XR Hand Chirality Estimation Using Joint Bending Angles

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Solution Overview

Problem

Existing XR devices face challenges in accurately and efficiently estimating hand chirality due to the variability in hand shapes, sizes, and movements, leading to potential errors in tracking and interpreting user gestures, and introducing computational inefficiencies and latency.

Innovation Solution

XR devices process tracking data to determine multiple bending angles associated with a hand, using a geometrically defined reference vector to estimate chirality without relying on machine learning models, and combine this with a rules-based approach for enhanced accuracy and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If machine learning models are used to estimate hand chirality, then accuracy may be improved, but computational complexity and latency increase

Engineering Contradiction:
Improvehand chirality estimation accuracyVSAvoidcomputational complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces machine learning models (complex computational system) with a rules-based geometric analysis system that calculates bending angles and determines chirality through predefined geometric relationships. This substitution reduces computational complexity while maintaining estimation accuracy by leveraging the inherent geometric properties of hand structures.

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

Solution Approach 2:

The patent extracts only the essential geometric features (bending angles of finger joints) needed for chirality estimation, discarding the need for complex machine learning models. By focusing solely on the critical geometric parameters, the system achieves accurate chirality determination with significantly reduced computational requirements.

Inventive Principle:
Principle #2Taking out (Extraction)

2Measurement precision

If machine learning models are used to estimate hand chirality, then accuracy may be improved, but processing time and latency increase

Engineering Contradiction:
Improvehand chirality estimation accuracyVSAvoidprocessing latency
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces computationally intensive machine learning inference with lightweight geometric calculations that compute bending angles and apply simple decision rules. This substitution dramatically reduces processing time and latency while maintaining the accuracy needed for real-time XR applications.

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

Solution Approach 2:

The patent uses simple, computationally inexpensive geometric calculations instead of heavy machine learning models. These lightweight calculations can be performed rapidly and discarded, enabling real-time chirality estimation without the computational burden of sustained machine learning processing.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Device complexity

If traditional tracking methods are used, then device complexity is reduced, but reliability of hand chirality estimation deteriorates due to hand variability

Engineering Contradiction:
Improvetracking system complexityVSAvoidchirality estimation reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent applies localized geometric analysis to specific finger joints, calculating bending angles for each joint individually. This local quality approach allows the system to adapt to variations in individual finger configurations while maintaining overall reliability, as each joint's geometry is analyzed independently according to its specific characteristics.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the approach from using fixed, generic hand models to dynamically calculating bending angles based on actual tracked joint positions. By adapting the geometric parameters to the specific hand configuration being observed, the system maintains high reliability across diverse hand shapes and sizes without increasing overall system complexity.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS20250383702A1Hand chirality estimation for extended reality tracking
Publication Date: 2025.12.18 SNAP INC
  • US20250383702A1 patent drawing
  • US20250383702A1 patent drawing
  • US20250383702A1 patent drawing

AI summary

Examples in the present disclosure relate to hand chirality estimation. Tracking data captured by one or more sensors associated with an extended reality (XR) device is processed to determine positions of a plurality of joints of a hand of a person. A reference vector is generated based on a first subset of the positions. The first subset of the positions includes positions of at least two metacarpophalangeal joints. A plurality of bending angles is determined based on at least a second subset of the positions. Each bending angle represents an angle between a respective pair of articulating bones that is measured in relation to the reference vector. An estimated chirality of the hand is identified based on the plurality of bending angles. Operation of the XR device is controlled using the estimated chirality of the hand.