Structure Sensor vs. iSense for 3D Scanning – with Example Scans

Over the past months I’ve received a lot of questions regarding this post about the hugely discounted iSense 3D Scanner from 3D System. I’m updating that post weekly with all the facts that I’ve gathered from readers, manufacturers and developers. I advice you to read it if you’re interested in knowing the differences and the reason why the iSense is currently offered so cheap on Amazon and eBay.

But regardless of the information in that post, I was still getting a lot of questions and remarks. So to settle this, I decided to simply an iSense myself — for $58 on eBay including bracket. Since I already own a Structure Sensor, I can now compare them hands-on instead of on claims of other people that honestly didn’t always make sense (pun sort of intended).

Before I continue, I must stress that you should really read the other post regarding possible compatibility issues if you plan on purchasing an iSense at a discount. Mine works like a charm and of the readers that have contacted me, about 75% had the same positive experience and the other 25% had a negative one. Maybe I got lucky, or maybe I just know how to work with this kind of device, I don’t know.

I’m not sure what cause the negative experience for some. Some error messages people sent me sounded more like a defective iSense than an incompatible one. And I got quite a few messages from people complaining about the scan quality of the iSense.

The big question of course is: If it works, is there any difference in scan quality?

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First, let me make one thing crystal clear:

1. Infrared depth sensors are perfectly capable of capturing the geometric shape of objects indoors and in complete darkness. They can see their own light, it’s just that your eyes can’t see infrared light.
2. If you also want to capture color information to create textures, the amount and quality of your indoor lighting makes all the difference. In the case of the sensors I’m talking about here, which use the iPad’s RGB camera, it also matters what model iPad you have. The newer and/or more expensive ones have better camera’s that are more light sensitive. Meaning less motion blur and noise in lower light conditions. Ideally, use a studio light kit indoors. I’ve made a list with some affordable light setup suggestions.
3. Since it uses infrared, it doesn’t work well outdoors. Maybe on an overcast day, but otherwise there’s usually to much actual infrared light — you know, from the sun — that will interfere with the sensor.

And before you think… “Nick has his whole state-of-the-art 3D Scan Expert laboratory set-up for this test so I can’t match that awesome scan quality”… this is my setup:

What exactly are you using?

1. An iPad mini, the cheapest compatible one you can find. Doesn’t have so much RAM, so be sure to perform a RAM Reset before scanning.
2. An Occipital Structure Sensor with firmware version 2.0 and serial number in the range 472XX
3. A 3D Systems iSense with firmware version 1.0.2 (the highest it will go, it will not receive any future firmware updates) and serial number in the range 248XX. (it appears that Occipital has whitelisted certain serial ranges to make them compatible with their apps, again read more here)
4. 3D Systems iSense App 2.2.0
5. itSeez3D 4.3
6. Occipital Structure Sensor Sample App 1.6.2
7. Skanect Pro 1.8 (the post has been updated for Skanect 1.9)
8. A mid-2012 Macbook Pro to run Skanect. Latest Nvidia CUDA driver installed. Computer-to-computer (ahdoc) WiFi network to the iPad.

iSense App

I will start with the iSense app (I published a Full Review of this app for completeness sake). You’re probably reading this because you want to buy a cheap iSense and this app by 3D Systems should always work, regardless of your serial number.

It’s important to note that after starting the app, it will show a notification about calibration:

The notification links to Occipital’s Structure Sensor Calibrator app which you can download, but not use because…

According to this post by Occipital this means my discounted iSense was indeed sold by an unofficial seller and will not be fully supported by them and not be able to use the Calibrator.

So for all tests in this post, I’m using an iSense that has not been calibrated with the dedicated app. It’s noteworthy that I bought an iSense bundled with an iPad Air 2 bracket so it is probably factory-calibrated for that device. Calibration registers the offset between the infrared sensor and the iPad’s color camera. I removed it from the bracket and put it onto the one for my iPad mini. You can see in the results below that not being able to calibrate it didn’t hurt the results. I’m confident that this is because the iPad Air 2 and iPad mini 2 have more or less the same distance between the sensor and iPad camera so it switching brackets might not work for every combination!

Let’s start with the result from the iSense app which, by the way, has to be downloaded by connecting the iPad to a computer running iTunes — a bit cumbersome, but doable:

The texture isn’t razor-sharp, but in line with what I expected. This is also true for the geometry, which you can check by putting the Sketchfab embed above in MatCap render mode.

I wanted to make the same scan in the iSense app with the Structure Sensor, but this isn’t possible.

Since the iSense has been discountinued, the in-app purchase mentioned above is no longer available. Which is kind of a shame, actually, because the iSense app is a lot more complete than Occipital’s Sample Scanner app when it comes to editing features (review soon). But if you want the best scan quality you will probably choose itSeez3D anyway.

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itSeez3D

Although I obviously don’t have an iSense that’s “unlocked” by Occipital to use with their Calibrator App, I had no problem running itSeez3D. This is by far my favorite 3D scanning app for these sensors — as you can read in my in-depth Review. True, it’s not free anymore but that’s only true if you want to download the actual 3D models for 3D printing or other purposes. It’s still free to share your scans on Sketchfab as long as you won’t allow them to be downloaded.

Here are the scans I made with itSeez3D with the — uncalibrated — iSense (top) and Structure Sensor (bottom):

You see(z) what I see(z)? They have the exact same polycount (50k) and the texture quality is also the same. Any difference between those scans are a result of me, because I’m not a robot that can perform the exact same route twice. And the texture exposure is locked on the first frame, so that explains the slight difference.

Anyway, this makes clear that A) my cheap iSense works with itSeez3D out of the box and B) it’s not necessary to calibrate the iSense for this purpose — at least in my case.

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Occipital Scanner Sample App

Although my iSense didn’t work with Occipital’s Calibrator App, it did work with their free Scanner Sample App. Again, the iSense first, then Structure Sensor:

If you look at the geometry, you’ll notice that it’s comparable to the itSeez3D examples. The polycount is also 50k for both sensors. The surface does look a bit smoother with this app.

The difference with itSeez3D is clearly in the way that app generates the texture map. The textures of the Occpital app are comparable to those of the 3D Systems app but those from itSeez3D are a lot better.

Skanect

To stream wirelessly to Skanect, which runs on a Mac or PC (you can also use the USB Hacker Cable, but you won’t have color) you need the Structure Sensor app on the same network as the computer (preferable an adhoc network) and use the Uplink feature. I had no problem running this app with my iSense.

Yes, you and I are still waiting for the new 1.9 version which promises better texture quality among other improvements. I have beta-tested that version and it indeed does improve texture quality.

Because I still don’t know when then new version will finally be released (and because my beta expired) I decided to use version 1.8 for this comparison, since you can actually download that.

Version 1.9 indeed delivers better texture quality. Read my full review of Skanect 1.9 here. Below is an example of the just the bust scanned with the new High Resolution Color Setting:

In my tests Skanect also worked fine with my iSense and I couldn’t discover any quality differences from using the Structure Sensor.

The original examples from Skanect 1.8 have been removed from this post but can still be viewed in this Sketchfab Collection.

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Verdict

So, now I’ve tested it for you: I bought a new, but very cheap iSense on eBay (where most sellers offer international shipping. US residents can also check out the Discounted iSense deals on Amazon).

Yes, I indeed got an iSense that will not be officially supported — or “unlocked” as they call it — by Occpital, so it will never work with their Calibrator app. But I had no troubles with using it anyway. I put the iSense on a bracket for a different iPad and used the iSense app (which is no longer available as of May 2017), the Structure Sensor Sample app, the Structure Sensor app with Skanect and itSeez3D to make scans of objects without problems.

And without any noticable difference in quality compared to my actual Structure Sensor.

So there you have it. Please note that this is my situation and no guarantee for purchases you will make, which are strictly at your own risk. I would greatly appreciate it if you leave your experiences in the comments below — especially if they are different from mine.

Happy Scanning!

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iSense +
iPad Air Bracket*

*also fits on 5th gen iPad (2017)
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iSense +
iPad Air 2 bracket**

**also fits on iPad Pro 9.7″
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iSense +
iPad mini 2 bracket

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