RandomTexture.cs

using System.Collections;
using UnityEngine;

namespace Sorter
{
    [RequireComponent(typeof(MeshRenderer))]
    public class RandomTexture : MonoBehaviour
    {
        [SerializeField] private Vector2Int textureDimension = new Vector2Int(128, 128);

        private Color32[] colors;
        private float[] hues;
        private float[] values;
        private Material material;
        private Texture2D texture;

        private void Start()
        {
            Random.InitState(123123132);
            RandomizeTexture();
        }

        private void RandomizeTexture()
        {
            material = GetComponent<MeshRenderer>().material;
            texture = new Texture2D(textureDimension.x, textureDimension.y)
            {
                filterMode = FilterMode.Point,
                wrapMode = TextureWrapMode.Clamp
            };
            var pixels = textureDimension.x * textureDimension.y;
            colors = new Color32[pixels];
            hues = new float[pixels];
            values = new float[pixels];
            for (var i = colors.Length - 1; i >= 0; i--)
            {
                hues[i] = Random.value;
                values[i] = Random.value;
                colors[i] = Color.HSVToRGB(hues[i], 1, values[i]);
            }

            UpdateTexture();

            StartCoroutine(SortTexture());
        }

        private IEnumerator SortTexture()
        {
            var width = texture.width;
            var height = texture.height;
            yield return null;

            var timeStart = Time.time;

            for (var b = 0; b < width - 1; b++)
            {
                var changed = false;
                for (var y = 0; y < height; y++)
                {
                    var ibase = y * width;
                    for (var x0 = 0; x0 < width - 1; x0++)
                    {
                        var i0 = x0 + ibase;
                        for (var x1 = x0 + 1; x1 < width; x1++)
                        {
                            var i1 = x1 + ibase;
                            if (hues[i1] >= hues[i0]) continue;

                            (hues[i0], hues[i1]) = (hues[i1], hues[i0]);
                            (values[i0], values[i1]) = (values[i1], values[i0]);
                            (colors[i0], colors[i1]) = (colors[i1], colors[i0]);
                            changed = true;
                        }
                    }
                }

                UpdateTexture();
                yield return null;

                for (var x = 0; x < width; x++)
                {
                    for (var y0 = 0; y0 < height - 1; y0++)
                    {
                        var i0 = y0 * width + x;
                        for (var y1 = y0 + 1; y1 < height; y1++)
                        {
                            var i1 = y1 * width + x;
                            if (values[i1] >= values[i0]) continue;

                            (hues[i0], hues[i1]) = (hues[i1], hues[i0]);
                            (values[i0], values[i1]) = (values[i1], values[i0]);
                            (colors[i0], colors[i1]) = (colors[i1], colors[i0]);
                            changed = true;
                        }
                    }
                }

                UpdateTexture();
                yield return null;
                
                if (!changed)
                {
                    Debug.Log($"Breaking at {b} / {width - 1} because of stable solution");
                    break;
                }
            }

            var timeEnd = Time.time;

            Debug.Log($"Sorting complete in {timeEnd - timeStart} seconds");
        }

        private void UpdateTexture()
        {
            texture.SetPixels32(colors);
            texture.Apply();
            material.mainTexture = texture;
        }
    }
}