Improve the runtime texture packer algorithm (#31)

* use a random size for testing pack times to show how truly bad the current algo is

* expand overlap test to include padding and pixel padding

* fixed TestPackTimes on KNI

* also test for whether the padding intersects

* Use a binary tree algorithm for the runtime texture packer

* update changelog and bump version

* fixed fna compile errors

* save TestPackTimes textures separately

CHANGELOG.md

@@ -2,7 +2,7 @@
 MLEM tries to adhere to [semantic versioning](https://semver.org/). Potentially breaking changes are written in **bold**.
 
 Jump to version:
-- [7.2.0](#720-in-development)
+- [8.0.0](#800-in-development)
 - [7.1.1](#711)
 - [7.1.0](#710)
 - [7.0.0](#700)
@@ -16,7 +16,7 @@ Jump to version:
 - [5.1.0](#510)
 - [5.0.0](#500)
 
-## 7.2.0 (In Development)
+## 8.0.0 (In Development)
 
 ### MLEM
 Fixes
@@ -35,6 +35,7 @@ Fixes
 
 ### MLEM.Data
 Improvements
+- **Use a binary tree algorithm for RuntimeTexturePacker to vastly increase packing speed**
 - Made fields and methods in StaticJsonConverter protected to allow extending it
 
 ## 7.1.1

MLEM.Data/RuntimeTexturePacker.cs

@@ -4,7 +4,6 @@ using System.Diagnostics;
 using System.Linq;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
-using MLEM.Maths;
 using MLEM.Textures;
 using static MLEM.Textures.TextureExtensions;
 
@@ -14,6 +13,9 @@ namespace MLEM.Data {
     /// Packing textures in this manner allows for faster rendering, as fewer texture swaps are required.
     /// The resulting texture segments are returned as <see cref="TextureRegion"/> instances.
     /// </summary>
+    /// <remarks>
+    /// The algorithm used by this implementation is based on the blog post "Binary Tree Bin Packing Algorithm", which can be found at https://codeincomplete.com/articles/bin-packing/.
+    /// </remarks>
     public class RuntimeTexturePacker : IDisposable {
 
         /// <summary>
@@ -36,31 +38,21 @@ namespace MLEM.Data {
         /// <summary>
         /// The amount of currently packed texture regions.
         /// </summary>
-        public int PackedTextures => this.packedTextures.Count;
+        public int PackedTextures => this.PackedTexture != null ? this.requests.Count : 0;
 
-        private readonly List<Request> texturesToPack = new List<Request>();
+        private readonly List<Request> requests = new List<Request>();
-        private readonly List<Request> packedTextures = new List<Request>();
-        private readonly Dictionary<Point, Request> occupiedPositions = new Dictionary<Point, Request>();
-        private readonly Dictionary<Point, Point> initialPositions = new Dictionary<Point, Point>();
         private readonly Dictionary<Texture2D, TextureData> dataCache = new Dictionary<Texture2D, TextureData>();
-        private readonly bool autoIncreaseMaxWidth;
         private readonly bool forcePowerOfTwo;
         private readonly bool forceSquare;
         private readonly bool disposeTextures;
 
-        private int maxWidth;
-
         /// <summary>
         /// Creates a new runtime texture packer with the given settings.
         /// </summary>
-        /// <param name="maxWidth">The maximum width that the packed texture can have. Defaults to 2048.</param>
-        /// <param name="autoIncreaseMaxWidth">Whether the maximum width should be increased if there is a texture to be packed that is wider than the maximum width specified in the constructor. Defaults to false.</param>
         /// <param name="forcePowerOfTwo">Whether the resulting <see cref="PackedTexture"/> should have a width and height that is a power of two.</param>
         /// <param name="forceSquare">Whether the resulting <see cref="PackedTexture"/> should be square regardless of required size.</param>
         /// <param name="disposeTextures">Whether the original textures submitted to this texture packer should be disposed after packing.</param>
-        public RuntimeTexturePacker(int maxWidth = 2048, bool autoIncreaseMaxWidth = false, bool forcePowerOfTwo = false, bool forceSquare = false, bool disposeTextures = false) {
+        public RuntimeTexturePacker(bool forcePowerOfTwo = false, bool forceSquare = false, bool disposeTextures = false) {
-            this.maxWidth = maxWidth;
-            this.autoIncreaseMaxWidth = autoIncreaseMaxWidth;
             this.forcePowerOfTwo = forcePowerOfTwo;
             this.forceSquare = forceSquare;
             this.disposeTextures = disposeTextures;
@@ -145,15 +137,7 @@ namespace MLEM.Data {
         /// <param name="padWithPixels">Whether the texture's padding should be filled with a copy of the texture's border, rather than transparent pixels. This value only has an effect if <paramref name="padding"/> is greater than 0.</param>
         /// <exception cref="InvalidOperationException">Thrown when trying to add a texture width a width greater than the defined max width.</exception>
         public void Add(TextureRegion texture, Action<TextureRegion> result, int padding = 0, bool padWithPixels = false) {
-            var paddedWidth = texture.Width + 2 * padding;
+            this.requests.Add(new Request(texture, result, padding, padWithPixels));
-            if (paddedWidth > this.maxWidth) {
-                if (this.autoIncreaseMaxWidth) {
-                    this.maxWidth = paddedWidth;
-                } else {
-                    throw new InvalidOperationException($"Cannot add texture with width {texture.Width} to a texture packer with max width {this.maxWidth}");
-                }
-            }
-            this.texturesToPack.Add(new Request(texture, result, padding, padWithPixels));
         }
 
         /// <summary>
@@ -163,19 +147,32 @@ namespace MLEM.Data {
         /// </summary>
         /// <param name="device">The graphics device to use for texture generation</param>
         public void Pack(GraphicsDevice device) {
-            // set pack areas for each request
+            // set pack areas for each request based on the algo in https://codeincomplete.com/articles/bin-packing/
-            // we pack larger textures first, so that smaller textures can fit in the gaps that larger ones leave
             var stopwatch = Stopwatch.StartNew();
-            foreach (var request in this.texturesToPack.OrderByDescending(t => t.Texture.Width * t.Texture.Height)) {
+            RequestNode root = null;
-                request.PackedArea = this.OccupyFreeArea(request);
+            foreach (var request in this.requests.OrderByDescending(t => Math.Max(t.Texture.Width, t.Texture.Height) + t.Padding * 2)) {
-                this.packedTextures.Add(request);
+                var size = new Point(request.Texture.Width, request.Texture.Height);
+                size.X += request.Padding * 2;
+                size.Y += request.Padding * 2;
+
+                if (root == null)
+                    root = new RequestNode(0, 0, size.X, size.Y);
+
+                var node = RuntimeTexturePacker.FindNode(size, root);
+                if (node == null) {
+                    root = RuntimeTexturePacker.GrowNode(size, root);
+                    node = RuntimeTexturePacker.FindNode(size, root);
+                }
+
+                request.Node = node;
+                node.Split(size);
             }
             stopwatch.Stop();
             this.LastCalculationTime = stopwatch.Elapsed;
 
             // figure out texture size and regenerate texture if necessary
-            var width = this.packedTextures.Max(t => t.PackedArea.Right);
+            var width = root.Area.Width;
-            var height = this.packedTextures.Max(t => t.PackedArea.Bottom);
+            var height = root.Area.Height;
             if (this.forcePowerOfTwo) {
                 width = RuntimeTexturePacker.ToPowerOfTwo(width);
                 height = RuntimeTexturePacker.ToPowerOfTwo(height);
@@ -184,26 +181,24 @@ namespace MLEM.Data {
                 width = height = Math.Max(width, height);
 
             // if we don't need to regenerate, we only need to add newly added regions
-            IEnumerable<Request> texturesToCopy = this.texturesToPack;
             if (this.PackedTexture == null || this.PackedTexture.Width != width || this.PackedTexture.Height != height) {
                 this.PackedTexture?.Dispose();
                 this.PackedTexture = new Texture2D(device, width, height);
-                // if we need to regenerate, we need to copy all regions since the old ones were deleted
-                texturesToCopy = this.packedTextures;
             }
 
             // copy texture data onto the packed texture
             stopwatch.Restart();
             using (var data = this.PackedTexture.GetTextureData()) {
-                foreach (var request in texturesToCopy)
+                foreach (var request in this.requests)
                     this.CopyRegion(data, request);
             }
             stopwatch.Stop();
             this.LastPackTime = stopwatch.Elapsed;
 
             // invoke callbacks for textures we copied
-            foreach (var request in texturesToCopy) {
+            foreach (var request in this.requests) {
-                var packedArea = request.PackedArea.Shrink(new Point(request.Padding, request.Padding));
+                var packedLoc = request.Node.Area.Location + new Point(request.Padding, request.Padding);
+                var packedArea = new Rectangle(packedLoc.X, packedLoc.Y, request.Texture.Width, request.Texture.Height);
                 request.Result.Invoke(new TextureRegion(this.PackedTexture, packedArea) {
                     Pivot = request.Texture.Pivot,
                     Name = request.Texture.Name,
@@ -213,7 +208,6 @@ namespace MLEM.Data {
                     request.Texture.Texture.Dispose();
             }
 
-            this.texturesToPack.Clear();
             this.dataCache.Clear();
         }
 
@@ -225,10 +219,7 @@ namespace MLEM.Data {
             this.PackedTexture = null;
             this.LastCalculationTime = TimeSpan.Zero;
             this.LastPackTime = TimeSpan.Zero;
-            this.texturesToPack.Clear();
+            this.requests.Clear();
-            this.packedTextures.Clear();
-            this.initialPositions.Clear();
-            this.occupiedPositions.Clear();
             this.dataCache.Clear();
         }
 
@@ -237,53 +228,9 @@ namespace MLEM.Data {
             this.Reset();
         }
 
-        private Rectangle OccupyFreeArea(Request request) {
-            var size = new Point(request.Texture.Width, request.Texture.Height);
-            size.X += request.Padding * 2;
-            size.Y += request.Padding * 2;
-
-            // exit early if the texture doesn't need to find a free location
-            if (size.X <= 0 || size.Y <= 0)
-                return Rectangle.Empty;
-
-            var pos = this.initialPositions.TryGetValue(size, out var first) ? first : Point.Zero;
-            var area = new Rectangle(pos.X, pos.Y, size.X, size.Y);
-            var lowestY = int.MaxValue;
-            while (true) {
-                // check if the current area is already occupied
-                if (!this.occupiedPositions.TryGetValue(area.Location, out var existing)) {
-                    existing = this.packedTextures.FirstOrDefault(t => t.PackedArea.Intersects(area));
-                    // if no texture is occupying this space, we have found a free area
-                    if (existing == null) {
-                        // if this is the first position that this request fit in, no other requests of the same size will find a position before it
-                        this.initialPositions[new Point(area.Width, area.Height)] = area.Location;
-                        this.occupiedPositions.Add(area.Location, request);
-                        return area;
-                    }
-
-                    // also cache the existing texture for this position, in case we check it again in the future
-                    this.occupiedPositions.Add(area.Location, existing);
-                }
-
-                // move to the right by the existing texture's width
-                area.X = existing.PackedArea.Right;
-
-                // remember the smallest intersecting texture's height for when we move down
-                if (lowestY > existing.PackedArea.Bottom)
-                    lowestY = existing.PackedArea.Bottom;
-
-                // move down a row if we exceed our maximum width
-                if (area.Right > this.maxWidth) {
-                    area.X = 0;
-                    area.Y = lowestY;
-                    lowestY = int.MaxValue;
-                }
-            }
-        }
-
         private void CopyRegion(TextureData destination, Request request) {
             var data = this.GetCachedTextureData(request.Texture.Texture);
-            var location = request.PackedArea.Location + new Point(request.Padding, request.Padding);
+            var location = request.Node.Area.Location + new Point(request.Padding, request.Padding);
             for (var x = -request.Padding; x < request.Texture.Width + request.Padding; x++) {
                 for (var y = -request.Padding; y < request.Texture.Height + request.Padding; y++) {
                     Color srcColor;
@@ -328,13 +275,57 @@ namespace MLEM.Data {
             return ret;
         }
 
+        private static RequestNode FindNode(Point requestSize, RequestNode node) {
+            if (node.Down != null && node.Right != null) {
+                return RuntimeTexturePacker.FindNode(requestSize, node.Right) ?? RuntimeTexturePacker.FindNode(requestSize, node.Down);
+            } else if (requestSize.X <= node.Area.Width && requestSize.Y <= node.Area.Height) {
+                return node;
+            } else {
+                return null;
+            }
+        }
+
+        private static RequestNode GrowNode(Point requestSize, RequestNode node) {
+            var canGrowDown = requestSize.X <= node.Area.Width;
+            var canGrowRight = requestSize.Y <= node.Area.Height;
+
+            var shouldGrowRight = canGrowRight && node.Area.Height >= node.Area.Width + requestSize.X;
+            var shouldGrowDown = canGrowDown && node.Area.Width >= node.Area.Height + requestSize.Y;
+
+            if (shouldGrowRight) {
+                return RuntimeTexturePacker.GrowNodeRight(requestSize, node);
+            } else if (shouldGrowDown) {
+                return RuntimeTexturePacker.GrowNodeDown(requestSize, node);
+            } else if (canGrowRight) {
+                return RuntimeTexturePacker.GrowNodeRight(requestSize, node);
+            } else if (canGrowDown) {
+                return RuntimeTexturePacker.GrowNodeDown(requestSize, node);
+            } else {
+                return null;
+            }
+        }
+
+        private static RequestNode GrowNodeRight(Point requestSize, RequestNode node) {
+            return new RequestNode(0, 0, node.Area.Width + requestSize.X, node.Area.Height) {
+                Right = new RequestNode(node.Area.Width, 0, requestSize.X, node.Area.Height),
+                Down = node
+            };
+        }
+
+        private static RequestNode GrowNodeDown(Point requestSize, RequestNode node) {
+            return new RequestNode(0, 0, node.Area.Width, node.Area.Height + requestSize.Y) {
+                Right = node,
+                Down = new RequestNode(0, node.Area.Height, node.Area.Width, requestSize.Y)
+            };
+        }
+
         private class Request {
 
             public readonly TextureRegion Texture;
             public readonly Action<TextureRegion> Result;
             public readonly int Padding;
             public readonly bool PadWithPixels;
-            public Rectangle PackedArea;
+            public RequestNode Node;
 
             public Request(TextureRegion texture, Action<TextureRegion> result, int padding, bool padWithPixels) {
                 this.Texture = texture;
@@ -345,5 +336,22 @@ namespace MLEM.Data {
 
         }
 
+        private class RequestNode {
+
+            public readonly Rectangle Area;
+            public RequestNode Down;
+            public RequestNode Right;
+
+            public RequestNode(int x, int y, int width, int height) {
+                this.Area = new Rectangle(x, y, width, height);
+            }
+
+            public void Split(Point requestSize) {
+                this.Down = new RequestNode(this.Area.X, this.Area.Y + requestSize.Y, this.Area.Width, this.Area.Height - requestSize.Y);
+                this.Right = new RequestNode(this.Area.X + requestSize.X, this.Area.Y, this.Area.Width - requestSize.X, requestSize.Y);
+            }
+
+        }
+
     }
 }

Tests/TexturePackerTests.cs

@@ -1,27 +1,25 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using Microsoft.Xna.Framework.Graphics;
 using MLEM.Data;
+using MLEM.Graphics;
+using MLEM.Maths;
 using MLEM.Textures;
 using NUnit.Framework;
+using Color = Microsoft.Xna.Framework.Color;
 
 namespace Tests;
 
 public class TexturePackerTests : GameTestFixture {
 
-    private Texture2D testTexture;
+    private readonly List<TextureRegion> generatedTextures = [];
-    private Texture2D disposedTestTexture;
-
-    [SetUp]
-    public void SetUp() {
-        this.testTexture = new Texture2D(this.Game.GraphicsDevice, 2048, 2048);
-        this.disposedTestTexture = new Texture2D(this.Game.GraphicsDevice, 16, 16);
-    }
 
     [TearDown]
     public void TearDown() {
-        this.testTexture?.Dispose();
+        foreach (var tex in this.generatedTextures)
-        this.disposedTestTexture?.Dispose();
+            tex.Texture.Dispose();
+        this.generatedTextures.Clear();
     }
 
     [Test]
@@ -29,69 +27,67 @@ public class TexturePackerTests : GameTestFixture {
         using var packer = new RuntimeTexturePacker();
         for (var i = 0; i < 5; i++) {
             var width = 16 * (i + 1);
-            packer.Add(new TextureRegion(this.testTexture, 0, 0, width, 64), r => {
+            packer.Add(this.MakeTextureRegion(width, 64), r => {
                 Assert.AreEqual(r.Width, width);
                 Assert.AreEqual(r.Height, 64);
             });
         }
         packer.Pack(this.Game.GraphicsDevice);
-        Assert.AreEqual(packer.PackedTexture.Width, 16 + 32 + 48 + 64 + 80);
+        TexturePackerTests.SaveTexture(packer);
-        Assert.AreEqual(packer.PackedTexture.Height, 64);
+        Assert.AreEqual(packer.PackedTexture.Width, 128);
+        Assert.AreEqual(packer.PackedTexture.Height, 128);
     }
 
     [Test]
-    public void TestOverlap() {
+    public void TestOverlap([Values(0, 1, 5, 10)] int padding) {
         var packed = new List<TextureRegion>();
-        using (var packer = new RuntimeTexturePacker(8192)) {
+        using var packer = new RuntimeTexturePacker();
         for (var i = 1; i <= 1000; i++)
-                packer.Add(new TextureRegion(this.testTexture, 0, 0, i % 239, i % 673), packed.Add);
+            packer.Add(this.MakeTextureRegion(i % 239, i % 673), packed.Add, padding);
         packer.Pack(this.Game.GraphicsDevice);
-        }
+
+        TexturePackerTests.SaveTexture(packer, padding.ToString());
 
         foreach (var r1 in packed) {
+            var r1Padded = r1.Area;
+            r1Padded.Inflate(padding, padding);
+
             foreach (var r2 in packed) {
                 if (r1 == r2)
                     continue;
-                Assert.False(r1.Area.Intersects(r2.Area));
+
+                Assert.False(r1.Area.Intersects(r2.Area), $"Regions {r1.Area} and {r2.Area} intersect");
+
+                var r2Padded = r2.Area;
+                r2Padded.Inflate(padding, padding);
+                Assert.False(r1Padded.Intersects(r2Padded), $"Padded regions {r1Padded} and {r2Padded} intersect");
             }
         }
     }
 
     [Test]
     public void TestDisposal() {
-        using var packer = new RuntimeTexturePacker(128, disposeTextures: true);
+        using var packer = new RuntimeTexturePacker(disposeTextures: true);
-        packer.Add(new TextureRegion(this.disposedTestTexture), TexturePackerTests.StubResult);
+        var disposeLater = this.MakeTextureRegion(16, 16);
-        packer.Add(new TextureRegion(this.disposedTestTexture, 0, 0, 8, 8), TexturePackerTests.StubResult);
+        packer.Add(disposeLater, TexturePackerTests.StubResult);
+        packer.Add(new TextureRegion(disposeLater, 0, 0, 8, 8), TexturePackerTests.StubResult);
         packer.Pack(this.Game.GraphicsDevice);
-        Assert.True(this.disposedTestTexture.IsDisposed);
+        Assert.True(disposeLater.Texture.IsDisposed);
         Assert.False(packer.PackedTexture.IsDisposed);
     }
 
     [Test]
     public void TestBounds() {
-        // test forced max width
-        using var packer = new RuntimeTexturePacker(128);
-        Assert.Throws<InvalidOperationException>(() => {
-            packer.Add(new TextureRegion(this.testTexture, 0, 0, 256, 128), TexturePackerTests.StubResult);
-        });
-
-        // test auto-expanding width
-        using var packer2 = new RuntimeTexturePacker(128, true);
-        Assert.DoesNotThrow(() => {
-            packer2.Add(new TextureRegion(this.testTexture, 0, 0, 256, 128), TexturePackerTests.StubResult);
-        });
-        packer2.Pack(this.Game.GraphicsDevice);
-
         // test power of two forcing
-        using var packer3 = new RuntimeTexturePacker(128, forcePowerOfTwo: true);
+        using var packer3 = new RuntimeTexturePacker(true);
-        packer3.Add(new TextureRegion(this.testTexture, 0, 0, 37, 170), TexturePackerTests.StubResult);
+        packer3.Add(this.MakeTextureRegion(37, 170), TexturePackerTests.StubResult);
         packer3.Pack(this.Game.GraphicsDevice);
         Assert.AreEqual(64, packer3.PackedTexture.Width);
         Assert.AreEqual(256, packer3.PackedTexture.Height);
 
         // test square forcing
-        using var packer4 = new RuntimeTexturePacker(128, forceSquare: true);
+        using var packer4 = new RuntimeTexturePacker(forceSquare: true);
-        packer4.Add(new TextureRegion(this.testTexture, 0, 0, 37, 170), TexturePackerTests.StubResult);
+        packer4.Add(this.MakeTextureRegion(37, 170), TexturePackerTests.StubResult);
         packer4.Pack(this.Game.GraphicsDevice);
         Assert.AreEqual(170, packer4.PackedTexture.Width);
         Assert.AreEqual(170, packer4.PackedTexture.Height);
@@ -99,45 +95,66 @@ public class TexturePackerTests : GameTestFixture {
 
     [Test]
     public void TestPackMultipleTimes() {
-        using var packer = new RuntimeTexturePacker(1024);
+        using var packer = new RuntimeTexturePacker();
 
         // pack the first time
         var results = 0;
         for (var i = 0; i < 10; i++)
-            packer.Add(new TextureRegion(this.testTexture, 0, 0, 64, 64), _ => results++);
+            packer.Add(this.MakeTextureRegion(64, 64), _ => results++);
         packer.Pack(this.Game.GraphicsDevice);
         Assert.AreEqual(10, results);
 
-        // pack without resizing
+        // pack again
-        packer.Add(new TextureRegion(this.testTexture, 0, 0, 0, 0), _ => results++);
+        packer.Add(this.MakeTextureRegion(64, 64), _ => results++);
         packer.Pack(this.Game.GraphicsDevice);
-        Assert.AreEqual(11, results);
+        // all callbacks are called again, so we add 10 again, as well as the callback we just added
-
+        Assert.AreEqual(10 + 10 + 1, results);
-        // pack and force a resize
-        packer.Add(new TextureRegion(this.testTexture, 0, 0, 64, 64), _ => results++);
-        packer.Pack(this.Game.GraphicsDevice);
-        // all callbacks are called again, so we add 11 again, as well as the callback we just added
-        Assert.AreEqual(2 * 11 + 1, results);
     }
 
     [Test]
-    public void TestPackTimes() {
+    public void TestPackTimes([Values(1, 100, 1000, 5000, 10000)] int total) {
-        for (var total = 1; total <= 10001; total += 1000) {
+        var random = new Random(1238492384);
         using var sameSizePacker = new RuntimeTexturePacker();
         using var diffSizePacker = new RuntimeTexturePacker();
         for (var i = 0; i < total; i++) {
-                sameSizePacker.Add(new TextureRegion(this.testTexture, 0, 0, 10, 10), TexturePackerTests.StubResult);
+            sameSizePacker.Add(this.MakeTextureRegion(10, 10), TexturePackerTests.StubResult);
-                diffSizePacker.Add(new TextureRegion(this.testTexture, 0, 0, 10 + i % 129, 10 * (i % 5 + 1)), TexturePackerTests.StubResult);
+            diffSizePacker.Add(this.MakeTextureRegion(random.Next(10, 200), random.Next(10, 200)), TexturePackerTests.StubResult);
         }
         sameSizePacker.Pack(this.Game.GraphicsDevice);
         diffSizePacker.Pack(this.Game.GraphicsDevice);
 
+        TexturePackerTests.SaveTexture(sameSizePacker, $"SameSize{total}");
+        TexturePackerTests.SaveTexture(diffSizePacker, $"DiffSize{total}");
+
         TestContext.WriteLine($"""
             {total} regions,
-                same-size {sameSizePacker.LastCalculationTime.TotalMilliseconds} calc, {sameSizePacker.LastPackTime.TotalMilliseconds} pack, {sameSizePacker.LastTotalTime.TotalMilliseconds} total,
+            same-size {sameSizePacker.LastCalculationTime.TotalMilliseconds}ms calc, {sameSizePacker.LastPackTime.TotalMilliseconds}ms pack, {sameSizePacker.LastTotalTime.TotalMilliseconds}ms total,
-                diff-size {diffSizePacker.LastCalculationTime.TotalMilliseconds} calc, {diffSizePacker.LastPackTime.TotalMilliseconds} pack, {diffSizePacker.LastTotalTime.TotalMilliseconds} total
+            diff-size {diffSizePacker.LastCalculationTime.TotalMilliseconds}ms calc, {diffSizePacker.LastPackTime.TotalMilliseconds}ms pack, {diffSizePacker.LastTotalTime.TotalMilliseconds}ms total
             """);
     }
+
+    private TextureRegion MakeTextureRegion(int width, int height) {
+        var color = ColorHelper.FromHexRgb(SingleRandom.Int(this.generatedTextures.Count));
+        var texture = new Texture2D(this.Game.GraphicsDevice, Math.Max(width, 1), Math.Max(height, 1));
+        using (var data = texture.GetTextureData()) {
+            for (var x = 0; x < texture.Width; x++) {
+                for (var y = 0; y < texture.Height; y++)
+                    data[x, y] = color;
+            }
+        }
+        var region = new TextureRegion(texture, 0, 0, width, height);
+        this.generatedTextures.Add(region);
+        return region;
+    }
+
+    private static void SaveTexture(RuntimeTexturePacker packer, string append = "") {
+        var caller = new System.Diagnostics.StackTrace(1).GetFrame(0).GetMethod().Name + append;
+        var file = Path.GetFullPath(Path.Combine(TestContext.CurrentContext.WorkDirectory, "PackedTextures", caller + ".png"));
+        Directory.CreateDirectory(Path.GetDirectoryName(file)!);
+        using (var stream = File.Create(file))
+            packer.PackedTexture.SaveAsPng(stream, packer.PackedTexture.Width, packer.PackedTexture.Height);
+        TestContext.WriteLine($"Saving texture generated by {caller} to {file}");
+        TestContext.AddTestAttachment(file);
     }
 
     private static void StubResult(TextureRegion region) {}

build.cake

@@ -2,7 +2,7 @@
 #tool dotnet:?package=docfx&version=2.75.3
 
 // this is the upcoming version, for prereleases
-var version = Argument("version", "7.2.0");
+var version = Argument("version", "8.0.0");
 var target = Argument("target", "Default");
 var gitRef = Argument("ref", "refs/heads/main");
 var buildNum = Argument("buildNum", "");
@@ -40,7 +40,7 @@ Task("Test").IsDependentOn("Prepare").Does(() => {
     var settings = new DotNetTestSettings {
         Configuration = config,
         Collectors = {"XPlat Code Coverage"},
-        Loggers = {"console;verbosity=normal"}
+        Loggers = {"console;verbosity=normal", "nunit"}
     };
     DotNetTest("MLEM.sln", settings);
     DotNetTest("MLEM.FNA.sln", settings);