MaskFit

An iPhone app that measures your face with the Face ID (TrueDepth) camera and tells you how much to scale a 3D-printable mask, such as one from MakerWorld, in Bambu Studio.

Early prototype.

How it works

1. Sweep scan. You turn your head slowly in a circle while a Face ID-style ring fills in. Each TrueDepth depth map (640×480, about 15 per second) is snapped onto ARKit's face mesh by rigid ICP, because ARKit's head pose is a few millimetres and degrees off, differently at each angle. The frames are then merged into a 1.5 mm point cloud, which is drawn live on your face.

2. Measurements. Five distances are found on the merged cloud, using standard anthropometric landmarks:

   	Measurement	On the face
   A	Eye spacing	Eyeball centre to eyeball centre
   B	Face width	Across the cheekbones (zygion)
   C	Face length	Nose bridge (sellion) to chin (menton)
   D	Nose length	Nose bridge to nose tip (pronasale)
   E	Nose depth	Nose tip in front of the cheeks

   The scan ends once every value has settled (six estimates over 3 s within 0.6 mm).

3. Sizing. You pick the mask type and padding, then measure the same distance on the inside of the mask in Bambu Studio, and the app works out the scale percentage, including padding. It also flags masks made for different face proportions, nose clearance problems, and magnet and strap holes that will change size.

Layout

Path	What it is
MaskFit/FaceMeasurer.swift	Landmark geometry; pure Swift
MaskFit/DepthFusion.swift	Depth back-projection, point cloud, ICP registration; pure Swift
MaskFit/SweepScanner.swift	ARKit session, progress ring, live cloud
MaskFit/MaskSizing.swift	Scale advice: padding, check measurements, warnings; pure Swift
MaskFit/ResultsView.swift	Results screen with the lettered head and mask renders
MaskFit/Capture.swift	Development recorder that saves raw frames for replay on the Mac (remove before release)
Check/	Mac checks for the maths above, against a CC0 head with known measurements
Tools/	Blender scripts that make the test head data and the diagram renders
web/	Web page that measures a mask's STL or 3MF and downloads it scaled; mask.js is the geometry, check.mjs its check
MaskFitClip target	App Clip version; needs a paid Apple developer team

Build and run

You need Xcode 27 and an iPhone with Face ID; face tracking doesn't run in the Simulator.

1. Open MaskFit.xcodeproj, choose your team under Signing & Capabilities for the MaskFit target, and run.

2. From the command line instead (replace the device ID):

   xcodebuild -project MaskFit.xcodeproj -scheme MaskFit -configuration Release \
     -destination "id=<device UDID>" -allowProvisioningUpdates -allowProvisioningDeviceRegistration build

The App Clip isn't embedded in the app at the moment, because free Personal Teams can't sign App Clips.

To see the results screen without scanning, for example in the Simulator, launch with -demoResults. Add -demoScroll sizing, measure or tips to open it scrolled to that section with sample mask measurements.

Checks

swiftc -O MaskFit/FaceMeasurer.swift MaskFit/DepthFusion.swift MaskFit/MaskSizing.swift Check/main.swift -o /tmp/facecheck && /tmp/facecheck Check

This checks the landmarks on the test head and the fusion of synthetic depth maps rendered from 11 angles, both within 3 mm. It also checks detection of mirrored depth maps and the mask-sizing advice.

Pass a folder of frames recorded on the phone (Documents/capture, copied off with xcrun devicectl device copy from) to replay a real scan instead.

The test head is the realistic head from Blender's Human Base Meshes bundle (CC0).

Web: size a mask from its STL or 3MF

The web page loads a mask's STL or 3MF and finds A–E on its inside. A 3MF is measured as it sits on the plate, so any scale already set in Bambu Studio counts. The page uses the object with the most triangles and skips Bambu's modifier and negative parts. Downloads are STL. It does that with the same landmark rules FaceMeasurer.swift uses on the face, because the inside of a mask is a negative of a face. It then shows the lines on the mask, works out the scale with the MaskSizing.swift rules, and downloads the STL scaled. Everything runs in the browser and the file isn't uploaded. To get your measurements in, tap Copy measurements in the app and paste on the page, or open it with #a=64.3&b=144.5&….

python3 -m http.server 8765 --bind 127.0.0.1 --directory web

Then open http://localhost:8765. The check builds a mask from the test head (padded 4 mm, eye holes cut, turned and shrunk to 80%) and expects to get the head's measurements back:

node web/check.mjs

node web/check.mjs mask.stl (or mask.3mf) prints what it finds on any mask. web/mask.js ports the sizing rules from MaskSizing.swift, so a change to one needs the same change in the other.

Licence

MaskFit is free for non-commercial use under the PolyForm Noncommercial License 1.0.0. You can use it, change it and share your changes for any non-commercial purpose, as long as you keep the Required Notice line that credits the author. Commercial use isn't allowed. For a commercial licence, contact @talic.