What this is for. Everything else in Plumb measures on the calibrated plane —
the flat face you photographed. It cannot tell how far a cornice, sill or pier steps
out of that plane, and that off-plane depth is the largest silent error in
single-image metrology. This tool uses your phone's AR sensors to measure that depth
directly, so you can record it instead of guessing.
You do not need this for a normal capture. Skip it unless you are checking how far a
feature stands proud of the wall.
It takes over the whole screen. That is how WebXR works — Android hands the display
to the AR session, so Plumb's own controls disappear until you leave it. You are not stuck:
1 · Move the phone slowly so it finds surfaces.
2 · Tap a surface to drop a point. Tap a second point and Plumb reports the distance.
3 · Press the system Back gesture, or the × Android draws in the corner,
to come back here. Your points are kept.
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