The method, including the limits.
MeshMend performs conservative triangle-mesh operations. It does not infer the design intent or certify printability.
STL checks
Binary STL is recognized by its declared triangle count and exact byte length, even when its header begins with “solid”. ASCII STL must contain complete triangles. Non-finite coordinates, incomplete input and empty files are rejected.
Vertices with exactly equal coordinates are indexed together. Zero-area and duplicate faces are counted separately; topology diagnostics use the remaining unique, non-degenerate triangles. Open-edge counts are counts of edges, not counts of holes. Components are groups connected across edges shared by exactly two faces.
Repair operations
Cleanup removes duplicate and zero-area faces. Face winding is made consistent across ordinary shared edges. An isolated closed shell can be turned outward based on signed volume. Shells whose bounding boxes overlap retain their global orientation because they may represent cavities or intersecting objects.
Optional hole filling considers simple planar loops with 3–128 vertices, rejects intersecting boundaries and conservatively skips overlapping loop bounds. The maximum span is the XYZ bounding-box diagonal in millimeters. Planarity tolerance is the greater of one millionth of that span and 10⁻⁹ mm. A triangulation that duplicates existing faces or would attach to already closed edges is skipped.
The repair preserves exact vertex positions. It does not tolerance-weld nearby vertices, remesh, split arbitrary non-manifold structures, repair self-intersections or union overlapping solids. Hole filling adds faces and can close an intentional opening: inspect it before use.
3MF conversion
The primary package relationship selects the model. The converter follows printable build items, component transforms and supported production-extension references. Reflections preserve winding sign. Coordinates become millimeters. Required unsupported extensions, missing geometry, circular references and mixed model-part units are rejected.
All selected triangles can be exported together or a single build item can be selected. This is concatenation, not a boolean union. Colors, textures, material assignments, slicing profiles and plate metadata are discarded. No full 3MF conformance or slicer-vendor certification is claimed.
ZIP64 archives are not supported in this version. Standard archive directories and checksums are verified. Binary STL uses 32-bit coordinates; export is refused if rounding changes the measured mesh topology.
Resource limits
- 30 MiB input and 250,000 expanded triangles.
- Up to 256 build items, 2,048 archive entries and 10,000 visited object instances.
- 32 MiB per parsed XML part and 64 MiB of expanded relevant archive data.
- Bounded component nesting and a 30-second processing timeout, with cancellation.
- The issue overlay draws at most 20,000 edges; the report still counts the full supported mesh.
Validation and review
Independent fixtures cover topology, winding, holes, assembly transforms, units and malformed files. Downloaded STL geometry is checked by re-importing it. Browser checks are separate from algorithm checks. AI assisted the code and explanatory text; this version has not received independent mesh-engine or physical-print certification.
Version 0.1.0 · Documentation updated October 1, 2026.