src/code-examples/unity-visualization.cs

using UnityEngine;
using System.Collections.Generic;

public class UnityVisualizationManager : MonoBehaviour
{
    public GameObject robotModelPrefab; // Assign your robot prefab in the inspector
    private GameObject instantiatedRobot;

    // This method could be called to initialize the robot in the scene
    public void InitializeRobot(Vector3 position, Quaternion rotation)
    {
        if (robotModelPrefab != null)
        {
            instantiatedRobot = Instantiate(robotModelPrefab, position, rotation);
            Debug.Log("Robot model initialized in Unity.");
        }
        else
        {
            Debug.LogError("Robot Model Prefab is not assigned!");
        }
    }

    // This method could be used to update joint states from simulation
    public void UpdateRobotJointStates(Dictionary<string, float> jointStates)
    {
        if (instantiatedRobot != null)
        {
            foreach (var jointState in jointStates)
            {
                // Find the corresponding joint in the robot model and update its rotation
                // This is a simplified example; actual implementation would vary based on robot model
                Transform jointTransform = FindDeepChild(instantiatedRobot.transform, jointState.Key);
                if (jointTransform != null)
                {
                    // Example: Apply rotation directly (replace with proper joint control)
                    jointTransform.localRotation = Quaternion.Euler(0, jointState.Value, 0); 
                }
            }
            Debug.Log("Robot joint states updated from simulation data.");
        }
    }

    // Helper to find a child by name deep within the hierarchy
    private Transform FindDeepChild(Transform aParent, string aName)
    {
        Queue<Transform> queue = new Queue<Transform>();
        queue.Enqueue(aParent);
        while (queue.Count > 0)
        {
            var c = queue.Dequeue();
            if (c.name == aName)
                return c;
            foreach(Transform t in c)
                queue.Enqueue(t);
        }
        return null;
    }

    // Example usage (for testing purposes)
    void Start()
    {
        // Example initialization
        // InitializeRobot(Vector3.zero, Quaternion.identity);

        // Example joint state update
        // Dictionary<string, float> testJoints = new Dictionary<string, float>
        // {
        //     { "shoulder_pan_joint", 30.0f },
        //     { "elbow_joint", -45.0f }
        // };
        // UpdateRobotJointStates(testJoints);
    }
}

// TODO: Expand this Unity visualization example to include full digital twin synchronization.
// This would involve:
// 1. Receiving real-time robot state data from an external simulation (e.g., Gazebo via ROS 2 Unity Bridge).
// 2. Accurately visualizing the robot model's pose, joint states, and sensor feedback in Unity.
// 3. Implementing user interaction (e.g., teleoperation) in Unity that can control the external simulation.
// Ensure the example is reproducible and clearly explains setup steps (e.g., Unity project setup,
// ROS 2 Unity Bridge integration, asset import).