BrickSim: A Physics-Based Simulator for Manipulating Interlocking Brick Assemblies
2026-03-17 • Robotics
RoboticsGraphics
AI summaryⓘ
The authors created BrickSim, a new simulator that realistically mimics how interlocking bricks like LEGO snap together and come apart. Unlike other simulators, BrickSim models the special forces involved in these snap-fit connections, making it very accurate and fast. It can predict when brick assemblies will hold or break in real life and is built to work with robot systems. This makes BrickSim useful for teaching robots to build things with these bricks over a long time. The software is open-source and available online.
interlocking brickssnap-fit mechanicsphysics simulationconvex quadratic programmingrigid-body dynamicsrobotic manipulationstructural stabilityIsaac Simreal-time simulationopen-source software
Authors
Haowei Wen, Ruixuan Liu, Weiyi Piao, Siyu Li, Changliu Liu
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.