Calibration On-the-Go: WiFi or Bust!

I’m Sean Kean and I’m writing a series of How-To Guides on how to best use Occipital’s Structure Sensor with Looking Glass’s Holoflix iOS App to take volumetric video.

As much as technology lends itself to improving our livelihoods, one thing we still can’t figure out as a society is how to get around good WiFi connection when we need it. Yep, you guessed it, you need WiFi in order to calibrate the Structure Sensor — the 3D attachment for the iPad that Holoflix uses — as it stores the calibration settings in the cloud. This came as a surprise to me in the middle of a concert I was filming. Luckily I found a quick workaround.

“Something in my image looks off…”

To start, when your photographic image isn’t quite mapping to the sculptural contours of the depth canvas, sometimes this requires a re-calibration of the hardware itself. To do this, you’ll need to download a separate application for your iPad — Structure Sensor Calibrator. Here it is.

Top: Structure Sensor bracket flopping off and messing up calibration; Bottom: A properly oriented bracket

Before you go through the calibration process, check to see that your structure mounting bracket is fully pulled in at the edges and secure as in the image above. If you ever find that your mounting bracket for the Structure Sensor gets knocked over, push it downwards and open the Structure Sensor Calibrator.

Now this is the tricky part— you need to have an internet connection! It’s a fairly bizarre requirement for what seems to be a function that could be done locally. I found myself in this sorry state out at a concert making a recording.

The Sounds performing at Warsaw in Brooklyn recorded with Holoflix and demonstrating the use of swiping for rotation

So I’m at the 10th anniversary concert to celebrate The Sound’s hit album Dying to Say This To You — a favorite of mine — so you can imagine how frustrated I was when I had to stop recording the show to adjust the calibration.

Here’s what you need to know: if you don’t have any WiFi but you do have mobile phone service you can use the personal hotspot sharing on your phone to complete the calibration process. Right now Holoflix is only available on iOS only so here’s a quick guide to get yourself set up:

How to get your iPhone into personal hotspot mode
  • Check that you have signal (you don’t need more than maybe two bars)
  • Open the Settings app
  • Open Personal Hotspot
  • Tap the toggle switch in the upper right next to the label Personal Hotspot to turn on internet sharing.
  • Hoo-ray! You should now be online. Open the Calibrate app and go through the steps as prompted.

The calibration process is apparent when using the app but the main idea is as follows:

  • The Structure Sensor Calibrate app will ask you to be indoors but in a place with enough light in the photographic images so that the computer vision algorithm can pick up the details of the scene and match them up with the depth. You’ll then be asked to slide the depth image over the color image so they line up. Once you confirm this, the settings will attempt to be uploaded over the internet. If there’s no network connection the calibration wont save at all.
  • It wouldn’t hurt to re-calibrate every time you are about to shoot something important. It would also be smart to tap down the mounting bracket for the Structure Sensor every time before you hit record. Just in case.

Stay tuned for more trips and tricks on how to best use the hardware with Holoflix.

Is there anything you’re dying to know about Holoflix and volumetric film making? Write me at [email protected]

— Sean