# Digital Twin Visualization Skill ## Skill Name digital-twin-visualization ## Purpose Provide expert instruction on creating digital twin simulations for humanoid robots using Gazebo (physics-accurate simulation), Unity (photorealistic visualization), and hybrid Gazebo+Unity workflows for combined physics and visual fidelity. ## When to Use - Student asks about Gazebo simulation setup, world files, or SDF format - Student needs help with Unity URDF import and ROS-TCP-Connector configuration - Student encounters physics simulation issues (robot falling, instability, vibrations) - Student requests guidance on sensor simulation (LiDAR, RGB-D cameras, IMU) in Gazebo - Student asks about hybrid simulation (Gazebo physics + Unity visuals) - Student needs help debugging collision detection or contact parameters ## Inputs - Student question about simulation platforms or configuration - URDF\/SDF files requiring physics tuning - Gazebo world files needing environment design - Unity scenes requiring ROS 2 integration - Physics simulation problems (instability, unrealistic behavior) ## Outputs - Gazebo world file examples with realistic physics - Unity scene setup instructions with ROS-TCP-Connector - Physics parameter tuning guidance (timestep, contact properties, friction) - Sensor plugin configurations (camera, LiDAR, IMU) with noise models - Debugging solutions for common simulation issues - References to Module 2 documentation ## Constraints \/ Boundaries - Focus on Gazebo Fortress\/Classic (compatible with ROS 2 Humble) - Use Unity 2021.3 LTS (long-term support version) - Provide SDF 1.6+ format examples - Follow physics engine best practices (ODE, Bullet, PhysX) - Ensure sensor configurations publish standard ROS 2 message types - Maintain simulation real-time factor ≥0.8 (performance considerations) ## Linked Documentation - `docs\/module2-digital-twin\/gazebo-simulation.md` - Gazebo setup, physics engines, sensor simulation, world creation - `docs\/module2-digital-twin\/unity-integration.md` - Unity setup, URDF import, ROS-TCP-Connector, hybrid simulation - Constitution: Reproducibility, executable code, simulation fidelity standards ## Example Skill Invocation **Student Query**: "My humanoid robot falls through the ground plane in Gazebo. What's wrong?" **Skill Response**: 1. Verify ground plane has collision geometry: `` with `` geometry 2. Check robot spawn height: Ensure `` Z-coordinate ≥1.0m (above ground) 3. Validate URDF inertial properties: Non-zero mass, correct inertia tensors 4. Increase physics solver iterations: `50<\/iterations>` (or higher) 5. Check timestep: `0.001<\/max_step_size>` (1ms recommended) 6. Verify contact parameters: `0.01<\/soft_cfm>`, `0.2<\/soft_erp>` 7. Reference: See `docs\/module2-digital-twin\/gazebo-simulation.md` section "Common Simulation Issues and Solutions"