What does unify normals do?

It flips triangle winding as needed so adjacent triangles traverse shared edges in opposite directions, then flips closed components with negative signed volume.

Does it change geometry?

No. Positions are unchanged; only the order of the three indices in a triangle can be swapped.

Why are some conflicts reported?

Non-manifold or non-orientable edge configurations cannot all be satisfied. The tool reports conflicting constraints and leaves those choices visible rather than hiding them.

Does unifying normals change the shape or dimensions?

No. It only reverses triangle winding where needed; vertex positions, bounds, and volume are unchanged.

Will this fix the slicer's inside-out or missing-layer error?

Often, yes: consistent outward winding helps slicers decide inside and outside. It cannot fix holes or self-intersections; run manifold-check afterward.

Mesh repair/Normals

Unify mesh normals (local)

Make triangle winding consistent across shared manifold edges and flip closed components to outward orientation. The Worker accepts STL, OBJ, PLY, 3MF, GLB, or self-contained glTF and writes an oriented binary STL locally.

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

Oriented mesh

No upload

Oriented mesh

Winding is propagated across shared manifold edges. Closed components are flipped to outward orientation using signed volume. Boundary and non-manifold edges cannot constrain their neighbours.

Drop a mesh to orient

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Shared manifold edges are used to make triangle winding consistent; output is binary STL.

.stl · .obj · .ply · .3mf · .glb · .gltf → STL

Drop a mesh to orient

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Shared manifold edges are used to make triangle winding consistent; output is binary STL.

Choose a file

Max file size: 500 MB · No upload

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

How it works

1
Drop a mesh file in any supported format.
2
The Worker builds shared-edge constraints between adjacent triangles and propagates a consistent winding.
3
Closed components whose signed volume is negative are flipped to point outward.
4
Download the oriented binary STL. No upload is performed.

What the numbers mean

Normals

Winding is propagated through shared manifold edges. Open boundaries and non-manifold edges cannot constrain their neighbours, so conflicts and non-manifold edges are reported instead of silently guessed.

Limits

This operation changes triangle order, not vertex positions. It does not fill holes, split non-manifold edges, or remove self-intersections; use clean-mesh, fill-holes, or a slicer check as needed.

Printing notes

Run manifold-check after orientation to confirm solid winding.
Open surfaces may be consistently wound but cannot have an outward closed orientation.
Keep the original file until a slicer accepts the oriented STL.

Questions

References

· ISO/ASTM 52900
· Mesh orientation and signed volume