Add Points property to OrientedBoundingRectangle

src/cs/MonoGame.Extended/Math/OrientedBoundingRectangle.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using Microsoft.Xna.Framework;
 
@@ -45,6 +46,28 @@ namespace MonoGame.Extended
             Orientation = orientation;
         }
 
+        /// <summary>
+        /// Gets a list of points defining the corner points of the oriented rectangle.
+        /// </summary>
+        public IReadOnlyList<Vector2> Points
+        {
+            get
+            {
+                var topLeft = -Radii;
+                var bottomLeft = -new Vector2(Radii.X, -Radii.Y);
+                var topRight = (Vector2)new Point2(Radii.X, -Radii.Y);
+                var bottomRight = Radii;
+
+                return new List<Vector2>
+                    {
+                        Vector2.Transform(topRight, Orientation) + Center,
+                        Vector2.Transform(topLeft, Orientation) + Center,
+                        Vector2.Transform(bottomLeft, Orientation) + Center,
+                        Vector2.Transform(bottomRight, Orientation) + Center
+                    };
+            }
+        }
+
         /// <summary>
         /// Computes the <see cref="OrientedBoundingRectangle"/> from the specified <paramref name="rectangle"/>
         /// transformed by <paramref name="transformMatrix"/>.
@@ -62,7 +85,6 @@ namespace MonoGame.Extended
         {
             PrimitivesHelper.TransformOrientedBoundingRectangle(
                 ref rectangle.Center,
-                ref rectangle.Radii,
                 ref rectangle.Orientation,
                 ref transformMatrix);
             result.Center = rectangle.Center;
@@ -127,6 +149,14 @@ namespace MonoGame.Extended
             return HashCode.Combine(Center, Radii, Orientation);
         }
 
+        public static explicit operator OrientedBoundingRectangle(RectangleF rectangle)
+        {
+            var radii = new Size2(rectangle.Width * 0.5f, rectangle.Height * 0.5f);
+            var centre = new Point2(rectangle.X + radii.Width, rectangle.Y + radii.Height);
+
+            return new OrientedBoundingRectangle(centre, radii, Matrix2.Identity);
+        }
+
         /// <summary>
         /// Returns a <see cref="string" /> that represents this <see cref="OrientedBoundingRectangle" />.
         /// </summary>

src/cs/MonoGame.Extended/Math/PrimitivesHelper.cs

@@ -74,17 +74,12 @@ namespace MonoGame.Extended
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static void TransformOrientedBoundingRectangle(
             ref Point2 center,
-            ref Vector2 radii,
             ref Matrix2 orientation,
             ref Matrix2 transformMatrix)
         {
             // Real-Time Collision Detection, Christer Ericson, 2005. Chapter 4.4; Oriented Bounding Boxes (OBBs), pg 101-105.
 
             center = transformMatrix.Transform(center);
-            var xRadius = radii.X;
-            var yRadius = radii.Y;
-            radii.X = xRadius * Math.Abs(transformMatrix.M11) + yRadius * Math.Abs(transformMatrix.M12);
-            radii.Y = xRadius * Math.Abs(transformMatrix.M21) + yRadius * Math.Abs(transformMatrix.M22);
             orientation *= transformMatrix;
             // Reset the translation since orientation is only about rotation
             orientation.M31 = 0;

src/cs/Tests/MonoGame.Extended.Tests/CollectionAssert.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using Xunit;
+
+namespace MonoGame.Extended.Tests;
+
+public static class CollectionAssert
+{
+    public static void Equal<T>(IReadOnlyList<T> expected, IReadOnlyList<T> actual)
+    {
+        Assert.True(expected.Count == actual.Count, "The number of items in the collections does not match.");
+
+        Assert.All(actual, x => Assert.Contains(x, expected));
+    }
+}

src/cs/Tests/MonoGame.Extended.Tests/Primitives/OrientedBoundingRectangleTests.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Numerics;
 using Microsoft.Xna.Framework;
 using Xunit;
 using Vector2 = Microsoft.Xna.Framework.Vector2;
@@ -11,11 +10,20 @@ public class OrientedBoundingRectangleTests
     [Fact]
     public void Initializes_oriented_bounding_rectangle()
     {
-        var rect = new OrientedBoundingRectangle(new Point2(1, 2), new Size2(3, 4), new Matrix2(5, 6, 7, 8, 9, 10));
+        var rectangle = new OrientedBoundingRectangle(new Point2(1, 2), new Size2(3, 4), new Matrix2(5, 6, 7, 8, 9, 10));
 
-        Assert.Equal(new Point2(1, 2), rect.Center);
-        Assert.Equal(new Vector2(3, 4), rect.Radii);
-        Assert.Equal(new Matrix2(5, 6, 7, 8, 9, 10), rect.Orientation);
+        Assert.Equal(new Point2(1, 2), rectangle.Center);
+        Assert.Equal(new Vector2(3, 4), rectangle.Radii);
+        Assert.Equal(new Matrix2(5, 6, 7, 8, 9, 10), rectangle.Orientation);
+        CollectionAssert.Equal(
+            new List<Vector2>
+                {
+                    new(-3, -2),
+                    new(-33, -38),
+                    new(23, 26),
+                    new(53, 62)
+                },
+            rectangle.Points);
     }
 
     public static readonly IEnumerable<object[]> _equalsComparisons = new[]
@@ -49,7 +57,7 @@ public class OrientedBoundingRectangleTests
         [Fact]
         public void Center_point_is_not_translated()
         {
-            var rectangle = new OrientedBoundingRectangle(new Point2(1, 2), new Size2(), new Matrix2());
+            var rectangle = new OrientedBoundingRectangle(new Point2(1, 2), new Size2(), Matrix2.Identity);
             var transform = Matrix2.Identity;
 
             var result = OrientedBoundingRectangle.Transform(rectangle, ref transform);
@@ -91,7 +99,7 @@ public class OrientedBoundingRectangleTests
         }
 
         [Fact]
-        public void Rotate_45_degrees_left()
+        public void Orientation_is_rotated_45_degrees_left()
         {
             var rectangle = new OrientedBoundingRectangle(new Point2(), new Size2(), Matrix2.Identity);
             var transform = Matrix2.CreateRotationZ(MathHelper.PiOver4);
@@ -104,7 +112,7 @@ public class OrientedBoundingRectangleTests
         }
 
         [Fact]
-        public void Rotate_to_45_degrees_from_180()
+        public void Orientation_is_rotated_to_45_degrees_from_180()
         {
             var rectangle = new OrientedBoundingRectangle(new Point2(), new Size2(), Matrix2.CreateRotationZ(MathHelper.Pi));
             var transform = Matrix2.CreateRotationZ(-3 * MathHelper.PiOver4);
@@ -122,6 +130,44 @@ public class OrientedBoundingRectangleTests
             Assert.Equal(expectedOrientation.M32, result.Orientation.M32, 6);
         }
 
+        [Fact]
+        public void Points_are_same_as_center()
+        {
+            var rectangle = new OrientedBoundingRectangle(new Point2(1, 2), new Size2(), Matrix2.Identity);
+            var transform = Matrix2.Identity;
+
+            var result = OrientedBoundingRectangle.Transform(rectangle, ref transform);
+
+            CollectionAssert.Equal(
+                new List<Vector2>
+                    {
+                        new(1, 2),
+                        new(1, 2),
+                        new(1, 2),
+                        new(1, 2)
+                    },
+                result.Points);
+        }
+
+        [Fact]
+        public void Points_are_translated()
+        {
+            var rectangle = new OrientedBoundingRectangle(new Point2(0, 0), new Size2(2, 4), Matrix2.Identity);
+            var transform = Matrix2.CreateTranslation(10, 20);
+
+            var result = OrientedBoundingRectangle.Transform(rectangle, ref transform);
+
+            CollectionAssert.Equal(
+                new List<Vector2>
+                    {
+                        new(8, 16),
+                        new(8, 24),
+                        new(12, 24),
+                        new(12, 16)
+                    },
+                result.Points);
+        }
+
         [Fact]
         public void Applies_rotation_and_translation()
         {
@@ -169,11 +215,20 @@ public class OrientedBoundingRectangleTests
 
             var result = OrientedBoundingRectangle.Transform(rectangle, ref transform);
 
-            Assert.Equal(-2 + 10, result.Center.X, 6);
-            Assert.Equal(1 + 20, result.Center.Y, 6);
-            Assert.Equal(4, result.Radii.X, 6);
-            Assert.Equal(2, result.Radii.Y, 6);
+            Assert.Equal(8, result.Center.X, 6);
+            Assert.Equal(21, result.Center.Y, 6);
+            Assert.Equal(2, result.Radii.X, 6);
+            Assert.Equal(4, result.Radii.Y, 6);
             Assert.Equal(Matrix2.CreateRotationZ(MathHelper.PiOver2), result.Orientation);
+            CollectionAssert.Equal(
+                new List<Vector2>
+                    {
+                        new(4, 23),
+                        new(4, 19),
+                        new(12, 19),
+                        new(12, 23)
+                    },
+                result.Points);
         }
     }
 }