Does this repair every self-intersection?

No. It merges separate closed shells that overlap. Self-intersections within one connected surface are not repaired and are rejected with an explanation.

Does it upload the model?

No. Parsing, component splitting, Manifold union and STL writing all run in the Worker; no file or result is uploaded.

What happens when the model is already a single clean shell?

The tool reports one component with zero self-intersections and writes the cleaned input unchanged, so you can still download it.

Why does it fail on an open mesh?

Every shell must be closed and consistently oriented before a Manifold union is meaningful. Use fill-holes, clean-mesh or repair-non-manifold first.

Why is the post-merge self-intersection value not computed?

The post-check uses the same 200,000-triangle cap. A larger merged result is still written, but the self-intersection verification is skipped.

Mesh repair/Topology

Merge overlapping shells (local)

Merge separate closed shells that overlap into one watertight STL locally. The Worker welds and validates the mesh, splits edge-connected shells, checks self-intersections and unions the shells with Manifold WASM without uploading the model.

ReadyNo uploadWorkerSTL · OBJ · PLY · 3MF · GLB · glTF

Tool facts

Formats: STL · OBJ · PLY · 3MF · GLB · glTF
Output: Mesh file
Worker: Yes
Max file: 500 MB
Runs: in your browser

Why local

Overlapping shell merge

No upload

Overlapping shell merge

This tool unions separate closed shells that overlap. It does not repair self-intersections inside one connected surface; use CAD or a voxel repair for that case.

Drop overlapping shells to merge

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Every shell must be closed and consistently oriented; separate overlapping shells are unioned into one STL. Limited to 200,000 triangles.

STL · OBJ · PLY · 3MF · GLB · glTF → STL

Drop overlapping shells to merge

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Every shell must be closed and consistently oriented; separate overlapping shells are unioned into one STL. Limited to 200,000 triangles.

Choose a file

Max file size: 500 MB · No upload

No upload · File.slice() / ArrayBuffer → Worker → merged STL.

How it works

1
Drop an STL, OBJ, PLY, 3MF, GLB, or self-contained glTF file.
2
The Worker welds vertices, removes degenerate/duplicate triangles and checks watertightness and winding.
3
Edge-connected shells are separated and each shell is validated as a closed, consistently oriented manifold.
4
A triangle-pair test reports self-intersections before merging.
5
Separate overlapping shells are unioned with Manifold WASM; the result is checked again for topology and self-intersections.
6
Download the merged binary STL. A single clean shell is written unchanged.

What the numbers mean

Method

The repair is a Boolean union of separate closed shells, not a voxel remesh or a general surface reconstruction. It resolves volume overlap between shells and removes the interior surfaces created by the overlap.

Components

Components are grouped by shared edges. Shells that touch only at a vertex are separate components. A single clean component needs no merge and is written unchanged.

Self-intersections

The triangle-pair detector reports self-intersections before and after the union. If the input is one connected surface with self-intersections, this tool rejects it because Manifold union cannot repair a single self-intersecting surface.

Limits

The operation is limited to 200,000 triangles and 500 MB input. Every component must be watertight and consistently oriented; otherwise repair it with clean-mesh, fill-holes or repair-non-manifold first.

Verification

Manifold produces the union from closed oriented shells. The result is checked for watertightness and solid winding; a large merged result above the self-intersection cap reports the post-check as not computed.

Printing notes

Use this when a model is built from overlapping closed parts, such as a keychain, enclosure, or imported assembly.
Run manifold-check before merging if the shell has open boundaries or wrong winding.
A merged model can still have thin walls or overhangs; run printability checks before slicing.
The output is binary STL; inspect it in the viewer or slicer after the merge.
For a single self-intersecting surface, repair the geometry in CAD or use a voxel-based tool; this tool will reject it.

Questions

References

· ISO/ASTM 52900
· Manifold geometry library
· Mesh self-intersection and overlapping shells