Sunday, January 7, 2018

Augmented Reality Vuforia Demo for Android & Unity


Demonstration of Augmented Reality using Vuforia libraries, on 2 separate builds for Android (Android Studio , Unity 2017.2)

3D AR object tracking using ImageTarget & Virtual Buttons

Unity native AR integration requires Android v7 / iOS ARKit,
however adding Vuforia AR libraries allows backlevel Android support (back to v4.1 as of Unity 2017.2)

Please see the transcript for links & background info.

Transcript + timecodes

Hi, This is Morte from PCAndVR,
with a video demonstrating Augmented Reality using Vuforia libraries, on builds for Android (using Android Studio & Unity 2017.2)

If you're not familiar with Augmented Reality (AR), it means using a device to synchronise virtual objects into the sensory field (e.g. visual/auditory) through which we experience the real world.
A key feature of AR is locking a virtual reference frame into a live camera image of either a specific image target, a 3D object, or a surface (ground plane).  This reference frame becomes a stable centre point for generated 3D objects to exist such that they appear synchronised with the real world in the device's camera image.
Because an AR object or image target can be tracked in 3D space, it actually provides a form of head tracking for Mixed Reality (XR) if you use a mobile Virtual Reality (VR) head mount with a camera opening such as Samsung's Gear VR or custom Google Cardboard headsets.

Without head tracking, VR headsets can only provide 6DoF (degrees of freedom) rotation from a single point, and no translational movement in virtual space, adding to motion sickness.
AR devices can be something as simple as a recent model mobile phone or tablet with camera.
Head mounted AR devices can be more useful for hands-free operation and keeping virtual objects in the field of view, but typically there are weight and portability issues with tethered head mount devices, and image quality limitations on current untethered glass-frame devices.

This video will demo 3D AR object tracking using ImageTarget & Virtual Buttons, as they are reliable and simple to implement.
First up, we have the Android Studio built app, which largely contains the same feature set as the Unity app, albeit using simpler models and older image targets.
The 1st Android Studio example uses the stones image target.  The added 3D object is a teapot, originating from the famous 1975 Utah teapot 3D model.

Using the app we can show the teapot from various distances, angles, and even zoom in on the inside of the spout, with the teapot visually appearing fairly stable against the stones image target.

The image targets are printed on A4 paper from files in the supplied library, and are designed to be high contrast, with numerous well defined edges and non-repeating features.  This allows detection and tracking even if only a portion of the image is visible in the camera field.

The 2nd Android Studio example uses the wood background image target, with four virtual buttons.   Each button gets mapped with a virtual rectangle surrounding it to detect occlusion by real world objects, effectively meaning the button has been pressed.  In this case, it changes the colour of the teapot to match the colour of the virtual button covered by my fingers: red, blue, yellow, and green.

Next, we move to the Unity build of the same type of example features, with image targets and non-interactive 3D objects, and virtual buttons to allow interactive 3D object behaviour using the same image targets.

Here we have a standing astronaut, which can jitter if the AR device is not held steady, an effect worsened by the model's height, and relatively small target image size
next is an oxygen cylinder which is significantly more stable due to the 3D model being smaller and positioned closer to the target surface,
and an animated drone, which while small, can jitter in the hovering position above the target surface.

I coded a custom 3D image of my own showing an empty gamelevel platform, using the stones image target and downloaded .xml file, but I could have used any suitable custom image with the Vuforia web xml generator.

Finally, the Unity build's virtual buttons feature shows the astronaut waving after a button press,
the oxygen cylinder displaying an infographic dropdown visual,
the drone emitting a blue projection field.
and the fissure changing from white steam to dark red.

In concluding, we saw some limitations of smaller, less complex image targets in terms of feature detection & target tracking,
with resultant visual instability of mapped 3D objects, worsening further above the surface of the target,
and objects disappearing at low incident angles to the target, where feature detection is not possible.  
Both these limitations can be mitigated somewhat through use of 3D object targets or larger complex multiple image targets on 3D objects,
since the detection should still clearly see features of one target even if those of another become occluded or at a low angle.

For further background info & links, please see the transcript for this video.

And that's it, so thanks for watching!

Background info

If you are thinking of doing your own Vuforia AR builds for Android,
The 1st demo uses an app built on Android Studio using the Vuforia Android SDK:

A number of books & online tutorials exist, but can be confusing due to the deprecated legacy Android Vuforia library API which used QualComm. & QCAR. naming.
Now Vuforia library naming is standalone, and Android native builds require Android Studio, replacing Eclipse.
However it still required significant manual tweaking and customisation for me to convert deprecated code from legacy Eclipse format into Gradle-based Android Studio framework.
It is really not worth pursuing Vuforia libraries for Android Studio since the Vuforia Unity SDK makes the entire process simple and modularised, utilising drag n drop gameobjects.

It is already far easier to go straight to Unity for both Augmented, Virtual, & mixed reality  (XR) features.
Unity native AR integration requires Android v7 / iOS ARKit,
however adding Vuforia AR library support allows backlevel Android support (back to v4.1 as of Unity 2017.2)
Don't bother with the downloadable legacy Vuforia library .unitypackage for Unity 5.x.x or earlier, there are too many deprecations to contend with.

Aside from using the image targets from the supplied library, creating your own image targets for use in an app consists of uploading an image to your Vuforia web account, and processing them for the appropriate platform. 
Internally, Vuforia converts images into feature points, downloaded from the site as an xml file used in the app as a form of 2D vector UV mapping. 
These feature points are used for tracking in conjunction with the Vuforia image detection & processing algorithms, and any chosen 3D objects can be overlaid onscreen, locked to the detected target so that movement of the device's camera shows the chosen 3D objects from the appropriate angle and distance, matching the real world target.

This is a general introduction to Vuforia:

This link helps you get started with Vuforia in Unity:

Some tips & tricks for Vuforia on Unity:

Vuforia's legal doco allows for free use of a subset of features during app development:

Vuforia requires setting up a Licence for each Unity project/application you develop

If you use the supplied example code from the .unitypackage in Asset Store (for Unity 2017.2 or later), be sure to use the link here in the notes to understand how to successfully apply custom image targets without them being overriden by the sample code:

Google Daydream View VR requires specific compatible Android v7 phones such as Google's Pixel 2 or Samsung Note 8/Galaxy S8, but reference headsets do not allow rear camera visibility, so no AR or XR on those.

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.