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, only iPhone X) 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.

How can I access scanned models and photos?
Either via the built-in Wi-Fi server, or via the iOS Files App. 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.
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