Google Cardboard for Nexus 7 Notes

Previous version was an enlarged version of the official cardboard version 1 design with larger lenses. This post is a collection of my notes taken during the process. Not a tutorial.

I started by cutting out a miniature version of the official cardboard version 2 in order to understand how it goes together. It was overly complex for my needs so I developed a simplified design with the tablet sticking out the top so the screen can be used directly as an input button.

Lens info:

Ajax Scientific Polished Glass Double-Convex (Bi-Convex) Lens, Spherical, 38 mm Diameter, 50 mm Focal Length

Lens was actually 41 mm diameter, not 38 mm


link to turbocad file –
link to dxf file –
link to dwg file –

The viewer was assembled from 3 mm thick cardboard. The shapes were printed and taped to the cardboard to use as a template for creating the pieces. The pieces were assembled using a hot glue gun. The face and bottom pieces were covered with transparent tape to avoid oil and sweat stains on the cardboard.
Nexus 3D model from TurboSquid –
Artist: art_setter factory
Profile QR-Code Generator
from desktop pc open the web page
then open the indicated web address in the tablet
if doesn’t work refresh the desktop web page and use the new indicated web address, repeat until it works
make adjustments on the pc until the tablet looks good then generate the qr code

Information and qr code updated October 5, 2021. Comparing the sizeof a objects in a scene with their size in another viewer (androiod phone and oculus rift s) showed that objects looked smaller than they should. The cardboard instructions for generating the code say to use the distance from the lens to the screen with a double arrow from the back of the lens to the screen. If the measurement is taken from the center line of the lens to the screen the apparent scale of objects is correct.

My Information:
Nexus7Home v2 Nexus7_2021_stl50
Primary Button = Touch
Screen to lens = 45.5 mm 50 mm
Inter-lens distance = 64.0 mm
Screen vertical alignment = Bottom
Distortion K1 = 0.310
Distortion K2 = 0.570

Note that the QR Code needs good lighting to work. Other android scanners will read it in low light, but the cardboard app needs it to be bright.

Feb 12, 2019 – google qr codes stopped working, “Unrecognized QR code”. Workaround is to use a barcode reader app and open the link in a browser, magically cardboard is setup with the proper qr code. Barcode Scanner+ worked for me. There was no indication that anything happened until after opening a vr app and seeing that the viewer changed.

Resolved (sort of) – "Unrecognized QR Code" every time I scan any QR code from GoogleCardboard

get shapes from TurboCAD into trueSpace:
remove all text and dimensions
convert circles and arcs to polylines (explode)
make closed shapes via join polylines
export scale depends on viewport scale

Sketchy Unity 3D Notes:
Got it working but a lot of fiddling around and not sure of anything
Daydream technical preview – can be used along side a regular unity install
gvr unity sdk – for samples
to find SDK and JDK path for modern Android Studio
open Android Studio
File > Settings
Appearance & Behavior > System Settings > Android SDK – will show the location for the SDK
The JDK is at C:\Program Files\Android\Android Studio\jre
These path values go into Unity – Edit > Preferences > External Tools
Also enable VR support and set API level 19 also download api 19 inside android studio
Latest Daydream Unity has lag/frame rate problems?

TurboCAD Side Notes: TurboCAD v14 does not work properly with Windows 10. Use of AEC Dimension Styles will cause instant crash. Text tools cause instant crash. The workaround is to save files to v12 format files and ignore the warning messages when using copy and paste. If file is v14 immediately save as v12, close file and reload it. Features unique to v14 will not fully save to v12, but it wasn’t an issue for this project. Printing from model view does not center properly, so page setup values must be set manually.
From old print notes:
in model space
View > Create View, then define the region and give it a name

Workspace > PaperSpace > Insert, or use an existing Paper tab
switch to the paper space
Insert > Viewport then goto the previously defined paper
select the viewport rectangle and right click for it’s properties
Viewport > Scale check “Fixed”
type in the value which does not show in the dropdown list -> “1 in = 25.4 mm”

now will print to size when using the defined paper

New information(Feb 2018) about turbocad problems in windows 10.

To save a tcw file do not use File > Save or File > Save As…

Use File > Extract To… ,  select the Content check box then open Drawing Setup and uncheck Styles