How AR pattern tracing works

Sttchr is an AR sewing app. It uses your iPhone or iPad camera to find your fabric, lays the pattern on it at the size it was drafted, and holds it there while you chalk the lines. Here is what happens at each step.

1. Finding your fabric

Before it can place anything, the app has to understand the surface in front of it: where the fabric is, how far away, and at what angle. A single camera reads depth from movement, the way your eyes do when you shift your head. That is why the app asks you to move.

While it scans, it coaches you. Point at your fabric. Move left. Move left more. Step back a little. If the room is too dim it says Turn on a light. When it has the surface it says Found it! and places your pattern by itself.

Plain, dark or very smooth cloth gives the camera little to hold on to. If the search runs long, the app offers Cannot find them? Place it here, so you can drop the pattern yourself and carry on.

2. True size, every time

Every piece is drawn at its real printed size, read from the pattern file. A bodice front drafted at 42 cm is 42 cm on your table. There is no pinch to zoom, on purpose, because pinching would break that. Scale is a separate control that moves in tenths of a percent, and the app shows Not true size any time you leave 100%.

Each pattern carries a scale reference, a square or line of known length. Lay a ruler on it once on a new surface and you know the projection is right. See how to scale.

3. Staying put while you trace

Once placed, the pattern is anchored to the fabric, not to your screen. Walk around the table, lean in, step back, and it stays where you put it. If you move too fast the app says Slow down. If it loses its place, it tells you to point back at where you started so it can re-lock.

Tap Lock before you start chalking. It stops finger drags from moving the pattern, so a hand on the screen mid line cannot shift it.

4. Tracing a whole layout

A pattern is many pieces. When you move on to the next one, the last stays on the fabric as a faint ghost, so you can lay out the whole cutting plan piece by piece. At the end, Trace all shows every piece together, which is the fastest way to check a layout fits your yardage before you cut.

• Nested sizes. Tap a size to recolor it, so yours stands out from the lines around it.
• Mirrored pieces. Mirror flips a piece for the second side.
• Line color and weight. Pick a color that shows on your fabric, and go heavier if you are squinting.

More in tips and tricks for a cleaner trace and how to trace. Weighing AR against a projector? See projector vs AR sewing patterns.

Frequently asked questions

How accurate is AR pattern tracing?

Every piece is shown at the size it was drafted, and there is no pinch to zoom. Check it once against a ruler with the scale reference, and the app shows Not true size any time you leave 100%.

Does it work on any fabric?

Most fabric works. Plain cloth in a dim room is the hardest for a camera, so turn on a light and move the phone side to side. If it still cannot find the surface, place the pattern yourself.

Do I have to print anything?

No. Point your phone at the fabric and the app places the pattern for you. There is nothing to print, tape or calibrate.

Which devices does it run on?

Sttchr runs on iPhone and iPad. AR tracing needs the real camera, so it does not run in a simulator.

Will the pattern drift while I trace?

It is anchored to the fabric, not the screen. Move slowly and steadily. If the phone loses its place, point back at where you started and it re-locks.