Webots is an open-source robot simulator providing a complete environment for modeling, programming, and simulating robots. It consists of a C++ Qt-based main application (src/webots) that manages 3D rendering via the custom WREN engine (src/wren), physics simulation via a forked ODE engine (src/ode) with fluid dynamics extensions, and a multi-language controller API (C, C++, Python, Java, MATLAB) in src/controller. The repository includes a vast library of reusable robot models, sensors, actuators, objects, vehicles, and environments under projects/, as well as extensive documentation (docs/) and a web-based streaming interface (resources/web/wwi). The architecture is modular: the simulation world is defined in VRML-based .wbt files, robots are instantiated from PROTO definitions, and controllers run as separate processes communicating via shared memory. Webots supports ROS integration, SUMO traffic simulation, and OpenStreetMap import. The project is actively maintained with comprehensive CI/CD, test suites, and packaging scripts.
Genesis is a universal physics engine designed for robotics and physical AI simulation. It provides a unified multi-physics framework supporting rigid-body dynamics, finite element method (FEM), material point method (MPM), position-based dynamics (PBD), smoothed particle hydrodynamics (SPH), and incremental potential contact (IPC) coupling. The engine is GPU-accelerated via a custom compiler (Quadrants, forked from Taichi) and scales from single-CPU laptops to multi-GPU datacenters. It features differentiable simulation with gradient tape and manual backward passes, enabling end-to-end optimization through physics. The architecture follows a scene-entity-solver pattern with pydantic-based options for configuration, a plugin-based sensor system (cameras, IMU, tactile, lidar, etc.), and multiple rendering backends (rasterizer, raytracer, batch renderer). Robotics-specific features include URDF/MJCF/USD asset import, inverse kinematics, PD control, and reinforcement learning integration via rsl-rl. The codebase is well-structured with extensive tests, CI/CD pipelines, and a large set of examples covering manipulation, locomotion, deformables, fluids, and coupling scenarios. While the engine is primarily an application library, it also serves as a research platform for differentiable physics and novel simulation techniques.