Depth Camera Target Tracking via Skeletal Model Rasterization

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Solution Overview

Problem

Existing computer vision applications face challenges in accurately tracking targets, especially when targets move into complex poses or occlude each other, requiring efficient and robust systems to interpret user movements as game controls or application inputs.

Innovation Solution

A method utilizing depth cameras to acquire depth information, model targets with skeletal representations, and adjust poses based on differences between observed and synthesized depth images, allowing for real-time tracking and control of game characters or application elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If traditional control systems are used to manipulate game characters, then control precision can be maintained, but ease of operation deteriorates due to complicated controls that are difficult to learn and different from actual game actions

Engineering Contradiction:
Improveease of controlVSAvoidcontrol system complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The system creates a virtual model (avatar) that copies the user's physical movements in real-time. The depth camera captures the user's skeletal pose, and the virtual avatar replicates these movements, allowing natural motion transfer without complex control mappings. This eliminates the need for learned control schemes while maintaining precise character manipulation.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The patent replaces traditional mechanical control interfaces (controllers, keyboards) with a vision-based system using depth cameras and computer vision algorithms. This substitution enables natural motion capture and automatic translation to game controls, eliminating the learning curve associated with conventional control mechanisms.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If depth-based visual tracking is implemented to enable natural movement control, then ease of operation improves, but measurement precision deteriorates when targets move into complex poses or occlude each other

Engineering Contradiction:
Improvenatural movement controlVSAvoidtracking accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The system segments the user's body into individual skeletal components (joints, limbs, torso) and tracks each segment independently. This segmentation allows the system to maintain accurate tracking even when parts of the body are occluded, as it can infer the positions of hidden segments based on the positions of visible segments and anatomical constraints.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a virtual skeletal model as an intermediary between the depth camera data and the final tracking results. This model serves as a mediator that fills in missing information from occluded or ambiguous depth data by using anatomical priors and motion constraints, thereby maintaining tracking accuracy in challenging scenarios.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Speed

If real-time tracking is achieved through continuous depth image processing, then speed of response improves, but use of energy increases due to continuous computation and model adjustment

Engineering Contradiction:
Improvetracking speedVSAvoidcomputational energy consumption
Core Design Contradiction:
SpeedVSUse of energy by moving object

Solution Approach 1:

The system performs tracking and model adjustment at discrete time intervals (frames) rather than continuously. By processing depth images periodically at the frame rate of the camera and only updating the virtual model when necessary, the system maintains real-time responsiveness while significantly reducing computational energy consumption compared to continuous processing.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent pre-establishes the virtual skeletal model and its parameters before tracking begins. This preliminary setup allows the system to use the pre-configured model for rapid real-time matching against depth images without needing to create or extensively process complex models during operation, thereby reducing ongoing computational energy requirements.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2391988B1Visual target tracking
Publication Date: 2022.06.08 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP2391988B1 patent drawingFigure 1A
  • EP2391988B1 patent drawingFigure 1B
  • EP2391988B1 patent drawingFigure 2~3

AI summary

A method of tracking a target includes receiving an observed depth image of the target from a source and obtaining a posed model of the target. The model is rasterized into a synthesized depth image, and the pose of the model is adjusted based, at least in part, on differences between the observed depth image and the synthesized depth image.