TruDepth

A native iOS app for real-time LiDAR depth visualization, 3D room scanning, and object measurement, built with ARKit, RealityKit, RoomPlan, Metal, ModelIO, and SwiftUI.

Features

Live Depth

• Real-time LiDAR mesh reconstruction rendered via ARKit + RealityKit
• Two visualization modes:
  • classify — semantic surface coloring (walls, floors, doors, windows)
  • depth — GPU-accelerated jet-colormap heatmap on black background via Metal
• Center-point distance readout sampled from the raw sceneDepth pixel buffer at 150ms intervals
• Metal heatmap uses a zero-copy CVMetalTextureCache path — no CPU roundtrips for the depth overlay

Scan Room

• Full 3D room capture via the RoomPlan framework, including walls, doors, windows, and furniture
• Real-time wall detection counter and progress indicator during scanning
• Depth snapshot: tap the capture button during a scan to save a jet-colormap PNG of the raw LiDAR depth data alongside the USDZ export
• Exports scans as USDZ — viewable in AR via QuickLook or shared directly from the app

Scan Item

• Object scanning using ARWorldTracking + LiDAR mesh reconstruction
• Keep the phone still and rotate the object — the app builds a 3D mesh in real time
• Live bounding box readout shows width × height × depth in centimetres as the mesh grows
• Exports the captured mesh as USDZ via ModelIO for sharing or AR viewing

Scan History

• Persistent scan library stored in the app's Documents directory (TruDepthScans/)
• Tracks both room scans and object scans with distinct icons
• Scan records keyed by filename for stability across reinstalls
• Optional depth PNG stored alongside room scan USDZ records
• Swipe to delete or share any previous scan
• 3D model viewer with full-bleed SceneKit rendering for any saved scan

Architecture

The app is structured across four source files plus one Metal shader:

File	Responsibility
AppDelegate.swift	App entry point, tab navigation, HomeView, ScanHistoryView, design system tokens
ViewController.swift	RoomScanView (RoomPlan session), ModelViewerView (SceneKit + QuickLook), ScanStore, ScanRecord
SceneDelegate.swift	LiveMeshView (ARKit session + mesh visualization), DepthHeatmapRenderer (Metal pipeline)
ObjectScanView.swift	ObjectScanView + ObjectScanViewModel (ARWorldTracking + LiDAR mesh + MDLAsset USDZ export)
DepthHeatmap.metal	Full-screen quad vertex shader + jet-colormap fragment shader for the depth heatmap

Key Design Decisions

• ScanRecord stores filename, not URL — the Documents directory path changes across reinstalls; the URL is recomputed at access time.
• ScanRecord has a scanType field with backward-compatible Codable decoding (decodeIfPresent, defaults to .room for old records).
• Phase enum has no associated values — CapturedRoom is not Equatable, so associated values broke phase comparison. Room data and URLs are separate @Published properties on the view model.
• Metal heatmap is a separate MTKView overlay — keeps the ARView render loop untouched; in depth mode a Color.black layer is inserted between the ARView and the MTKView so jet-color values pop against a dark background.
• Depth snapshot uses a post-scan ARSession — RoomPlan's session does not expose its underlying ARSession; after RoomCaptureSession.stop() a brief standalone ARSession with .sceneDepth semantics captures one frame.
• Object USDZ export uses ModelIO — ARMeshAnchor vertex positions are transformed to world space and packed into MDLMesh / MDLAsset, then exported via MDLAsset.export(to:).
• CVPixelBuffer cross-thread transfer — wrapped in UncheckedSendable with explicit CVPixelBufferLockBaseAddress/Unlock ownership.

Requirements

• Xcode 15 or later
• iOS 14.0 or later
• LiDAR-equipped device (iPhone 12 Pro or later, iPad Pro 2020 or later)
  • All core features require LiDAR; the app degrades gracefully on unsupported devices

Usage

1. Home — overview of features and recent scans. Tap any feature card to begin.
2. live depth — enter real-time LiDAR visualization. Use the segmented control to switch between classify and depth modes. The distance badge shows center-frame depth in real time.
3. scan room — walk around a room while RoomPlan builds a 3D model. Tap the aperture button to save a raw depth snapshot. Tap done when coverage is complete.
4. scan item — place an object on a flat surface, keep the phone still, and slowly rotate the object. The bounding box readout updates live. Tap done to export.
5. History tab — full list of saved room and object scans. Tap any row to open the 3D model viewer. Swipe left to delete, swipe right to share.

Contributing

PRs and issues are welcome. For significant changes, open an issue first to discuss the approach.