I'm trying to implement a simple augmented reality tool for Android. All it
needs to do is take as input my location and device orientation and the
location of another device and present a camera view with an icon overlaid
in the appropriate place in an appropriate size.
I'm stuck in two places:
I wrote code to get updates for the current azimuth, pitch, and roll of the
device. The code looks like this:
private final SensorEventListener goodListener = new SensorEventListener() {
private float[] magneticValues;
private float[] accelerometerValues;
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_MAGNETIC_FIELD:
magneticValues = event.values.clone();
break;
case Sensor.TYPE_ACCELEROMETER:
accelerometerValues = event.values.clone();
break;
}
if (magneticValues != null && accelerometerValues != null) {
float[] outR = new float[9];
float[] orientationValues = new float[3];
SensorManager.getRotationMatrix(outR, null,
accelerometerValues, magneticValues);
SensorManager.getOrientation(outR, orientationValues);
double azimuth = Math.toDegrees(orientationValues[0]);
double pitch = Math.toDegrees(orientationValues[1]);
double roll = Math.toDegrees(orientationValues[2]);
}
}
When I use logging to read these values, they seem relatively stable, but
they do not seem to correspond to angles around any natural set of axes,
and I can't figure out what the numbers represent. How should I interpret
these numbers?
The tutorial at http://www.devx.com/wireless/Article/42482/0/page/3 takes a
much simpler approach, but I cannot get it to work.
Once I have my device's azimuth, pitch, and roll, along with my latitude
and longitude and that of the other device, how can I determine where to
put the icon on the screen? This seems to be a complicated geometry problem
where we must imagine the view field of the camera as an infinite cone,
project it onto the surface of the earth, and see if the other location is
inside the projected area, but this seems awfully complicated. Is there a
better way that I'm overlooking?
Thanks!
- Jeff
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