BrickSim: A Physics-Based Simulator for Manipulating Interlocking Brick Assemblies

2026-03-17

AI Summary

Existing rigid-body simulators struggle to accurately model the snap-fit mechanics of interlocking building blocks, limiting research in contact-rich, long-horizon robotic manipulation. This work presents the first real-time, high-fidelity simulator tailored for interlocking bricks, which innovatively decouples rigid-body dynamics from snap-fit interaction mechanics: a base physics engine (Isaac Sim) handles rigid-body motion, while a compact, custom force model—combined with structured convex quadratic programming—efficiently computes internal snap-fit force distributions. The approach achieves 100% accuracy in predicting static stability across 150 real-world structures, with an average solve time of 5 ms, and faithfully reproduces real fracture behaviors in dynamic drop tests, enabling seamless integration into complex robotic manipulation tasks.

Technology Category

• Intelligent Robots: Manipulation
• Search and Optimization: Sampling/Simulation-based Search
• Computer Vision: Low Level & Physics-based Vision

Application Category

• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Search and Retrieval-Augmented AI: Agentic search

Abstract

Interlocking brick assemblies provide a standardized yet challenging testbed for contact-rich and long-horizon robotic manipulation, but existing rigid-body simulators do not faithfully capture snap-fit mechanics. We present BrickSim, the first real-time physics-based simulator for interlocking brick assemblies. BrickSim introduces a compact force-based mechanics model for snap-fit connections and solves the resulting internal force distribution using a structured convex quadratic program. Combined with a hybrid architecture that delegates rigid-body dynamics to the underlying physics engine while handling snap-fit mechanics separately, BrickSim enables real-time, high-fidelity simulation of assembly, disassembly, and structural collapse. On 150 real-world assemblies, BrickSim achieves 100% accuracy in static stability prediction with an average solve time of 5 ms. In dynamic drop tests, it also faithfully reproduces real-world structural collapse, precisely mirroring both the occurrence of breakage and the specific breakage locations. Built on Isaac Sim, BrickSim further supports seamless integration with a wide variety of robots and existing pipelines. We demonstrate robotic construction of brick assemblies using BrickSim, highlighting its potential as a foundation for research in dexterous, long-horizon robotic manipulation. BrickSim is open-source, and the code is available at https://github.com/intelligent-control-lab/BrickSim.

Problem

• interlocking brick assemblies
• snap-fit mechanics
• robotic manipulation
• physics-based simulation
• rigid-body simulators

Innovation

• snap-fit mechanics
• convex quadratic programming
• hybrid simulation architecture
• real-time physics simulation
• interlocking brick assemblies