mesh check beside the part. For an STL or an OBJ, check Units in the file first.
- Click Download STL to save the part as an STL in millimetres, or Download report for the figures.
The sample is a STEP file of an L-bracket with a fillet inside the bend and four 6.5 mm holes. The exact solid has a volume of 26.65 cm³. The viewer measures the triangle mesh it makes from the solid, so the viewer's figure differs slightly.
One set of facts for every format
Each format is turned into the same thing, a mesh of triangles in millimetres, and measured the same way. You get the bounding box, the volume, the surface area, the number of triangles and shells, and the same mesh check as the STL viewer. That way, a STEP file from one customer and an STL from another can be compared directly.
| Format | What the file stores | Unit | How the viewer reads the file |
|---|---|---|---|
| STEP, STP | Solids and surfaces, as text. The Library of Congress describes STEP-file as a plain-text exchange format for product data. | Stored in the file | The OpenCascade kernel covers the surfaces with triangles |
| IGES, IGS | Surfaces and curves | Stored in the file | The same kernel, face by face |
| STL | Triangles only (Library of Congress) | None | Read directly |
| OBJ | Polygons, and optionally free-form curves and surfaces (Library of Congress) | None | Polygons split into triangles |
| 3MF | Meshes, components, and build items in a ZIP package (3MF core specification) | Stored in the file | Every build item, with its transform |
| GLB, glTF | Scenes of meshes, materials, and animations (glTF 2.0 specification) | Metres | Scaled to millimetres and turned so Z is up |
How each format is read
STEP and IGES files hold exact surfaces, which have to be covered with triangles before anything can be measured. The viewer does that with occt-import-js, the OpenCascade geometry kernel compiled to WebAssembly, which runs in a background thread of this page. The kernel converts the file's own unit to millimetres. A curved face becomes many flat triangles, so a round hole in the mesh is a little smaller than the real one.
The glTF 2.0 specification says the units for all linear distances are metres, and defines +Y as up. CAD programs and slicers expect Z up, so the viewer multiplies every point by 1,000 and turns the part a quarter turn about X. A GLB is the binary form of glTF. The same specification describes a GLB as a container that stores the JSON, the buffers, and the images in one binary blob.
A 3MF names its unit, so the viewer converts the 3MF to millimetres. An STL or an OBJ has no unit, so the viewer reads millimetres until you choose another unit.
What the viewer leaves out
- Colours, materials, and textures. Only the shape is shown, in one colour.
- Compressed glTF. A file that uses Draco or meshopt compression stops with a message. Export the file again without mesh compression.
- Joins between IGES faces. If an IGES file stores its faces without the edges that join them into a solid, each face is covered with triangles separately. The mesh then has gaps along the joins, and the volume cannot be measured. Export the part as STEP instead.
- Native CAD files. SolidWorks, Inventor, Fusion, and Rhino files do not open here. Export the part from your CAD program as STEP.
- Very large files. The limit is 40 MB for STEP and IGES, and 150 MB for the mesh formats.
Your file is read in this browser and never uploaded. The page counts each use of the viewer, with the format and the triangle count, and never records the file, its name, or its measurements.
Quoting from the 3D file a customer sends
Customers send what their own software exports, so one request for quote can hold a STEP, an STL, and a 3MF. A STEP file is the one to machine from, because a STEP file keeps the real holes and radii. For more information, see the STEP file viewer and the guide to CNC quoting. For a printed part, the volume and the bounding box give the material and the machine.
ThriveAI builds quoting systems that read each request for quote and its models. Each system finds comparable parts you quoted before and prices new ones from your own rates. An estimator approves every quote before it goes out.