Projection mapping with a phone
let the light do the measuring
Projection mapping with a phone means you stop drawing shapes by hand. You prop your phone beside the projector, the projector shows a series of stripes, and from what the camera sees Prism Mapper works out where every projector pixel lands. Over a cable it takes about half a minute. Then you click the objects you want to light.
What the phone scan actually does
Each stripe pattern splits the projector’s picture into light and dark bands: halves first, then quarters, then eighths, down to stripes a few pixels wide. Upright stripes first, then lying ones.
Pick one point on a box. In each pattern that point is either lit or dark, and those answers in order spell out a number: the column and row of the projector pixel that lights it. After about forty patterns, Prism knows for every point the phone can see which projector pixel falls on it. The stripes bend round your objects, and that bending is the shape of your room.
From that map it finds flat faces, curved surfaces and edges, draws each surface as a clean shape, and an object finder running on your computer separates the things in front of the projector. Every pattern comes with its opposite, so even dark or shiny surfaces can be read, and white frames along the way check that the phone has not moved.
Connect your phone in a minute
Nothing to install on the phone. It works with an iPhone in Safari or an Android phone in Chrome.
- 01
Open the projector window first
In Setup, click Open window on the projector card and make it fullscreen on the projector. Then click Next: pair phone.
- 02
Scan the QR code
Point the phone’s camera app at the QR code on the laptop and tap the link. No QR reader? Open the address shown under the code and type the six-character room code.
- 03
Start the camera
On the phone, tap Start camera and allow camera access. The laptop says Phone connected. Click Next: scan.
What a good scan needs
Most failed scans come down to light, movement or framing.
- A dim room
- Lights off or low, curtains closed. The projector must be the brightest thing the camera sees; daylight washes the stripes out. Keep the light steady, with nobody walking through the beam.
- A phone that cannot move
- A small tripod with a phone clamp is ideal; a stack of books works. Start the scan from the laptop so your hands stay off the phone.
- Right beside the lens
- From next to the lens the phone sees what the projector lights at almost the same angle, so shadows and hidden corners match.
- The normal 1× camera, turned sideways
- No zoom and no wide 0.5× lens. Hold it sideways for a wide projection, and keep that orientation: if the screen rotates mid-scan, the scan stops.
- The whole projection in view
- Leave a gap between the projection and every edge of the camera picture. Step back or turn the phone until the lime outline clears the edges.
- Screen awake, page in front
- If the phone locks or you switch apps, the camera pauses and the scan stops. Tap Keep screen on, or turn Auto-Lock off while you scan.
- A cable if you can
- Over HDMI the scan takes about 30 seconds. Over a wireless projector link it waits for each picture and takes about two minutes. You can scan on the cable and show over Wi-Fi afterwards.
Scanning and choosing what to map
- 01
Watch the four checks
The projector blinks while the phone finds it. On the laptop, wait for Phone connected, Projection found, Whole projection in view and Phone steady to tick.
- 02
Start, then hands off
Click Start scan on the laptop. The projector flashes black, white and stripes. If some areas came out unclear, the phone looks at just those again.
- 03
Read the heatmap
Green means full precision, yellow partial, red weak, grey unlit. Nearly all green is a clean scan. The first scan downloads the object finder once (about 450 MB).
- 04
Click what you want to light
Prism shows the phone’s photo with the objects it found outlined; the projector draws the same outlines on the real things. Click to add or leave out, then Map. Details in What do you want to map?.
When a scan will not cooperate
You never depend on the scan. Every route below works without it, or alongside it.
Click it in yourself
If the scan singles out nothing, click the objects on the photo to add them, or drag a box round one.
Draw by hand
Start a project with Draw by hand and drag a quad’s corners onto each surface. Quick for one wall or a few boxes.
Place it as a 3D object
Add a box, plane, pyramid or wedge and pin its corners to the real ones. If you scanned, dragged corners snap to scanned corners.
Scan again
Lower the lights, move the phone closer to the lens, use the cable. Rescan whenever the projector, the objects or the lens zoom move.
What leaves your phone
The live camera picture stays on the phone. Only the finished scan, with one photo of the scene, travels through the Prism server to your laptop. The server keeps scans for a limited time; a scan saved in your project stays in your browser until you remove it. The data and AI page has the details.
Phones only allow the camera on secure https:// pages, so the QR code always opens a secure address. On the free plan, a scan keeps every surface it finds; only shapes you add by hand count towards the four-shape limit.
Can I do projection mapping with just a phone?
The phone is the scanning camera, not the projector or the studio. You still need a projector and a laptop running Prism Mapper in Chrome or Edge; the phone measures the room so you do not have to draw the shapes.
Which phones work for the scan?
An iPhone with Safari or an Android phone with Chrome. There is nothing to install: the phone opens a camera page from a QR code.
Why does my scan keep stopping?
Usually the phone moved, its screen turned off, or it rotated. Prop it firmly, keep the screen awake, keep one orientation and start the scan from the laptop. The phone tells you why it stopped.
How long does a phone scan take?
About 30 seconds over HDMI and about two minutes with a wireless projector link. Finding objects afterwards takes 15 to 30 seconds, plus a one-off download of about 450 MB the first time.
Do I need to scan again if I move something?
Yes, if the projector, the objects or the lens zoom and focus move. For a small knock of the projector, Advanced mode can also align the whole scene by dragging four corners.
Let your phone measure the room
Open Prism Mapper on your laptop, connect the projector, and pair your phone from the QR code.
Start creating free