Activate physics in Edit mode to dynamically drop or settle objects in a scene

PhysicsSettler.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.ShortcutManagement;

namespace PixelWizards.Utilities
{

    // This causes the class' static constructor to be called on load and on starting playmode
    [InitializeOnLoad]
    class PhysicsSettler
    {
        // only ever register once
        static bool registered = false;

        // are we actively settling physics in our scene
        static bool active = false;

        // the work list of rigid bodies we can find loaded up
        static Rigidbody[] workList;

        // we need to disable auto simulation to manually tick physics
        static bool cachedAutoSimulation;

        // how long do we run physics for before we give up getting things to sleep
        const float timeToSettle = 10f;

        // how long have we been running
        static float activeTime = 0f;

        // this is the static constructor called by [InitializeOnLoad]
        static PhysicsSettler()
        {
            if (!registered)
            {
                // hook into the editor update
                EditorApplication.update += Update;

                // and the scene view OnGui
                SceneView.duringSceneGui += OnSceneGUI;
                registered = true;
            }
        }

        // let users turn on 
        [MenuItem("Edit/Settle Physics")]
#if UNITY_2019_1_OR_NEWER
        [Shortcut("Edit/Settle Physics", KeyCode.Q, ShortcutModifiers.Action | ShortcutModifiers.Alt)]
#endif
        static void Activate()
        {
            if (!active)
            {
                active = true;

                // Normally avoid Find functions, but this is editor time and only happens once
                workList = Object.FindObjectsOfType<Rigidbody>();

                // we will need to ensure autoSimulation is off to manually tick physics
                cachedAutoSimulation = Physics.autoSimulation;
                activeTime = 0f;

                // make sure that all rigidbodies are awake so they will actively settle against changed geometry.
                foreach (Rigidbody body in workList)
                {
                    body.WakeUp();
                }
            }
        }

        // grey out the menu item while we are settling physics
        [MenuItem("Edit/Settle Physics", true)]
        static bool checkMenu()
        {
            return !active;
        }

        static void Update()
        {
            if (active)
            {
                activeTime += Time.deltaTime;

                // make sure we are not autosimulating
                Physics.autoSimulation = false;

                // see if all our 
                bool allSleeping = true;
                foreach (Rigidbody body in workList)
                {
                    if (body != null)
                    {
                        allSleeping &= body.IsSleeping();
                    }
                }

                if (allSleeping || activeTime >= timeToSettle)
                {
                    Physics.autoSimulation = cachedAutoSimulation;
                    active = false;
                }
                else
                {
                    Physics.Simulate(Time.deltaTime);
                }
            }
        }

        static void OnSceneGUI(SceneView sceneView)
        {
            if (active)
            {
                Handles.BeginGUI();
                Color cacheColor = GUI.color;
                GUI.color = Color.red;
                GUILayout.Label("Simulating Physics.", GUI.skin.box, GUILayout.Width(200));
                GUILayout.Label(string.Format("Time Remaining: {0:F2}", (timeToSettle - activeTime)), GUI.skin.box, GUILayout.Width(200));
                Handles.EndGUI();

                foreach (Rigidbody body in workList)
                {
                    if (body != null)
                    {
                        bool isSleeping = body.IsSleeping();
                        if (!isSleeping)
                        {
                            GUI.color = Color.green;
                            Handles.Label(body.transform.position, "SIMULATING");
                        }
                    }
                }
                GUI.color = cacheColor;
            }
        }
    }
}