Simulated Hair Strand Transfer With Shape-Preserving Constraints

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Solution Overview

Problem

Existing computer-based digital animation techniques require significant time and labor to arrange simulated hair strands into desired styles while maintaining inherent shape characteristics and clumping effects, and transferring hair styles between characters with different mesh shapes is labor-intensive.

Innovation Solution

A method for manipulating simulated hair strands by identifying consecutive vertex groups and applying displacement vectors while enforcing shape-preserving constraints, and a method for transferring hair styles by mapping root positions and applying rotational matrices to maintain shape and clumping effects across different mesh shapes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If manual vertex-by-vertex manipulation is used to position simulated hair strands, then hair style arrangement can be achieved, but the process becomes extremely time-consuming and labor-intensive

Engineering Contradiction:
Improveease of hair stylingVSAvoidtime for hair styling
Core Design Contradiction:
Ease of operationVSLoss of time

Solution Approach 1:

The patent segments hair strands into multiple vertices along each strand, allowing selective manipulation of specific vertex groups rather than individual vertices. This segmentation enables efficient styling by operating on manageable portions of hair strands while preserving overall strand integrity and inherent characteristics.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent copies inherent shape characteristics from reference hair strands and applies them to target strands through constraint enforcement. By copying and transferring shape properties rather than manually recreating them, the system dramatically reduces styling time while maintaining natural hair appearance.

Inventive Principle:
Principle #26Copying

2Manufacturing precision

If manual manipulation is used to maintain inherent shape characteristics of hair strands, then shape preservation can be achieved, but the process becomes extremely labor-intensive

Engineering Contradiction:
Improveshape preservation accuracyVSAvoidcomplexity of manipulation process
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback through constraint enforcement mechanisms that continuously monitor and maintain inherent shape characteristics during manipulation. The system provides automatic feedback loops that adjust vertex positions to preserve curl patterns, waves, and other inherent properties without requiring manual intervention for each adjustment.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

Hair strands automatically maintain their inherent shape characteristics through self-enforcing constraints embedded in the simulation system. The strands self-correct during manipulation to preserve their natural properties, eliminating the need for artists to manually maintain shape characteristics on each vertex.

Inventive Principle:
Principle #25Self-service

3Manufacturing precision

If clumping effects are manually maintained during hair repositioning, then natural hair appearance can be preserved, but the process becomes very time-consuming

Engineering Contradiction:
Improveclumping effect accuracyVSAvoidhair styling speed
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The patent merges multiple hair strands into clumps as collective units, allowing artists to manipulate entire groups of strands simultaneously rather than individually. This merging enables efficient maintenance of natural clumping effects while dramatically increasing styling productivity through batch operations.

Inventive Principle:
Principle #5Merging (Combining)

4Adaptability or versatility

If hair styles are transferred between characters with different mesh shapes using prior art techniques, then style transfer can be achieved, but significant time and labor are required

Engineering Contradiction:
Improvehair style transfer capabilityVSAvoidstyle transfer efficiency
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent changes the parameter space by representing hair styles in terms of vertex positions and shape constraints that can be mathematically transformed between different character meshes. This parameter-based approach enables automatic adaptation of hair styles to different mesh shapes through coordinate transformation and constraint adjustment, eliminating manual recalibration.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4309131B1Methods and systems for manipulating and transferring computer-simulated hair
Publication Date: 2026.01.14 DIGITAL DOMAIN VIRTUAL HUMAN US INC
  • EP4309131B1 patent drawingFigure 1
  • EP4309131B1 patent drawingFigure 2
  • EP4309131B1 patent drawingFigure 3

AI summary

A method for manipulating vertex positions of one or more simulated hair strands based on user input while preserving shape details of the one or more simulated hair strands. The method comprises receiving a displacement vector and a region as input and identifying first consecutive groups of vertices of a first simulated hair strand within the region. For each first consecutive group of vertices within the region, the method comprises finding the average vertex position, determining the closest vertex of the consecutive group of vertices to the average vertex position, determining a new positional constraint based on the closest vertex and the displacement vector and determining new vertex positions for the first simulated hair strand by running a constraint enforcement process constrained by the new positional constraint for each consecutive group of vertices and one or more shape-preserving constraints.