Tool for aligning and distribute objects, primarly in 2d space, can be extended to 3d

ObjectSpacing.cs

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

/// <summary>
/// Tool for spacing objects, primarly in 2d space, can be extended to 3d
/// </summary>
public class ObjectSpacing : EditorWindow
{
	[MenuItem ("Hello/ObjectSpacing/Open Window")]
	static void OpenWindow ()
	{
		ObjectSpacing window = (ObjectSpacing)EditorWindow.GetWindow (typeof(ObjectSpacing));
		window.minSize = new Vector2 (100, 30);
		window.Show ();
	}

	Texture[] _icon_distribute;

	Texture[] icon_distribute {
		get { 
			if (_icon_distribute == null) {
				_icon_distribute = new Texture[2];

				_icon_distribute [0] = AssetDatabase.LoadAssetAtPath<Texture2D> ("Assets/Gists/Tools/Editor/distribute-x.png");
				_icon_distribute [1] = AssetDatabase.LoadAssetAtPath<Texture2D> ("Assets/Gists/Tools/Editor/distribute-y.png");
			}

			return _icon_distribute;
		}
	}

	void OnGUI ()
	{
		List<GameObject> objects = new List<GameObject> (Selection.gameObjects);
		int count = objects.Count;

		//GUILayout.Label ("Distribute evenly", EditorStyles.boldLabel);

		GUILayout.BeginHorizontal ();
		EditorGUI.BeginDisabledGroup (count < 2);

		for (int axis = 0; axis < 2; ++axis) {

			GUILayout.BeginVertical ();

			EditorGUILayout.LabelField (" " + GetInterval(axis, objects), GUILayout.MaxWidth (60));

			if (icon_distribute [axis] == null) {
				if (GUILayout.Button (axisName [axis].ToString(), GUILayout.MaxWidth (28))) {
					DistributeByAxis (axis);
				}
			} else {
				if (GUILayout.Button (icon_distribute [axis], GUILayout.MaxWidth (28))) {
					DistributeByAxis (axis);
				}
			}

			GUILayout.EndVertical ();
		}

		//GUILayout.Label ("Distribute by number", EditorStyles.boldLabel);

		GUILayout.BeginHorizontal ();
		for (int axis = 0; axis < 2; ++axis) {
			GUILayout.BeginVertical ();

			//if (axis == 0) {
				alignment [axis] = GUILayout.HorizontalSlider (alignment [axis], 0, 1);
//			} else {
//				alignment [axis] = GUILayout.VerticalSlider (alignment [axis], 1, 0);
//			}

			distance [axis] = EditorGUILayout.FloatField (distance [axis]);
			if (GUILayout.Button ("Spread " + axisName [axis])) {
				DistributeByAxis (axis, distance [axis], alignment [axis]);
			}
			GUILayout.EndVertical ();
		}
		GUILayout.EndHorizontal ();

		EditorGUI.EndDisabledGroup ();
		GUILayout.EndHorizontal ();

	}

	Vector3 alignment = Vector3.zero;

	float GetInterval(int axis, List<GameObject> objects){
		int count = objects.Count;
		if (count < 2)
			return 0;
		
		objects.Sort ((a, b) => a.transform.position [axis].CompareTo (b.transform.position [axis]));
		float min = objects [0].transform.position [axis];
		float max = objects [count - 1].transform.position [axis];
		float interval = (max - min) / (float)(count - 1);
		return interval;
	}

	static string axisName = "xyz";

	Vector3 distance = Vector3.one * 10;

	[MenuItem ("Hello/ObjectSpacing/Vertical")]
	static void SpaceVertical ()
	{
		DistributeByAxis (1);
	}

	[MenuItem ("Hello/ObjectSpacing/Horizontal")]
	static void SpaceHorizontal ()
	{
		DistributeByAxis (0);
	}

	[MenuItem ("Hello/ObjectSpacing/Vertical And Horizontal")]
	static void SpaceVerticalAndHorizontal ()
	{
		DistributeByAxis (0);
		DistributeByAxis (1);
	}

	static void DistributeByAxis (int axis)
	{
		List<GameObject> objects = new List<GameObject> (Selection.gameObjects);
		int count = objects.Count;
		if (count < 2)
			return;
		
		Undo.RecordObjects (Selection.gameObjects, "ObjectSpacing axis " + axis);

		objects.Sort ((a, b) => a.transform.position [axis].CompareTo (b.transform.position [axis]));

		float min = objects [0].transform.position [axis];
		float max = objects [count - 1].transform.position [axis];
		float interval = (max - min) / (float)(count - 1);
		//Debug.Log ("Count " + count);
		for (int i = 0; i < count; ++i) {
			var p = objects [i].transform.position;
			p [axis] = min + (i * interval);
			objects [i].transform.position = p;
		}
	}

	static void DistributeByAxis (int axis, float interval, float align)
	{
		List<GameObject> objects = new List<GameObject> (Selection.gameObjects);
		int count = objects.Count;
		if (count < 2)
			return;

		objects.Sort ((a, b) => a.transform.position [axis].CompareTo (b.transform.position [axis]));
		Undo.RecordObjects (Selection.gameObjects, "ObjectSpacing axis " + axis);

		float min = objects [0].transform.position [axis];
		float max = objects [count-1].transform.position [axis];

		float alignCenter = Mathf.Lerp (min, max, align);
		float distance = interval * (count - 1);
		float start = alignCenter - distance * (align);

		for (int i = 0; i < count; ++i) {
			var p = objects [i].transform.position;
			p [axis] = start + (i * interval);
			objects [i].transform.position = p;
		}
	}

}