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Getting started

What the app returns, how accounts work, and which frames you can load.

What it does

You give semper photos of a speckled surface before and during loading; it gives you back maps of how far every point moved and how much it stretched.

In DIC terms: one reference frame (undeformed) and several deformed frames (one per load step). It matches small windows called subsets on a grid and returns five maps per frame. New to this? Start with How DIC works.

Pipeline from reference and deformed frames to displacement and strain fields
Figure. Inputs on the left, matching on the phone, five output fields on the right.
Field Meaning Unit
U, V Horizontal / vertical displacement px
Exx, Eyy, Exy Normal and shear strain mε (millistrain)
Two things to know up front: displacements are in pixels — semper does not apply a mm scale, so convert with your own factor. And everything runs on the phone; optional cloud backup only stores the results you already computed, it never re-runs the analysis.

Getting in

Signing up is not enough — an admin has to approve your account before you can use the app.

In the app:

  1. Sign in with Google or email (password, or an emailed sign-in link).
  2. Email passwords need 8+ characters with upper and lower case, a digit, and a special character. Use Generate secure password if you want one filled in. Forgot password mails a link that reopens the app on a set-new-password form — you never leave the app to reset.
  3. After email sign-up, open the verification link, then sign in. Until you verify, sign-in is refused and a fresh link is sent each time you try.
  4. New accounts show Pending approval. Support is emailed automatically.
  5. Optional: tap Request access to add context in email.
  6. After an admin approves you, tap Check status. The screen does not refresh by itself.

Google and email-link sign-ins already prove the address, so they skip the password step.

Crash reports are opt-in. After the beta notice on first run the app asks once whether it may send crash diagnostics. Nothing is collected unless you say yes, and you can change your mind under Settings → Your data → Send crash reports. Reports never include your images or measurement results.

Auth, storage, and erasure: Privacy.

semper Home screen listing analyses with upload badges and add button
Figure. Home lists your analyses. Tap to open, long-press to select, pull down to sync, + to start a new one. Rows show upload state; newer builds also show restore progress or Only in cloud when local frames were freed.

If it fails: offline use is fine if this device was approved before — import and solve work without a network, and uploads wait until you are online. Still stuck on sign-in or approval? See Troubleshooting · signing in.

Images it accepts

Load a set of still photos, or a single video that semper samples into frames for you.

Rule If it fails
Every frame matches the reference pixel size Blocking error — you cannot run
At least one reference and one deformed frame Next stays off
At most Max frames (default 50) Extras are dropped, with a toast

Prefer PNG or TIFF. JPEG works but semper warns: compression damages the intensity gradients correlation needs.

RAW and DNG import only through Files, not Photos.

On import, semper measures your speckle. A weak pattern shows a low-texture warning and suggests a larger subset.

Starting from a video

Pick a video instead of photos and semper pulls the frames out for you — no need to export stills first.

When you choose a video, a sampling sheet opens: set the frame rate to sample at and the time segment to cover, and it shows a live estimate of how many frames you will get. The first frame becomes the reference, the rest become deformed frames in capture order.

The same Max frames cap applies (default 50) — if a segment would exceed it, the count is capped and the app notes it. Raise the limit in Settings → Analysis preferences if you need more.