simulation | UCSC OSPO

Network Simulation Bridge • Enabling Interactive Network Models

Wed, 28 Jan 2026 00:00:00 +0000

The Network Simulation Bridge – NSB – is a network co-simulation framework that bridges together applications and network simulators. It enables students, researchers, and developers to prototype their applications and systems on simulated networks. It consists of a message server and client endpoint interfaces which together form a bridge, routing application message payloads through the network simulator. NSB is designed to be extensible through modular interfaces that serve to allow users to contribute new features and modules that suit evolving and emerging use cases. NSB is developed to be application-, network simulator-, and platform-agnostic so that users and developers are empowered to integrate any application front-end with any network simulator back-end, providing versatility and flexibility when used alongside other tools in larger systems and applications.

NSB was created in-house by the Inter-Networking Research Group and is now being developed into a more full-featured open-source tool and ecosystem in partnership with the UCSC OSPO and as part of the NSF Pathways to Enable Open-Source Ecosystems program. In this transition to a more polished and feature-rich product, the next phase of NSB development will involve the engineering of new quality-of-life features, testing and iteration of the core tool itself, and user-centric refinement via implementation in interdisciplinary system models.

Develop a User-Centric Website for NSB

Topics: Web Development Dynamic Updates UX
Skills: web development experience, good communicator, (HTML/CSS), (Javascript)
Difficulty: Moderate
Size: Large
Mentors: Harikrishna Kuttivelil

Develop a clean and welcoming landing page and website for the project. The organization needs to reflect the needs of both users and potential project contributors. This website will be the first impression for people new to the project and should

Specific tasks:

Work with mentors on understanding the context of the project and the expected needs of the users.
Port relevant documentation and tutorials from the repository page, ensuring updates in the repository are reflected in the website.
Study existing open source product websites and draw insights to include in our own design.
Design the structure of the website according to best OS, visual design, and accessibility design practices.
Include visual content that showcases NSB integration and testimonials (if applicable).

Improve the User Experience of NSB

Topics: Software Engineering User-Centric Development Visualization UI/UX Documentation
Skills: package management, toolchain implementation, process automation, technical writing, (visualization), (bash), (Python), (C++)
Difficulty: Moderate
Size: Medium
Mentors: Harikrishna Kuttivelil

Our goal has always been to keep NSB streamlined and out of the way of the users and developers. In line with that, we want our tool to be easily available and installable, and we want the experience of using it to feel minimal and non-intrusive while providing sufficient observability of NSB’s internals for those who want it.

Specific tasks:

Work with mentors and potential users on identifying aspects of the user experience that can refined for better quality-of-life experiences.
Verify and iterate on existing software packaging methods for NSB to ensure that tool setup is stress-free.
Refine and update existing documentation and tutorials to reflect improvements in the setup, installation, and usage processes.
Work with mentors and other contributors to work backwards from what the user wants to see to design the user interface.
Work with other contributors (see below) to develop a Network-in-a-Box experience with NSB.

Create a Network-in-a-Box Experience with NSB

Topics: Software Engineering, Simulation, System Modeling, System Design, Visualization, UI/UX
Skills: software integration and interfacing, toolchain implementation, process automation, C++, (visualization), (LLM-enabled code generation), (technical writing)
Difficulty: Challenging
Size: Large
Mentors: Harikrishna Kuttivelil

NSB was originally designed for networking graduate students to interface with application-layer programs. But since then, there’s been more of an appetite for a simpler network-in-a-box approach that would allow users to quickly deploy baseline or generated network simulations that are ready for use with NSB.

Specific tasks:

Learn how to use one of the major open-source network simulators (ns3 or OMNeT++).
Work with mentors in designing a simpler, minimal user experience of operating NSB.
Develop tools to automatically create network simulations given input parameters (type of network, number of nodes, description of infrastructure).
Create documentation aimed at new users.
Implement or embed network visualizations to enrich the user experience.

Implement Networked System Models to Evaluate Quality of NSB

Topics: System Modeling Simulation System Design Software Development Product Testing
Skills: software integration, good communication, qualitative research, (proficiency in Python and/or C++), (processing scientific and technical literature)
Difficulty: Challenging
Size: Large
Mentors: Harikrishna Kuttivelil

NSB is a relatively new tool and has not been extensively tested outside of the core contributors, who know a bit too much about the tool. We need to better understand what external user and contributor experience will be like, and the best way to do that is to start developing with NSB to build models of connected systems, i.e., sensor networks, smart homes, smart farms, etc.

Specific tasks:

Research academic literature and relevant works to identify relevant distributed applications to model.
Work with mentors and collaborators to plan implementation of selected system models.
Track and report issues and concerns in quality-of-life experiences, critical errors, or difficulties.
Work with mentors and contributors to address issues and concerns.
Refine and update existing documentation and tutorials to reflect improvements in the setup, installation, and usage processes.
Work with other contributors (see below) in reviewing and cross-referencing model implementations.

Model Autonomous Vehicle Networks to Drive New Feature Development in NSB

Topics: System Modeling Simulation System Design Software Development
Skills: requirement-based software design, message parsing interfaces, server-client communication, (proficiency in Python and/or C++), (processing scientific and technical literature)
Difficulty: Challenging
Size: Large
Mentors: Harikrishna Kuttivelil

NSB today serves its named purpose – message relaying. However, modeling complex systems can sometimes involving synchronizing other simulation features, like mobility when dealing with vehivle networks. Implementing a generic layer of being able to synchronize user-defined features across endpoints would be a powerful, enabling feature in NSB. In the process, we may also uncover opportunities for improving the NSB developer experience.

Specific tasks:

Research academic literature and relevant works to identify and design potential autonomous vehicle network models.
Work with mentors and collaborators to iterate on system designs to ensure it serves the purpose of furthering NSB development.
Help mentors design and develop the new feature synchronization feature in NSB, driven by the autonomous vehicle system model.
Develop and iterate feature synchronization, using mobility as the synchronized feature.
Create documentation and tutorials to serve as resources for future users, contributors, and developers.
Work with other contributors (see above) in reviewing and cross-referencing model implementations.

Scenic-RoboSuite Integration: Building the First Working Prototype

Mon, 29 Sep 2025 00:00:00 +0000

I’m Sahil, presenting the first working prototype of the Scenic-RoboSuite integration. This project is being mentored by Daniel Fremont and Eric Vin.

After months of development, we have achieved a functional prototype of the Scenic-RoboSuite interface. Researchers can now write basic declarative robotic manipulation scenarios in Scenic that execute with physics simulation in RoboSuite. While still in development, the prototype demonstrates the feasibility and potential of bridging probabilistic scenario generation with detailed robot control.

Major Achievements

MJCF XML Injection

The interface introduces direct MJCF XML support, allowing Scenic to build RoboSuite-native manipulable objects from raw XML definitions. Users can define custom objects with complex mesh geometries, textures, and physics properties directly in their Scenic scenarios:

dragon_xml = '''
<mujoco>
 <asset>
 <mesh file="dragon.stl" scale="0.01 0.01 0.01"/>
 <texture file="dragon_texture.png"/>
 </asset>
 <worldbody>
 <body name="object">
 <geom mesh="dragon_mesh" type="mesh"/>
 </body>
 </worldbody>
</mujoco>
'''

dragon = new CustomObject with mjcfXml dragon_xml

The system automatically handles collision geometry generation, joint creation for physics, and asset file resolution.

Complex Mesh Object Support

Import and manipulate arbitrary 3D models (STL, OBJ) with automatic mesh repair and texture mapping. The interface resolves file paths relative to Scenic files, copies assets to temporary directories for MuJoCo, and converts textures (JPG to PNG) when needed. This enables using custom robotic tools, industrial parts, or any 3D model in manipulation scenarios.

Custom Arena Definition

Define complete custom environments using MJCF XML, extending beyond RoboSuite’s built-in arenas:

custom_arena = new CustomArena with arenaXml localPath("warehouse.xml")

This allows creating specialized workspaces, factory floors, or research-specific environments while maintaining full physics simulation.

Multi-Robot Support

The interface handles multiple robots operating in the same workspace:

robot1 = new Panda at (-0.5, 0, 0)
robot2 = new UR5e at (0.5, 0, 0)
table = new Table at (0, 0, 0.425)

Each robot maintains independent control and can execute coordinated or individual behaviors.

Built-in Manipulation Behaviors

Ready-to-use behaviors for immediate testing and development:

MoveToPosition - Precise end-effector positioning
PickObject - Automated grasping with approach and closure
LiftToHeight - Controlled lifting to target heights
PickAndLift - Complete pick-and-place sequence

These behaviors use Operational Space Control (OSC) for intuitive 3D movement commands.

Extended Environment Configuration

The interface extends RoboSuite’s configurability through Scenic’s parameter system:

param controller_config = {'type': 'OSC_POSITION', 'impedance': 'low'}
param camera_view = 'robot0_eye_in_hand'
param lite_physics = True # Faster simulation for testing

Example: Probabilistic Pick-and-Place

model scenic.simulators.robosuite.model

# Randomly position cube on table
table = new Table at (0.6, 0, 0.425)
cube = new Box on table,
 with color (1, 0, 0, 1),
 with position (Uniform(-0.2, 0.2), Uniform(-0.2, 0.2), _)

# Robot adapts to random cube position
behavior AdaptivePickup():
 do PickAndLift(cube, height=1.1)

ego = new Panda at (0, 0, 0),
 with behavior AdaptivePickup()

Each scenario run generates a different cube position, testing the robot’s adaptive capabilities.

Challenges Overcome

Understanding Dual Architecture Paradigms

RoboSuite and Scenic operate on fundamentally different principles. RoboSuite builds environments imperatively through MuJoCo XML composition, expecting complete scene specification upfront. Scenic generates scenes probabilistically through constraint solving, requiring geometric knowledge before simulation. Bridging these required developing a two-pass system where we first extract geometry from a temporary RoboSuite environment, update Scenic’s understanding, then create the final simulation. This architectural mismatch touched every aspect of the integration, from object creation to property updates.

Discovering and Extending ManipulationEnv

RoboSuite’s documentation focuses on using pre-built tasks, not creating custom environments. Through extensive source code analysis, we discovered that ManipulationEnv was the key - it accepts robots as configuration while allowing customizable arenas and objects as components. This class became our foundation, but required significant extension. We implemented ScenicManipulationEnv to intercept Scenic’s object configurations, handle dynamic arena selection (EmptyArena vs MultiTableArena based on scene content), and manage the complex initialization sequence where robots, arenas, and objects must be assembled in specific order for MuJoCo compilation.

XML to 3D Mesh Pipeline

Converting MJCF XML to usable 3D meshes proved complex. MuJoCo uses XML to describe geometry, but Scenic needs actual mesh data for collision checking. We built a multi-stage pipeline: First, ElementTree parses the XML to extract mesh references and primitive definitions. Then, we handle two paths - for mesh files, we load STL/OBJ files with trimesh and apply XML-specified transformations; for primitives (boxes, cylinders), we generate meshes programmatically. The challenge intensified with composite objects - a table might have a box tabletop and four cylinder legs. We developed ComponentExtractor to analyze the MuJoCo scene graph, identify related geometries through naming patterns and hierarchy, and export each component as a separate GLB file with proper world transforms preserved.

File Path Resolution Discrepancies

Scenic and RoboSuite handle file paths completely differently. Scenic uses localPath() for paths relative to the scenario file, while RoboSuite expects paths relative to its package structure or absolute paths. MJCF XML compounds this - mesh references can be relative to the XML file location, not the calling code. We implemented a sophisticated path resolution system: detect whether paths come from embedded XML (relative to Scenic file) or external XML files (relative to XML location), copy all referenced assets (meshes, textures) to temporary directories accessible to MuJoCo, and handle texture format conversion (JPG to PNG) when needed. This system transparently manages assets whether they’re in the Scenic project, RoboSuite package, or absolute paths, making the interface truly portable.

Impact and Applications

This bridge enables:

Research: Generate diverse manipulation scenarios for robot learning algorithms
Testing: Validate robotic systems against probabilistic task variations
Development: Rapid prototyping of manipulation tasks without manual scene setup
Education: Teach robotics concepts through declarative scenario specification

The integration makes complex robotic simulations accessible through Scenic’s intuitive language while preserving RoboSuite’s detailed physics and control capabilities.

Documentation and Resources

The project includes:

example scenarios demonstrating all features
Comprehensive STATUS.md tracking working features and known issues
Technical documentation in docs/ covering architecture and troubleshooting
Mesh extraction utilities for pre-processing and caching

Current Status and Future Work

This prototype demonstrates that the Scenic-RoboSuite bridge is viable and functional. Basic features are working reliably:

Single-robot manipulation scenarios execute successfully
MJCF XML injection creates custom objects
Pick-and-place behaviors operate consistently
Multi-robot support functions in controlled scenarios

However, significant work remains:

Stability improvements: Some features work intermittently and need refinement
Velocity tracking: Full implementation awaits framework updates
Multi-robot coordination: Advanced synchronization primitives needed
Performance optimization: Mesh extraction and caching can be streamlined
Extended testing: More diverse scenarios and edge cases need validation

The prototype serves as a proof of concept, showing that probabilistic scenario specification can successfully drive physics-based robot simulation. The architecture is sound, the core features function, and the path forward is clear.

Conclusion

This working prototype of the Scenic-RoboSuite integration represents significant progress toward bridging probabilistic programming with robotic simulation. We’ve successfully demonstrated that declarative scenario specification can control detailed physics simulation, opening new possibilities for robotic system development and testing.

While not yet production-ready, the prototype provides a solid foundation for future development. Researchers can begin experimenting with basic manipulation scenarios, developers can test the interface with their use cases, and the community can contribute to making this bridge more robust and feature-complete.

The challenges overcome - from understanding dual architectures to implementing XML-to-mesh pipelines - have resulted in a functional system that validates our approach. This prototype proves that Scenic’s elegant scenario language and RoboSuite’s detailed physics can work together, setting the stage for a powerful new tool in robotics research and development.

Robot Manipulation with Scenic-RoboSuite

Wed, 30 Jul 2025 00:00:00 +0000

We’re Sahil, continuing work on the Scenic-RoboSuite integration for GSoC 2025. This project is mentored by Daniel Fremont and Eric Vin.

Since the last update, the Scenic-RoboSuite interface has made significant progress. The bidirectional bridge is now functional - robots can read sensor data and execute behaviors based on observations. However, these features are still in early stages and we’re working on making them more stable and consistent.

We’ve integrated RoboSuite’s Operational Space Control into Scenic. This control method lets you command the robot’s hand directly in 3D space (like “move 10cm left”) instead of calculating complex joint rotations. While the integration works, it’s rough around the edges and we’re currently focused on stabilizing it across different scenarios.

The main challenge was architectural - RoboSuite expects all robot commands bundled together each timestep, while Scenic processes them one by one. We solved this with a pending actions system that collects everything first, then executes in one go. Time synchronization was another challenge, matching Scenic’s steps with MuJoCo’s physics.

We’ve implemented a basic pick-and-place behavior for basic testing. The robot reads sensor data, calculates where to move, and adjusts continuously. It can successfully grasp and lift objects, though consistency varies between runs. The system supports three robot models and works with RoboSuite’s pre-built environments.

Custom world building is currently on hold. We’ve decided to focus on integrating existing RoboSuite features into Scenic first, then build Scenic’s capabilities like dynamic scenario randomization on top. For our first prototype, we’re aiming to extend the pick-and-place behavior into a full randomization demo - Scenic will randomly position the cube each run, and the robot will adapt to find and grasp it regardless of location.

The next two weeks focus on stabilizing current features and preparing this randomized scenario prototype. Expanding the behavior library and supporting additional environments will come in future phases after we have a solid foundation.

The core bridge between Scenic and RoboSuite is operational, but there’s significant work ahead to make it reliable and user-friendly.

Introducing Scenic-RoboSuite Interface

Sun, 15 Jun 2025 00:00:00 +0000

Hey! I’m Sahil, working on integrating Scenic with RoboSuite for GSoC 2025. My project is mentored by Daniel Fremont and Eric Vin .

I’m connecting Scenic (a probabilistic programming language for scenarios) with RoboSuite (a robotics simulation framework). Basically, you write simple scenario descriptions and get complex 3D robot simulations automatically.

Currently, as I’m building things and learning how Scenic works, I have been able to get the basic skeleton for the simulator interface working. I’ve implemented the simulator class and built a world model that can translate Scenic objects into RoboSuite’s simulator (which is MuJoCo-based). The interface now handles precise object placement in the world pretty well.

One of the trickier parts was figuring out the translation logic between Scenic and RoboSuite. I managed to overcome this by building a system that automatically detects the shape of objects when moving between the two frameworks, which lays a foundation for more complex object mapping later on.

I’ve also built some basic example scenarios to run and test with. Currently working on more complex examples and testing Scenic’s features like probabilistic object placement, constraint satisfaction, and spatial relationships between objects.

In summary, the “Scenic to RoboSuite” part of the interface is pretty much done. For next week, I need to work on the “RoboSuite to Scenic” part - basically getting feedback and state information flowing back from the simulation. Achieving this will make a complete bridge and give us a working simulator interface, which is the first major milestone for the project.