GLB and glTF are good at showing a model in a browser. They are poor at replacing the engineering file. A supplier who will machine, inspect or revise the part still needs STEP or the native CAD model.
GLB and glTF differ mainly in packaging: GLB is one binary file, glTF is a JSON scene that can point at extra buffers and images. Both are static meshes here. Neither is an editable CAD model.
Send glTF when the task is viewing
Use STEP to GLB or STEP to glTF when someone needs to rotate the shape, look at components or place the model in a web view. Inspect the result in the GLB viewer or the glTF viewer.
glTF coordinates are in metres. Check one known dimension after conversion. A model that looks right and is 1000 times off in scale is still the wrong deliverable.
A glTF that references .bin files or images must include those files. Remote URLs are not loaded. If textures are missing, the geometry may still be present; see missing glTF textures.
Keep STEP when the task is engineering
Choose STEP, not GLB, when the recipient needs any of these:
- a solid volume that is not a mesh estimate
- analytic faces and edges
- a file another CAD or CAM system will import as geometry
- a record of the design that can be compared with the next revision
A GLB made from STEP does not contain the feature tree, tolerances or the original surfaces. STEP versus a mesh is the same distinction: the mesh is a view of the shape, not the shape definition.
What not to promise
Do not describe a GLB as the manufacturing master, a lightweight STEP, or a file that can be converted back into the original CAD model. Mesh measurements are approximate. Mass still depends on a density the user chooses, and only after a usable volume exists.
Use a preview and engineering source from the same revision
A browser preview is most useful when it is deliberately paired with the engineering source instead of replacing it.
For a supplier review, name both files with the same part identifier and revision. State which file is the viewing aid and which file controls downstream engineering work. If a drawing is also included, make its revision equally explicit.
Before sending the package:
- reopen the STEP and the GLB/glTF output;
- compare one known overall dimension;
- confirm orientation and visible model scope;
- verify that the revision labels match;
- keep comments about appearance separate from comments about engineering requirements.
If the STEP and drawing are the manufacturing handoff, use the CNC RFQ checklist before treating the browser preview as evidence that the engineering package is complete.
A practical split
| Recipient needs | Send |
|---|---|
| Look at the model in a browser | GLB, or glTF with its local files |
| Machine, quote from solids, or edit the design | STEP, plus the drawing when the drawing controls the part |
| Both | STEP as the engineering file and GLB as the view, from the same revision |
Name the revision on both files. Two attractive views of different revisions are not a handoff.
Write a manifest for the viewing derivative
Keep a compact record with the source model revision, the GLB/glTF filename, the export date, known-size check and intended audience. If textures or buffers travel separately, list those local resources too. This record should let another person rebuild the preview without guessing which STEP it came from.
When a recipient says a model is incomplete, first ask which artifact they opened. A missing glTF buffer can remove mesh geometry, while unsupported texture display changes appearance. Neither symptom tells you that the engineering STEP lost a solid. Investigate the viewing package separately from the CAD source.
For a changed design, rebuild the derivative from the new released source and update the manifest. If only lighting or material presentation changes, label that as a preview update rather than an engineering revision. In both cases, retain the previous fixed review artifact when the project needs a record of what someone actually saw.
Do not place confidential models in a public example gallery merely because GLB is convenient to download. A display asset still exposes geometry and potentially component names. Public examples should use licensed public models or geometry you created and are permitted to publish.
Original article: CADProps · https://www.cadprops.com/guides/glb-gltf-for-cad-handoff/