Why don't you just make the app $2.99 up front? Why the annoying IAP?
TL;DR: Apple doesn't allow this yet.

I absolutely agree with you — I wish I could make it $2.99 up front (it would save me a lot of time), but Apple wouldn't approve the app.

The situation is like this: a developer can restrict an app for devices that support certain features (i.e. a developer can make an app available only for devices that support ARKit). My original intent was to restrict the app only for devices with the TrueDepth camera (currently iPhone X, XR, XS and XS Max) and without the useless camera part, but it turns out Apple won't let you do this (I've filled bug reports together with other developer and suggested that Apple let us, developers, restrict apps for TrueDepth camera-only devices).

So if you submit an app that is fully working only on the iPhone X and not on other devices, your app gets rejected. This is the reason why I made the app free with the useless camera part that's available on all devices and included the 3D Scanner part as an IAP that can be bought only on iPhone X (i.e. on devices with the TrueDepth camera).

Because the app can be dowloaded on non-iPhone X devices (again, no way to restrict it to iPhone X), I thought it'd be silly to ask $2.99 for an app that just takes photos on devices other than iPhone X — i.e. I didn't want to disappoint non-iPhone X users.

[new] What is Infinite Scanning and how to enable it?

Infinite Scanning is experimental feature that lets you scan (theoretically) infinitely large spaces — with this feature enabled, you're no longer limited to ~800MB scan sizes — the only limitation is your free storage on device!

To enable this feature, go to the iOS Settings app > Heges and turn on Infinite Scanning

Please note that this feature requires significant computational power, therefore it is advised that you scan slowly and if possible use the newer devices with Apple's A12 chip and newer (iPhone XS, XR, iPad Pro 2018 with FaceID). This feature works perfectly OK on older devices though (i.e. on iPhone X).

[new] How to Share Screen with another device?
You'll need:
  • Device A: an iPhone/iPad Pro with the TrueDepth camera (FaceID) - this device will be sharing its screen while scanning
  • Device B: arbitrary (even old, no need to have TrueDepth camera on this device) iPhone/iPad that you're able to install Heges on (no need to buy the IAP here) - this device will receive the shared screen from Device A
How to share screen:
  1. Enable Wi-Fi on both devices. You do not need to be connected to the same Wi-Fi - no need to be connected at all, just enable Wi-Fi.
  2. Double-tap the live video preview on both devices and an overlay will show up.
  3. Tap the "Start Sharing Screen" button on Device A.
  4. Tap the "Receive Shared Screen" button on Device B.
  5. On Device B, select Device A from the list and tap on the Done button.
  6. Screen Sharing is in progress!
To disable Screen Sharing, double-tap the live video preview again and stop Screen Sharing (do it on both devices). You can also control the video-quality of Screen Sharing: go to the iOS Settigns app > Heges > [adjust the slider]. Screenshot here.
[new] Alternative to Screen Sharing — scanning using a mirror.

It is possible to hold a small mirror in front of the TrueDepth camera to make scans, so that you're able to see what you're scanning. 3D Pete made this mirror holder for iPhone XS which can be used for this purpose.

When you're scanning using a mirror, the models are going to be horizontally flipped. To prevent this, please enable the Mirror-scanning toggle button. As models scanned using mirror are horizontally flipped, enabling this button will horizontally flip models that are being exported into STL/PLY. You don't need to have this option enabled when scanning with mirror — just when exporting scanned models.

How can I access scanned models and photos?
There're 3 ways you can download your models and photos;
  • via the iOS Files App — the exported .stl and .ply models will be located inside the "exported_models" folder and you can use e.g. Airdrop to send them to your Mac
  • via iTunes File Sharing — just open iTunes on your Mac and drag the "exported_models" folder
  • via built-in Wi-Fi server — instructions for successful Wi-Fi sharing:
    1. Ensure your iPhone is connected to the same Wi-Fi network as the computer you want to share with.
    2. Scan an object.
    3. Export the object to PLY and/or STL. (This needs to be done in order to have the models available.)
    4. In the Library (the list of images and scanned models) click on the sharing button that is at the top right corner a click on the "Start sharing" button (take a look here)
    5. Open a web browser on your PC and enter one of the addresses into it (for example in the image the address could be http://Tmp.local or — try more addresses, at least one should work.
    6. Now you should see a simple website on your PC where you can download the models.
How do I scan?
  • Don't move with the scanned object/scene — it absolutely needs to stay still during the whole time you're scanning.
  • Move your iPhone X slowly while scanning. If the scan quality isn't sufficient, try moving even slower — try playing with it to see how slow/fast movement influences quality (try also moving very slowly — e.g. at 5mm per second).
  • Use appropriate PRECISION settings — the 0.5, 0.8 and 1 mm Precisions are intended for very fine scanning of smaller objects and you need to scan very slowly when using them. The other Precisions (2, 3, and 4 mm) are intended to be used for scanning of larger objects.
  • If you cannot make a usefull scan with higher Precisions (i.e. less than 2 mm), try using higher precisions and experiment.
  • Ensure that the scanned object is within the scanner range (depends on the selected Precision (0.5mm, 0.8mm, …)) all the time. I recommend looking at the screen of your iPhone continuously and ensuring the scanned objects are within the scanner range all the time.
  • Revisit already scanned areas — as if you were ironing your clothes. The more you scan a certain part of an object, the less noisy it gets.
A scan doesn't look good enough.
Then you need to scan (i.e. move the phone) more slowly, especially at the very high Precisions, such as 0.5mm, 0.8mm or 1mm. Try playing with the speed of scanning to see how it influences scanning quality. For example when scanning with 0.5mm Precision try moving your iPhone very slowly (e.g. 5mm per second) and then compare it with faster movement — you should see improved quality of scan.
The scanner view looks mirrored and I don't like it — how can I fix this?
You can mirror the scanning preview in the iOS Settings app: navigate to: the iOS Settings app > Heges and enable Mirroring preview around vertical axis. Force quit the app if it's open and now the preview is mirrored! Take a look at this screenshot.
How can I perform 360° scan more comfortably?

You can use the iPhone X, XS, XS Max rotating 3D scanner by Andrew Riley.

The colors are a bit off.
Colors might be a bit off, but the scanned model (the geometry) should be intact — take a look at the model without colors (e.g. exported STL).
Which 3D viewer should I use?
I'd recommed first exporting your scanned model into PLY (contains colors) or STL (doesn't contain colors) and then using the non-AR viewer.
Use the Internal format AR viewer only when the exported PLY model is too big to be displayed.
The Heges app's 3D model viewers are meant just for a quick preview of the model — any editing of the scanned models should be done on PC or in another app.
Support: support@hege.sh