Preview3MF

A macOS Quick Look extension for .3mf files (3D Manufacturing Format). Press Space on any .3mf file in Finder to see a 3D preview of the model — no slicer needed.

Features

• Quick Look integration — press Space in Finder to preview .3mf files
• 3D rendering with SceneKit — proper lighting, shading, and materials
• Build-plate grid — a world-fixed reference grid under the model, scaled to its footprint
• Auto-rotating model — spins around the vertical axis so you can see all sides
• Interactive controls — orbit and zoom with your mouse/trackpad in the preview
• Model info overlay — triangle count, object count, and dimensions parsed from the file
• Color support — renders per-object/per-triangle material colors when present
• Dark mode — preview and host app adapt to the system appearance
• Finder thumbnails — rendered icons for .3mf files, reusing the slicer's embedded preview when available
• Multi-object support — handles files with multiple mesh objects (Bambu Studio, PrusaSlicer, etc.)
• Drag-and-drop — drop .3mf files into the host app for inline preview

Installation

1. Download the latest release (or build from source)
2. Move Preview3MF.app to /Applications
3. Launch it once — this registers the Quick Look extensions
4. Go to System Settings → Privacy & Security → Extensions → Quick Look and make sure both are enabled:
   • PreviewExtension — the 3D preview shown when you press Space
   • ThumbnailExtension — the rendered icon shown in Finder
5. That's it — press Space on any .3mf file in Finder, or just look at the icons

Tip: If Quick Look doesn't pick it up immediately, run qlmanage -r in Terminal to reset the Quick Look cache.

Building from Source

Requires Xcode 15+ and macOS 13+.

git clone https://github.com/cavoco/Preview3MF.git
cd Preview3MF
xcodebuild -scheme Preview3MF -configuration Release build

Or open Preview3MF.xcodeproj in Xcode and hit Cmd+R.

How It Works

.3mf files are ZIP archives containing XML model data. The extension:

1. Extracts all .model files from the archive (using ZIPFoundation)
2. Parses <vertex>, <triangle>, <build> items, materials, and metadata from the XML
3. Builds SceneKit geometry with per-face normals for flat shading, applying each build item's transform
4. Renders with a 3-point lighting setup, a build-plate grid, and an auto-framed camera

For Finder thumbnails, slicers usually bake a rendered PNG into the package — the thumbnail extension reuses that embedded image as a fast path and only falls back to SceneKit rendering when none is present.

Project Structure

├── Preview3MF/              # Host app (SwiftUI)
│   ├── Preview3MFApp.swift
│   └── ContentView.swift    # Drag-and-drop preview UI
├── PreviewExtension/        # Quick Look preview extension (Space to preview)
│   ├── PreviewViewController.swift
│   └── Info.plist           # UTI + QL config
├── ThumbnailExtension/      # Quick Look thumbnail extension (Finder icons)
│   └── ThumbnailProvider.swift
└── Shared/                  # Used by all targets
    ├── ThreeMFParser.swift  # ZIP extraction, XML parsing, metadata, embedded thumbnails
    └── SceneBuilder.swift   # Mesh → SCNScene with lighting and build-plate grid

License

MIT