Upcycling of regular wood trunks and logs using Wave Function Collapse (WFC), Augmented Reality (AR), and Mixed Reality (MR) technologies for circular design

Type

Architecture Design Research

Year

2024 – 2025

Keywords

Upcycling wood
Plastic bottles
Repurposed heat-moldable joinery
Wave function collapse (WFC)
Augmented reality (AR)
Mixed reality (MR)

Abstract

In sustainable building design and construction (SBDC), irregular timber elements — unprocessed logs, forks, and branches — remain significantly underutilised because their complex geometries complicate reconfiguration and generate considerable waste. This study introduces a computational workflow that optimises the upcycling of irregular wood into feasible building components, applying Wave Function Collapse (WFC) as a digital aggregation method to automate the spatial configuration of non-standard elements.

The method integrates 3D scanning, algorithmic aggregation, and Finite Element Analysis (FEA) to assess structural viability and ensure efficient material use. For joinery, a heat-moldable connection method using recycled PET bottles is developed: by leveraging the heat-shrink properties of PET, structurally stable joints form between upcycled wood components without adhesives or mechanical fasteners.

The framework is demonstrated through functional furniture and pavilion-scale architectural prototypes. It advances Computer-Aided Architectural Design (CAAD) and construction techniques through 3D scanning, volumetric design, AI-driven building-scale ideation, and AR- and MR-assisted assembly — showing scalable, accessible solutions for sustainable architecture and circular material reuse. WFC-based aggregation increased material utilisation by an average of 28–35% over conventional milling, while MR guidance lowered the barrier to entry for non-expert builders.

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Completed chair assembled from reclaimed irregular logs and trunks

Figure 1 — From Forked Branches to Voxels

The AA School’s robotically fabricated Wood Chip Barn alongside a voxel-based volumetric design strategy. Both treat irregularity as a design opportunity rather than a defect — one organising organic forked units, the other discrete geometric voxels — framing the “material-first” logic this study builds upon.

Figure 2 — Voxelisation and connection rules

Figure 2 — Voxelisation & Connection Rules

Each scanned wood piece is converted into a discrete voxel grid. ‘Effective regular surfaces’ — flat faces usable as connection points — are detected and labelled (e.g. Top / Bottom). Voxel-centre and closest-point analysis defines complementary connecting surfaces between adjacent blocks.

Figure 3 — Research Design

A structured four-phase workflow: input (material collection and design requirements), the SBDC framework, iterative experiment design across furniture, pavilions and architecture, and the final outputs. Feedback from each experiment refines the techniques applied in subsequent phases.

Figure 4 — Sustainable Building Design & Construction (SBDC)

The full framework linking three systems: the Material Reclamation System (MRS) for collection and cataloguing, the Structure Generation and Assessment System (SGAS) for voxel-based generation and FEA, and the Autonomous Construction System for AR- and MR-assisted fabrication.

Figure 5 — Reclaimed Wood Database

A searchable inventory of reclaimed wood — off-cuts, branches, twigs, sticks, forks, pallets, stumps, trunks and fragments — each element 3D scanned and tagged with geometric profile, species, density, moisture content and a structural quality grade for later retrieval and matching.

Figure 6 — Voxel Size Definition

Comparative voxelisation at 40, 50, 60 and 70 mm. The 50 mm unit gave the optimal balance — an average of 476 voxels at a 29.55% internal fill ratio — and was adopted as the standard packing unit; materials below a 50% face threshold fall within processing-loss tolerance.

Figure 7 — Generative Design Workflow for Chair Typology

Within a 500×500×500 mm bounding box, the volume is decoupled into functional substructures — horizontal seat and vertical legs. A modified Wave Function Collapse algorithm populates the space, selecting and rotating reclaimed wood voxels from the database to satisfy distinct rules for each substructure.

Figure 8 — Structural Validation & Design Iteration via FEA

Each generated chair is tested under a 1.08 kN seat load with fixed feet, against stress, deflection (<5 mm) and buckling (factor >2.0) criteria. Failures feed specific constraints back into the WFC loop — for example enforcing higher-grade elements in critical regions — until a design validates for fabrication.

Figure 9 — MR-Assisted Furniture Assembly

Using a Microsoft HoloLens running Fologram, the chair design is overlaid as a 1:1 hologram in the workspace. A non-expert matches each physical irregular log to its holographic counterpart, with the next component revealed only once the previous one is correctly placed — turning abstract drawings into a tangible, step-by-step process.

Figure 10 — Plastic bottle versus rope joints

Figure 10 — Heat-Shrink PET vs. Rope Joinery

A comparison of binding strategies. Like lashing poles with rope, rings cut from recycled PET bottles encircle a joint — but when heated they shrink and grip the wood’s irregular surfaces, locking components together without adhesives or fasteners while preserving each piece’s original form.

Figure 11 — Plastic heat-moldable joinery process

Figure 11 — Heat-Moldable Joinery Process

The three-stage method: a PET sleeve is positioned around the joint, heated with a heat gun (~300 °C) so it contracts and pulls the wood together, then cooled to re-solidify into a rigid collar. The plastic conforms to grooves and roughness in the timber, gaining strength from the wood’s natural texture.

Figure 12 — AR-assisted pavilion visualisation

Figure 12 — AR-Assisted Design Decision-Making

The pavilion is deployed into an AR environment and viewed at full scale across daylight, evening and urban contexts via mobile devices and a scannable QR code. Full-scale visualisation revealed that an entrance suitable in digital models was spatially constricting in reality, prompting a direct revision to widen the entryway.

Figure 13 — UXSD modules integrated in SBDC

Figure 13 — Integrating UXSD Modules in SBDC

An expanded vision of the framework, folding a User Experience System Design (UXSD) layer — user-centred design and platform development — into the material, structural and construction systems, extending the workflow toward an accessible, community-facing circular-design ecology.