PhysicsSimulationWindow

// Save this class inside a folder called "Editor" (without quotation you know)
// and also the file MUST be called PhysicsSimulationWindow.cs

using UnityEngine;
using UnityEditor;
using System.Collections.Generic;
using UnityEditor.SceneManagement;

public class PhysicsSimulationWindow : EditorWindow
{
    private bool isSimulating = false;
    private float simulationTime = 0f;
    private float simulationDuration = 5f;
    private SimulationMode originalSimulationMode;
    private List<GameObject> selectedObjects = new List<GameObject>();
    private List<Rigidbody> addedRigidbodies = new List<Rigidbody>();
    private Vector2 scrollPosition;

    [MenuItem("Tools/Physics Simulation")]
    public static void ShowWindow()
    {
        GetWindow<PhysicsSimulationWindow>("Physics Simulation");
    }

    private void OnEnable()
    {
        Selection.selectionChanged += Repaint;
    }

    private void OnDisable()
    {
        Selection.selectionChanged -= Repaint;
    }


    private void OnGUI()
    {
        UpdateSelectedObjects();

        GUILayout.Label("Selected Objects", EditorStyles.boldLabel);

        if (IsPrefabMode())
        {
            EditorGUILayout.HelpBox("Physics simulation is not available in the prefab editor. Please return to the main scene.", MessageType.Warning);
            return;
        }

        EditorGUI.BeginDisabledGroup(isSimulating);
        simulationDuration = EditorGUILayout.FloatField("Simulation Time:", simulationDuration);
        EditorGUI.EndDisabledGroup();

        if (GUILayout.Button(isSimulating ? "Stop Simulation" : "Start Simulation"))
        {
            if (isSimulating)
            {
                StopSimulation();
            }
            else
            {
                StartSimulation();
            }
        }

        if (isSimulating)
        {
            EditorGUILayout.LabelField($"Simulation Time: {simulationTime:F2}s / {simulationDuration:F2}s");
        }

        GUILayout.Space(10);
        GUILayout.Label("Selected Objects:", EditorStyles.boldLabel);

        scrollPosition = EditorGUILayout.BeginScrollView(scrollPosition, GUILayout.Height(150));
        foreach (var obj in selectedObjects)
        {
            EditorGUILayout.ObjectField(obj, typeof(GameObject), true);
        }
        EditorGUILayout.EndScrollView();
    }

    private void UpdateSelectedObjects()
    {
        selectedObjects.Clear();
        selectedObjects.AddRange(Selection.gameObjects);
    }

    private bool IsPrefabMode()
    {
        return PrefabStageUtility.GetCurrentPrefabStage() != null;
    }

    private void StartSimulation()
    {
        if (isSimulating || IsPrefabMode()) return;

        selectedObjects.Clear();
        addedRigidbodies.Clear();
        selectedObjects.AddRange(Selection.gameObjects);

        if (selectedObjects.Count == 0)
        {
            EditorUtility.DisplayDialog("No objects selected", "Select at least one object in the scene.", "OK");
            return;
        }

        foreach (var obj in selectedObjects)
        {
            Rigidbody rb = obj.GetComponent<Rigidbody>();
            if (rb == null)
            {
                rb = Undo.AddComponent<Rigidbody>(obj);
                addedRigidbodies.Add(rb);
            }
        }

        isSimulating = true;
        simulationTime = 0f;
        originalSimulationMode = Physics.simulationMode;
        EditorApplication.update += SimulatePhysics;
    }

    private void StopSimulation()
    {
        if (!isSimulating) return;

        isSimulating = false;
        EditorApplication.update -= SimulatePhysics;
        Physics.simulationMode = originalSimulationMode;

        foreach (var rb in addedRigidbodies)
        {
            if (rb != null)
            {
                Undo.DestroyObjectImmediate(rb);
            }
        }
        addedRigidbodies.Clear();

        SceneView.RepaintAll();
    }

    private void SimulatePhysics()
    {
        if (!isSimulating) return;

        Physics.simulationMode = SimulationMode.Script;
        Physics.Simulate(Time.fixedDeltaTime);

        simulationTime += Time.fixedDeltaTime;
        SceneView.RepaintAll();

        if (simulationTime >= simulationDuration)
        {
            StopSimulation();
        }

        Repaint();
    }

    private void OnDestroy()
    {
        if (isSimulating)
        {
            StopSimulation();
        }
    }
}