Property Twin
An iPhone app that scans a home with LiDAR and turns it into a measured 3D twin you can open in any browser, and, as the product grows, the record of everything in it.
One twin, every stage of ownership
Property tools are fragmented. A realtor uses one platform for the listing, a buyer gets a PDF inspection report, a contractor works off photographs texted to them, and the homeowner ends up as the only thing holding it together — badly, from memory.
Property Twin is built on the premise that all of those people are looking at the same building, and should be looking at the same model of it. A property starts as a listing, becomes a workspace for contractors and inspectors, and ends up a living record for whoever owns it. Unlike 3D tour software, the twin is meant to live with the property rather than exist for the length of a sale.
The capture step has to be something anyone can do, so it is a phone a lot of people already carry: an iPhone Pro, walked through the house room by room, rather than a scanning rig or a hired photographer.
What works today
Scan a house in the iPhone app, one room after another. Apple's RoomPlan does the measuring on the phone, in real time, and coaches you while you scan. Walk up or down the stairs and the app ends that floor's pass and starts the next by itself. Upload, and the house comes back as a structured twin: rooms with their walls, doors, windows and openings, the stairs between floors, and the furniture and fixtures RoomPlan recognised, all with real dimensions.
Open it in any browser, on a phone, a tablet or a computer. Walk through it with game controls, name the floors, add the things the scanner cannot see and fix the ones it got wrong, keep track of upkeep, and print a plan.
It is measured, and honest about it: 2½ inches over a room 25 feet long, in a test against a tape measure. The scanner says when it is unsure of a wall, a door or a window, and the twin shows that, so you know what is worth scanning again. Good enough to plan with; check with a tape before you cut.
A scan is converted in the request that delivers it
A scan reaches the server as a small JSON document, and turning it into a twin is milliseconds of arithmetic, so the API does it inside the request that delivers it. There is no queue, no worker and no GPU. The conversion is pure code with no I/O, which is also what lets it be tested on a laptop with no phone in sight.
It started as video
Until the end of September 2026 the input was ordinary phone video, reconstructed on a home GPU with open research models. Every miss in two months of grading against a tape measure traced back to the same gap: a person with a camera gives no camera positions and no real-world scale, so both had to be estimated.
An iPhone Pro's LiDAR measures depth directly, ARKit tracks where the phone is, and RoomPlan turns the two into walls, doors, windows and furniture with real dimensions, on the phone, as you scan. The trade is a knowing one: Pro iPhones and iPads only, indoors only, and flat walls rather than a photoreal tour, which is what the twin was always going to draw.
- Phone
- An iPhone app in SwiftUI on Apple's RoomPlan and ARKit, for any iPhone or iPad with LiDAR
- Front end
- React and react-three-fiber, drawing the house as a translucent structural model
- Back end
- FastAPI and Postgres, converting each scan inside the request that delivers it
- Storage
- S3-compatible object storage, with models read from the browser through short-lived presigned links
- Verified by
- A scan format tested from both sides: the app's tests and the converter's read the same scan file
What's left
The layer the whole thing is for: documents, warranties and history anchored to the rooms and things they belong to, so the twin becomes a record rather than a model, and a way to hand a view of it to the people who work on the house.
It isn't deployed publicly, and there's nothing to sign up for yet. This page is the write-up.