System and method for object tracking

Abstract

A hand-manipulated prop is picked-up via a single video camera, and the camera image is analyzed to isolate the part of the image pertaining to the object for mapping the position and orientation of the object into a three-dimensional space, wherein the three-dimensional description of the object is stored in memory and used for controlling action in a game program, such as rendering of a corresponding virtual object in a scene of a video display. Algorithms for deriving the three-dimensional descriptions for various props employ geometry processing, including area statistics, edge detection and / or color transition localization, to find the position and orientation of the prop from two-dimensional pixel data. Criteria are proposed for the selection of colors of stripes on the props which maximize separation in the two-dimensional chrominance color space, so that instead of detecting absolute colors, significant color transitions are detected. Thus, the need for calibration of the system dependent on lighting conditions which tend to affect apparent colors can be avoided.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to computer vision systems, and more particularly to a system in which an object is picked-up via an individual video camera, the camera image is analyzed to isolate the part of the image pertaining to the object, and the position and orientation of the object is mapped into a three-dimensional space. A three-dimensional description of the object is stored in memory and used for controlling action in a game program, such as rendering of a corresponding virtual object in a scene of a video display. [0003] 2. Background of the Invention [0004] Tracking of moving objects using digital video cameras and processing the video images for producing various displays has been known in the art. One such application, for producing an animated video version of a sporting event, has been disclosed by Segen, U.S. Pat. No. 6,072,504, the disclosure-of which is incorporated in the present specification ...

AI Technical Summary

Benefits of technology

[0011] It is a principal object of the present invention to provide an object tracking system suitable for video game programs which overcomes the aforementioned disadvantages of the conventional art, enabling tracking of the position and orientation of an object or prop which serves as an input device for effecting action in the game program.

[0012] Another object of the invention is to provide alternative interfaces for games, wherein rather than using a conventional joystick, the user can stand in front of a video camera connected to the game console device, and by physically moving or manipulating an object within view of a single camera, cause a corresponding action to occur in the game.

[0015] A still further object of the invention is to provide techniques for the selection of object colors which maximizes one's ability to discriminate, on the basis of color transitions, the pixel groups from a video image which belong unambiguously to the manipulated object and which provide the needed information for deriving a description of three-dimensional position and orientation of the object.

Problems solved by technology

Thus, the system of Segen is not capable of reconstructing position and orientation of an object, whether moving or at rest, from a two-dimensional video image using a single video camera.

However, in spite of the above knowledge and techniques, problems continue to hinder successful object tracking, and a particularly difficult problem is extracting precisely only those pixels of a video image which correspond unambiguously to an object of interest.

For example, although movement of an object having one color against a solid background of another color, where the object and background colors vary distinctly from one another, can be accomplished with relative ease, tracking of objects, even if brightly colored, is not so easy in the case of multi-colored or non-static backgrounds.

Changes in lighting also dramatically affect the apparent color of the object as seen by the video camera, and thus object tracking methods which rely on detecting a particular colored object are highly susceptible to error or require constant re-calibration as lighting conditions change.

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