Webots vs. Gazebo: Choosing a Robotics Simulator

Choosing the right robotics simulator can make or break your project timeline and development efficiency. Two simulators consistently emerge as top contenders in the robotics community: Webots and Gazebo. Both offer powerful 3D simulation capabilities, but they cater to different needs and workflows. This comprehensive comparison will help you make an informed decision for your specific robotics application.

As robotics development becomes increasingly complex and costly, simulation has evolved from a nice-to-have tool to an essential component of the development pipeline. The COVID-19 pandemic further accelerated this trend, making simulation tools crucial when access to physical systems became limited.

Overview: Understanding Both Simulators

Webots: The Comprehensive Education-Focused Platform

Webots started in 1996 at the Swiss Federal Institute of Technology (EPFL) and was later developed commercially by Cyberbotics Ltd. Since December 2018, it has been released under the free and open-source Apache 2 license. Webots is known for its user-friendly interface and extensive documentation, which makes it more accessible for novices in robotics.

The simulator provides a complete development environment to model, program, and simulate robots, vehicles, and mechanical systems. It's particularly beginner-friendly software that introduces newcomers to the world of robotics effectively. Webots includes a large collection of freely modifiable models of robots, sensors, actuators, and objects.

Gazebo: The ROS Ecosystem Champion

Gazebo is a three-dimensional open-source robot dynamics simulator created by the Open Source Robotics Foundation. It was designed as a natural complement to the Robot Operating System (ROS), and the Gazebo-ROS combination has become a powerful standard in the robotics community. Gazebo comes installed with a full ROS install and has developed a widespread following among researchers and developers.

The simulator boasts a powerful physics engine and supports multiple physics engines including ODE (Open Dynamics Engine), Bullet, DART, and Simbody. This flexibility allows users to choose the most appropriate physics simulation for their specific applications.

Technical Capabilities and Performance

Physics Simulation Quality

Recent quantitative studies comparing major robotics simulators have provided valuable insights into performance differences. Based on experiments using real Husky A200 mobile robot data as ground truth, researchers concluded that while CoppeliaSim currently ranks as the best performing simulator, Gazebo is not far behind and represents a good alternative.

Webots provides robust physics simulation with customizable environments and supports realistic physics modeling. However, Gazebo's multiple physics engine options give it an edge in scenarios requiring specific physics characteristics.

Computational Requirements

Gazebo is better suited for large-scale simulations and scenarios requiring high computational power, while Webots excels in real-time simulations with moderate computational demands. Webots tends to be more resource-efficient for smaller-scale projects, making it ideal for educational environments and prototyping scenarios.

User Experience and Learning Curve

Interface and Usability

Webots is renowned for its user-friendly interface and comprehensive documentation. The graphical user interface is contemporary and intuitive, facilitating realistic simulation through robust physics engines and OpenGL rendering. New users can quickly navigate through the interface and begin creating simulations without extensive training.

Gazebo, while powerful, can be challenging for beginners due to its complexity and the need for understanding both Gazebo and ROS ecosystems. However, this complexity comes with greater flexibility for advanced users who need fine-grained control over simulation parameters.

Programming Language Support

Webots accommodates various programming languages including C, C++, Python, Java, MATLAB, and ROS, providing developers flexibility to choose the best fit for their specific needs. The robot controller programs can be written outside of Webots using a simple API, making integration with existing codebases straightforward.

Gazebo primarily integrates with C++ and Python through ROS, though it supports other languages through ROS bridges. The tight integration with ROS makes it the natural choice for projects already using the ROS ecosystem.

Ecosystem Integration and Community

ROS Integration

Gazebo's integration with ROS is seamless and comprehensive. It comes pre-installed with full ROS distributions and offers native support for ROS topics, services, and actions. This tight integration makes Gazebo the default choice for ROS-based projects and explains its widespread adoption in the robotics research community.

Webots also supports ROS and ROS 2, with recent versions improving this integration significantly. The webots_ros2 package provides interfaces for various devices and includes support for ROS 2 Iron Irwini. However, the integration requires additional setup steps compared to Gazebo's plug-and-play approach.

Community and Support

Gazebo benefits from a large, active community centered around the ROS ecosystem. The extensive community has created numerous robot models, sensors, and environment worlds. For example, simulation assets including 240 models of mobile robots and subterranean environments were created during DARPA's SubT Challenge Virtual Competition.

Webots maintains an active community with comprehensive documentation and tutorial resources. The robotbenchmark.net website offers free access to robotics benchmarks based on Webots simulations, providing an excellent learning platform for newcomers.

Model Libraries and Extensibility

Pre-built Models and Assets

Webots includes an extensive library of pre-built robot models, sensors, and actuators. Recent releases have added models like the ROS-based ROSbot XL robot from Husarion, various Robotiq grippers, and static animals for simulation environments. Users can also import pre-existing CAD models from software like Blender or URDF files.

Gazebo offers prepared examples of robot models and environment worlds, with an active community continuously creating new assets. The simulator's model database includes a vast collection of robot models ranging from simple mobile robots to complex manipulators and aerial vehicles.

Specific Use Cases and Applications

Educational Applications

Webots excels in educational environments due to its intuitive interface and comprehensive learning resources. The simulator is designed to introduce newcomers to robotics concepts effectively, with step-by-step tutorials and examples. The web-based robotbenchmark.net platform allows students to learn robot control programming through browser-based simulations.

Gazebo, while more complex, provides excellent educational value for advanced robotics courses, particularly those focusing on ROS-based development and multi-robot systems.

Research and Development

For research applications, both simulators offer valuable capabilities. Gazebo's tight ROS integration makes it ideal for research projects requiring complex multi-robot coordination, navigation stacks, and manipulation frameworks. The simulator's plugin architecture enables researchers to implement custom algorithms and test novel approaches.

Webots provides an excellent platform for prototyping and algorithm development, particularly for projects requiring quick iteration and testing. Its real-time simulation capabilities make it suitable for human-robot interaction research and real-time control algorithm development.

Cost and Licensing

Both Webots and Gazebo are now open-source and free to use. Webots transitioned to the Apache 2 license in December 2018, eliminating previous commercial licensing requirements. Gazebo has always been open-source under the Apache 2 license, making it freely available for all use cases.

Making the Right Choice

Choose Webots If:

• You're new to robotics simulation and need an intuitive learning platform

• Your project requires consistent real-time performance

• You need cross-platform compatibility with moderate computational requirements

• Educational applications are your primary focus

• You prefer comprehensive built-in documentation and examples

Choose Gazebo If:

• Your project is already ROS-based or you plan to use ROS

• You need large-scale, computationally intensive simulations

• Multi-robot systems and complex scenarios are requirements

• You have experience with Linux-based development environments

• Research applications requiring extensive customization are your focus

Conclusion

Both Webots and Gazebo offer excellent robotics simulation capabilities. Webots excels as an educational platform with user-friendly interfaces and comprehensive documentation, making it ideal for beginners and smaller-scale projects. Gazebo dominates in ROS-integrated applications and large-scale simulations, preferred by research institutions and companies developing complex systems.

Choose based on your project requirements: Webots for education and rapid prototyping, Gazebo for ROS-based research and production systems. Both simulators continue evolving, ensuring solid foundations for robotics development.

Frequently Asked Questions

1. Can I migrate projects between Webots and Gazebo?

Migration requires significant effort due to different file formats (.wbt vs SDF) and APIs. Both support URDF imports as a common exchange format, but controller code must be rewritten.

2. Which offers better physics accuracy?

Both provide good accuracy. Gazebo performs slightly better in some scenarios due to multiple physics engine options, but differences are often negligible for most applications.

3. How do learning curves compare?

Webots has a gentler learning curve with intuitive interfaces and tutorials. Gazebo requires understanding both simulator and ROS concepts, making it steeper initially but more powerful for advanced use.

4. Which is better for multi-robot simulations?

Gazebo handles multi-robot scenarios better due to scalable architecture and ROS integration. Its distributed computing capabilities make it more suitable for large-scale swarm simulations.

5. Do both support cloud-based simulation?

Yes. Webots offers cloud simulation through webots.cloud with browser access. Gazebo can be deployed on platforms like AWS RoboMaker. Both support headless operation for batch processing.