Calibration of portable devices in a shared virtual space

1. A method for generating an interactive space viewable through at least a first and a second device, the method comprising:

detecting from the first device a location of the second device or detecting from the second device a location of the first device, wherein the first device and the second device are handheld devices;

exchanging synchronization information data between the first and second devices to identify a reference point in a three-dimensional (3D) space relative to a physical location of the first and second devices in the 3D space, wherein the first and second devices establish the physical location in the 3D space of the other device when setting the reference point; and

generating views of an interactive scene in corresponding displays of the first and second devices, wherein the corresponding device acts as a camera viewing into the interactive scene, the interactive scene is tied to the reference point and includes virtual objects, each view showing all or part of the interactive scene and showing the interactive scene as observed from a current location of the corresponding device with a viewing angle of the corresponding camera, wherein device movement in the 3D space causes the corresponding view to change according to the current location and the viewing angle.

2. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

detecting that the first device has tapped a first object at a first time;

receiving information that the second device has tapped a second object at a second time; and

determining that the first device has tapped the second device when the first and the second times are substantially simultaneous.

3. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

recognizing the second device in an image taken with a camera in the first device.

4. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

detecting a light source in the second device in an image taken with a camera in the first device.

5. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

detecting a distance between the first device and the second using a depth camera.

6. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

recognizing a display of the second device in an image taken with a camera in the first device.

7. The method as recited in claim 1 , wherein detecting from the first device the location of the second device further includes:

recognizing a pattern in the display of the second device in an image taken with a camera in the first device.

8. The method as recited in claim 1 , further including:

tracking motion of the first device by the first device, wherein tracking motion of the first device further includes using dead reckoning to determine the current location of the first device.

9. The method as recited in claim 8 , wherein tracking motion of the first device further includes:

tracking location of static features in the 3D space using image information; and

correcting shift in dead reckoning based on the location of the static features.

10. The method as recited in claim 9 , wherein the static features are selected from a group consisting of an edge of a table, a corner in a room, a window, or a television set.

11. The method as recited in claim 1 , further including:

resetting location tracking modules in the first device and the second device when the reference point is identified.

12. The method as recited in claim 1 , wherein the viewing angle is defined as a vector with origin in a center of the display and with a direction perpendicular to and away from the display.

13. A method for generating an interactive space viewable through at least a first and a second device, the method comprising:

detecting a tapping between the first device and the second device, wherein the first device and the second device are handheld devices;

exchanging synchronization information data between the first and second devices to identify a reference point in a three-dimensional (3D) space relative to a physical location of the first and second devices in the 3D space when the tapping was detected; and

generating views of an interactive scene in corresponding displays of the first and second devices, wherein the corresponding device acts as camera viewing into the interactive scene, the interactive scene is tied to the reference point and includes virtual objects, each view showing all or part of the interactive scene and showing the interactive scene as observed from a current location of the corresponding device with a viewing angle of the corresponding camera, wherein device movement in the 3D space causes the corresponding view to change according to the current location and the viewing angle.

14. The method as recited in claim 13 , wherein detecting the tapping further includes:

detecting that the first device has tapped a first object at a first time;

receiving information that the second device has tapped a second object at a second time; and

determining that the first device has tapped the second device when the first and the second times are substantially simultaneous.

15. The method as recited in claim 14 , wherein detecting that a first device has tapped a first object further includes:

identifying an abrupt change in motion of the first device.

16. The method as recited in claim 15 , wherein identifying the abrupt change is based on information from a 3-axis accelerometer.

17. The method as recited in claim 13 , wherein each device is configured for interaction with the virtual objects.

18. A portable handheld device for sharing a virtual reality among portable handheld devices, the portable handheld device comprising:

a position module for tracking a position of the portable handheld device, the position module configured to detect a location of a second device in reference to a location of the portable handheld device;

a communications module for exchanging synchronization information data between the portable handheld device and the second device, wherein a reference point in a three-dimensional (3D) space relative to a physical location of the portable handheld device in the 3D space is identified based on the synchronization information;

a view generator that creates a view of an interactive scene that is tied to the reference point and includes virtual objects, wherein the portable handheld device acts as camera viewing into the interactive scene, the view showing all or part of the interactive scene as observed from a current location of the portable handheld device with a viewing angle of the camera, wherein portable handheld device movement in the 3D space causes the view to change according to the current location and the viewing angle; and

a display for showing the view.

19. The portable handheld device of claim 18 , wherein the position module includes location tracking modules, wherein the location tracking modules further include:

a 3-axis accelerometer;

a 3 axis gyroscope;

a camera;

a GPS module; and

a depth camera.

20. The portable handheld device of claim 18 , wherein detecting the location of the second device further includes:

detecting that the portable handheld device has tapped a first object at a first time;

receiving information that the second device has tapped a second object at a second time; and

determining that the portable handheld device has tapped the second device when the first and the second times are substantially simultaneous.