Free online GLTF to BREP converter

CAD applications that require boundary-representation geometry cannot edit a GLTF mesh as a native solid, so a mesh-to-BREP conversion is needed before import into tools such as FreeCAD or Open Cascade. The conversion is also useful for archiving a model as a BREP shell, but it does not reconstruct the original parametric CAD features.

What the GLTF format is

GLTF is a real-time 3D delivery format maintained by the Khronos Group. A .gltf file references JSON scene data, binary geometry, and usually external textures; a .glb file packages most or all of those resources into one binary file.

GLTF stores polygon meshes, transforms, materials, textures, cameras, animations, and sometimes skinning data. Blender, Autodesk 3ds Max, Maya, Unity, Unreal Engine, CAD viewers, game engines, and web applications commonly create or consume it. It is intended for display and interchange of triangulated or polygonal surfaces, not for editable CAD solids.

What the BREP format is

BREP, short for boundary representation, describes a model through topological entities such as vertices, edges, wires, faces, shells, and solids, together with the surfaces that define those faces. Open Cascade commonly uses BREP files with extensions such as .brep or .brp.

BREP is useful in CAD and engineering software because faces and topology can be selected, measured, checked, and used in boolean operations. It can preserve a closed shell as a solid, but a mesh conversion normally produces many planar triangular faces rather than cylinders, planes, fillets, or other analytic CAD surfaces.

How to actually convert GLTF to BREP

Using Blender and FreeCAD

1. Open Blender and choose File → Import → glTF 2.0. Select the .gltf or .glb file.
2. Inspect the scene and delete cameras, lights, armatures, and objects that should not enter the CAD model. Join separate mesh parts with Object → Join only when they should become one object.
3. Check the scale. GLTF conventionally uses meters, while STL has no embedded unit definition. Apply the intended scale with Object → Apply → Scale.
4. Export the selected geometry through File → Export → STL. Enable selection-only export and use binary STL unless an ASCII file is specifically required. Save it as model.stl.
5. Open FreeCAD and choose File → Open or File → Import for model.stl.
6. Switch to the Part workbench, select the imported mesh, and choose Part → Create shape from mesh. Set a sewing tolerance appropriate to the model; a value that is too small leaves disconnected edges, while a value that is too large can join nearby but unrelated edges.
7. If the resulting shape is closed, select it and use Part → Convert to solid when that command is available for the selected shell. Inspect the result in the tree and run the relevant geometry-check command before exporting.
8. Choose File → Export, select the BREP format, and save the result as model.brep. Export the shell instead if the mesh contains open boundaries and cannot form a solid.

Using an online converter

For a quick conversion without installing software, upload the GLTF file to the GLTF-to-BREP converter on 101convert.com and download the generated BREP file. Large scenes, external GLTF textures, animations, and non-manifold meshes may not convert as expected, so inspect the downloaded geometry in a CAD viewer.

Quality and compatibility limitations

This is usually a faceted mesh-to-BREP conversion, not a recovery of the source CAD model. Each triangle may become a separate planar BREP face, producing a large file and making later editing difficult. Curved surfaces remain faceted unless a reverse-engineering or surface-fitting tool rebuilds them.

GLTF materials, textures, animations, cameras, and lighting do not belong in a BREP model and are normally discarded. Verify orientation, normals, duplicate faces, self-intersections, holes, and non-manifold edges before attempting solid creation.

Check units after conversion because GLTF commonly represents meters while STL and BREP files may depend on the importing application's unit settings. If another CAD system must open the result, STEP is often a more interoperable exchange format than Open Cascade BREP; export STEP from FreeCAD after validating the solid.