This document provides an overview of coding a virtual reality application for Android using the Google Cardboard SDK. It discusses setting up the coding environment in Android Studio, the key components of a Cardboard VR app including the manifest file, Cardboard activity, custom renderer, and 3D content models. The custom renderer implements the StereoRenderer interface and handles stereoscopic rendering and distortion correction. The document also provides code snippets for setting permissions in the manifest and implementing the onDrawEye method in the custom renderer.

1. Coding a VR
Application
in Android
A Practical Guide

2. Virtual Reality @
CommonFloor

3. Virtual Reality @
CommonFloor

4. Contents
❖ Introduction to Google Cardboard SDK for Android
❖ Requirement of separate SDK for VR ?
❖ Getting Started with First Android Application for VR
❖ Setup of coding environment
❖ Overview of code

5. Intro to Google Cardboard
SDK
❖ Cardboard SDK for Android enables developers familiar with OpenGL to
quickly start creating VR applications.
❖ The toolkit simplifies many common VR development tasks, including:
❖ Lens distortion correction.
❖ Head tracking.
❖ 3D calibration.
❖ Side-by-side rendering.
❖ Stereo geometry configuration.
❖ User input event handling.

6. Setup of Coding Environment
❖ Building the demo app requires:
❖ Android Studio 1.0 or higher
❖ https://developer.android.com/sdk/index.html
❖ Version 19 of the Android SDK
❖ A physical Android device running Android 16 (Jelly
Bean) or higher

7. Lets start coding
❖ Main components of Android VR Application
❖ Manifest file
❖ Cardboard Activity
❖ Custom Renderer
❖ Content Model

8. Android Manifest File
Need to specify following permissions in manifest file
❖ NFC — Input Mechanism used by cardboard trigger button
<uses-permission android:name="android.permission.NFC" />
❖ Vibration Sensor — Haptic Feedback mechanism for certain events in Application
<uses-permission android:name="android.permission.VIBRATE" />
❖ Read and write to external storage
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
❖ Specify minimum and target SDK version
<uses-sdk android:minSdkVersion="16" android:targetSdkVersion="19"/>
❖ Specify the OpenGL ES version that device must support to run the application
<uses-feature android:glEsVersion="0x00020000" android:required="true" />

9. Cardboard Activity
❖ Starting point for coding a cardboard app.
❖ Base activity that provides easy integration with
Cardboard devices.
❖ Exposes events to interact with Cardboards.
❖ Uses sticky immersive mode, in which the system UI is
hidden, and the content takes up the whole screen.

10. Custom Renderer
❖ Custom Renderer for CardboardView
❖ Implements the CardboardView.StereoRenderer interface
❖ Delegates all stereoscopic rendering details to the view
❖ All stereoscopic rendering and distortion correction details are abstracted from the renderer and managed
internally by the view
❖ Overrides the following important methods
// Prepares OpenGL ES before we draw a frame.
// @param headTransform The head transformation in the new frame.
@Override
public void onNewFrame(HeadTransform headTransform) {
// Called when a new frame is about to be drawn.
// Any per-frame operations not specific to a single view should happen here.
}
@Override
public void onDrawEye(Eye eye) {
// Draw the frames for each eye
}

11. Custom Renderer
OnDrawEye Function
// Draws a frame for an eye.
// @param eye The eye to render. Includes all required transformations.
@Override
public void onDrawEye(Eye eye) {
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
. . .
// Apply the eye transformation to the camera.
Matrix.multiplyMM(mView, 0, eye.getEyeView(), 0, mCamera, 0);
// Set the position of the light
Matrix.multiplyMV(mLightPosInEyeSpace, 0, mView, 0, LIGHT_POS_IN_WORLD_SPACE, 0);
// Build the ModelView and ModelViewProjection matrices
// for calculating cube position and light.
float[] perspective = eye.getPerspective(Z_NEAR, Z_FAR);
Matrix.multiplyMM(mModelView, 0, mView, 0, mModelCube, 0);
Matrix.multiplyMM(mModelViewProjection, 0, perspective, 0, mModelView, 0);
drawCube();
// Draw rest of the scene.
. . .
}

12. Content for VR - 3D Models
❖ Consists of any 3D model that we want to render in our application
❖ Can be a simple model like a sphere or cube
❖ Can be complex models of house, players etc to create a real 3D
scene.

13. Wrap it up and Lets Code !!!
3D
Assets
Carboard.jar
Google Cardboard
Android Application
Redistributable
APK
Cardboard SDK
Compatible
Android Phone
+ =
=
Android
Code +