Pan and Tilt

A webcam does not typically express pan and tilt values in pixels, the smallest unit of image capture by the webcam sensor. For example, the Logitech C920 and the Microsoft LifeCam VX-5000 have a range of +/-36,000 units, far greater than the pixel count in each axis.

The webcam accepts pan and tilt as a pair of (x, y) values. Thus the SDK pan and tilt methods handle these values only as a pair, in a special class named PanTiltHolder. This class has two fields, named pan and tilt, of type integer.

Here’s an example to illustrate using the basic methods:

myHolder.pan = 5;                  // assign the pan field
myHolder.tilt = 10;                // assign the tilt field
myPtzControl.setPanTilt(myHolder);         // command the webcam with (x, y) pair

To retrieve values from the webcam:

newHolder = myPtzControl.getPanTilt();      // retrieve (x, y) pair from webcam
int currentPanValue = newHolder.pan;        // access the pan value
int currentTiltValue = newHolder.tilt;      // access the tilt value

The above examples assume these objects already exist:

PtzControl myPtzControl = vuforia.getCamera().getControl(PtzControl.class); // create PTZ webcam control object
PtzControl.PanTiltHolder myHolder = new PtzControl.PanTiltHolder();         // instantiate input holder object
PtzControl.PanTiltHolder newHolder;                                 // declare output holder object

The webcam may support minimum and maximum allowed pan/tilt paired values. Subject to the control object guidelines shown above, these can be retrieved as follows:

minPanTiltHolder = getMinPanTilt();
maxPanTiltHolder = getMaxPanTilt();

There are no set() methods for min and max pan/tilt values; these are hard-coded in the webcam’s firmware. Note that firmware settings may vary among different versions of the same webcam model.

These pan and tilt methods are called on a PtzControl object, as described above for exposure.