meshfix-wasm

Client-side 3D mesh repair for the browser. Fixes broken STL, OBJ, and OFF files so they load cleanly in slicers like PrusaSlicer, Cura, and OrcaSlicer.

Built on PMP Library compiled to WebAssembly.

See it in action at www.justfixstl.com. All processing runs locally in the browser, no server, no uploads.

Install

npm install meshfix-wasm

Quick Start

import { MeshFixWorker } from "meshfix-wasm";

// Initialize (loads WASM in a Web Worker)
const meshfix = await MeshFixWorker.init();

// Load an STL file
const buffer = await fetch("model.stl").then((r) => r.arrayBuffer());

// Analyze
const { analysis, issues } = await meshfix.analyzeDetailed(buffer);
console.log(`${analysis.vertexCount} vertices, ${analysis.faceCount} faces`);
console.log(`Issues: ${issues.map((i) => i.message).join(", ") || "none"}`);

// One-click repair
const result = await meshfix.repair();
console.log(`Vertices: ${result.verticesBefore} → ${result.verticesAfter}`);
console.log(`Faces: ${result.facesBefore} → ${result.facesAfter}`);

// Export repaired mesh
const repaired = await meshfix.exportMesh("stl");
const blob = new Blob([repaired], { type: "application/octet-stream" });

// Clean up
meshfix.dispose();

API

MeshFixWorker (recommended)

Runs all processing in a Web Worker so the UI stays responsive.

const meshfix = await MeshFixWorker.init(options?);

Init options:

| Option | Type | Description | |--------|------|-------------| | workerUrl | string \| URL | Custom worker script URL | | coreUrl | string | Custom meshfix-core.js URL | | wasmUrl | string | Custom .wasm file URL |

Methods:

| Method | Returns | Description | |--------|---------|-------------| | analyze(buffer) | MeshStats | Basic geometry stats | | analyzeDetailed(buffer) | { analysis, issues } | Full topology analysis with issue detection | | repair(options?, onProgress?) | RepairResult | Auto-repair pipeline | | weldVertices(epsilon?) | WeldResult | Merge duplicate vertices | | removeDegenerates(minArea?) | RemoveDegeneratesResult | Remove zero-area and duplicate faces | | splitVertices() | SplitVerticesResult | Fix non-manifold (bowtie) vertices | | fillHoles(maxEdges?) | FillHolesResult | Fill boundary loops | | fixNormals() | FixNormalsResult | Orient normals outward | | reanalyze() | { analysis, issues } | Re-analyze after modifications | | exportMesh(format?) | ArrayBuffer | Export as "stl", "obj", or "off" | | toRenderData() | RenderData | Get vertex/index buffers for 3D rendering | | dispose() | void | Terminate worker and free memory |

MeshFix (main thread)

Same API as MeshFixWorker but synchronous. Useful for debugging or environments without Web Workers.

import { MeshFix } from "meshfix-wasm";
const meshfix = await MeshFix.init();

Repair Options

await meshfix.repair({
  weldEpsilon: 1e-6,   // vertex merge distance (default: 1e-6)
  minArea: 1e-10,       // degenerate face threshold (default: 1e-10)
  maxHoleEdges: 100,    // max hole size to fill (default: 100)
});

Repair Pipeline

The repair() method runs these steps in order:

1. Weld vertices — merge duplicates within epsilon distance
2. Remove degenerates — delete zero-area and duplicate faces (skipped if mesh is already watertight)
3. Split vertices — fix non-manifold (bowtie) vertices
4. Fill holes — close boundary loops with fan triangulation
5. Fix normals — orient all faces outward using signed volume

Progress Callbacks

await meshfix.repair({}, (event) => {
  console.log(`Step ${event.stepIndex + 1}/${event.totalSteps}: ${event.step}`);
});

Three.js Integration

const renderData = await meshfix.toRenderData();

const geometry = new THREE.BufferGeometry();
geometry.setAttribute("position", new THREE.BufferAttribute(renderData.positions, 3));
geometry.setAttribute("normal", new THREE.BufferAttribute(renderData.normals, 3));
geometry.setIndex(new THREE.BufferAttribute(renderData.indices, 1));

The renderData.faceFlags field contains per-face bitmask flags for issue visualization:

| Flag | Bit | Meaning | |------|-----|---------| | 0x01 | Degenerate | Zero-area face | | 0x02 | Duplicate | Identical to another face | | 0x04 | Flipped | Normal points inward | | 0x08 | Boundary | Face has an open edge | | 0x10 | Non-manifold | Adjacent to a non-manifold vertex |

Browser Support

Requires browsers with WebAssembly and Web Worker support:

• Chrome 57+
• Firefox 52+
• Safari 11+
• Edge 16+

Acknowledgments

This library uses PMP Library (MIT License) by the Polygon Mesh Processing Library developers and Computer Graphics Group, RWTH Aachen.

License

MIT