Calibration of portable devices in a shared virtual space

1. A method comprising:

associating a first device to a reference point in a three-dimensional (3D) space;

calculating by the first device a position of the first device in the 3D space based on inertial information captured by the first device, wherein calculating the position uses dead reckoning by estimating a current position of the first device based upon a previously determined position and advancing the previously determined position based upon a speed of the first device over elapsed time and course;

capturing images with a camera of the first device;

identifying locations of one or more static features in the images;

correcting the position of the first device based on the identified locations of the one or more static features, the correcting further includes attributing a difference between a first estimate calculated based on inertial information and a second estimate, calculated based on the identified locations of the one or more static features, to a dead reckoning error; and

presenting a view of an interactive scene in a display of the first device, wherein operations of the method are executed by a processor.

2. The method as recited in claim 1 , wherein calculating the position is performed at predetermined intervals or after a predetermined number of inertial measurements.

3. The method as recited in claim 1 , wherein correcting the position further includes:

adjusting the first estimate to have an expected location of a first static feature be equal to a measured location of the first static feature.

4. The method as recited in claim 1 , wherein the interactive scene is tied to the reference point and includes virtual objects.

5. The method as recited in claim 1 , wherein the view shows all or part of the interactive scene as observed from a current location of the first device.

6. The method as recited in claim 1 , wherein the one or more static features include one or more of an edge of table, or a window, or a television, or a light source, or a painting on a wall.

7. A method comprising:

associating a first device to a reference point in a three-dimensional (3D) space;

exchanging position information between the first device and a second device to enable the second device to associate to the reference point;

calculating by the first device a position of the first device in the 3D space based on inertial information captured by the first device, the calculating by the first device the position of the first device further includes utilizing dead reckoning by estimating a current position of the first device based upon a previously determined position and advancing the previously determined position to the current position;

capturing images with a camera of the first device;

identifying locations of one or more static features in the images;

correcting the position of the first device based on the identified locations of the one or more static features and inertial information, the correcting is applied to a dead reckoning error; and

presenting a view of a shared interactive scene in a display of the first device, wherein operations of the method are executed by a processor.

8. The method as recited in claim 7 , wherein the first device and a second device exchange dead reckoning data and static feature information.

9. The method as recited in claim 7 , further including:

obtaining by the first device a relative position of the second device utilizing WiFi triangulation, player face detection, or identification of the second device within the captured images.

10. The method as recited in claim 7 , further including:

obtaining by the first device a relative position of the second device utilizing audio triangulation by utilizing ultrasonic communication and one or more directional microphones.

11. The method as recited in claim 7 , wherein the view in the first device is independent from the view in the second device, the view in the first device being based on a relative position of the first device with respect to the shared interactive scene.

12. The method as recited in claim 7 , further including:

determining a relative position of the second device with reference to the first device based on image analysis to identify a geometry of the second device in the images.

13. The method as recited in claim 7 , wherein the view shows all or part of the shared interactive scene as observed from a current location of the first device.

14. The method as recited in claim 7 , wherein operations of the method are performed by a computer program when executed by one or more processors, the computer program being embedded in a non-transitory computer-readable storage medium.

15. A non-transitory computer-readable storage medium storing a computer program, the computer-readable storage medium comprising:

program instructions for associating a first device to a reference point in a three-dimensional (3D) space;

program instructions for calculating by the first device a position of the first device in the 3D space based on inertial information captured by the first device, wherein the calculating by the first device the position of the first device further includes utilizing dead reckoning by estimating a current position of the first device based upon a previously determined position and advancing the previously determined position based upon a speed of the first device over elapsed time and course;

program instructions for capturing images with a camera of the first device;

program instructions for identifying locations of one or more static features in the images;

program instructions for correcting the position of the first device based on the identified locations of the one or more static features, the correcting further includes attributing a difference between a first estimate calculated based on inertial information and a second estimate, calculated based on the identified locations of the one or more static features, to a dead reckoning error; and

program instructions for presenting a views of an interactive scene in a display of the first device, wherein the interactive scene is tied to the reference point and includes virtual object.