From ab2c5200768847b0aeca47e3803464c34e2f570e Mon Sep 17 00:00:00 2001
From: ikpil <ikpil@naver.com>
Date: Fri, 5 Jul 2024 00:15:03 +0900
Subject: [PATCH] Changed `new float[]` to `stackalloc float[]` in
 `DtConvexConvexIntersections.Intersect()`

---
 CHANGELOG.md                                  |  1 +
 .../DtConvexConvexIntersections.cs            | 14 +++----
 .../DtStrictDtPolygonByCircleConstraint.cs    | 38 +++++++++----------
 3 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9de7fcd..a83a32f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Changed stack handling from List to a fixed-size array with manual index management for optimization in `RcLayers.BuildHeightfieldLayers()`
 - Changed to use Span<byte> and stackalloc for improved performance and memory management in `RcLayers.BuildHeightfieldLayers()`
 - Changed vertCount and triCount to byte in `DtPolyDetail`
+- Changed `new float[]` to `stackalloc float[]` in `DtConvexConvexIntersections.Intersect()`
 
 ### Removed
 - Removed RcMeshDetails.VdistSq2(float[], float[])
diff --git a/src/DotRecast.Detour/DtConvexConvexIntersections.cs b/src/DotRecast.Detour/DtConvexConvexIntersections.cs
index 7537679..4e219ee 100644
--- a/src/DotRecast.Detour/DtConvexConvexIntersections.cs
+++ b/src/DotRecast.Detour/DtConvexConvexIntersections.cs
@@ -18,23 +18,20 @@ freely, subject to the following restrictions:
 */
 
 using System;
-using DotRecast.Core;
 using DotRecast.Core.Numerics;
 
 namespace DotRecast.Detour
 {
-    /**
- * Convex-convex intersection based on "Computational Geometry in C" by Joseph O'Rourke
- */
+    // Convex-convex intersection based on "Computational Geometry in C" by Joseph O'Rourke
     public static class DtConvexConvexIntersections
     {
         private const float EPSILON = 0.0001f;
 
-        public static float[] Intersect(float[] p, float[] q)
+        public static float[] Intersect(Span<float> p, Span<float> q)
         {
             int n = p.Length / 3;
             int m = q.Length / 3;
-            float[] inters = new float[Math.Max(m, n) * 3 * 3];
+            Span<float> inters = stackalloc float[Math.Max(m, n) * 3 * 3];
             int ii = 0;
             /* Initialize variables. */
             RcVec3f a = new RcVec3f();
@@ -171,12 +168,11 @@ namespace DotRecast.Detour
                 return null;
             }
 
-            float[] copied = new float[ii];
-            RcArrays.Copy(inters, copied, ii);
+            float[] copied = inters.Slice(0, ii).ToArray();
             return copied;
         }
 
-        private static int AddVertex(float[] inters, int ii, RcVec3f p)
+        private static int AddVertex(Span<float> inters, int ii, RcVec3f p)
         {
             if (ii > 0)
             {
diff --git a/src/DotRecast.Detour/DtStrictDtPolygonByCircleConstraint.cs b/src/DotRecast.Detour/DtStrictDtPolygonByCircleConstraint.cs
index 1c78b6e..4e94b91 100644
--- a/src/DotRecast.Detour/DtStrictDtPolygonByCircleConstraint.cs
+++ b/src/DotRecast.Detour/DtStrictDtPolygonByCircleConstraint.cs
@@ -3,13 +3,11 @@ using DotRecast.Core.Numerics;
 
 namespace DotRecast.Detour
 {
-    /**
-     * Calculate the intersection between a polygon and a circle. A dodecagon is used as an approximation of the circle.
-     */
+    // Calculate the intersection between a polygon and a circle. A dodecagon is used as an approximation of the circle.
     public class DtStrictDtPolygonByCircleConstraint : IDtPolygonByCircleConstraint
     {
         private const int CIRCLE_SEGMENTS = 12;
-        private static readonly float[] UnitCircle = MakeUnitCircle();
+        private static readonly float[] UnitCircle = CreateCircle();
 
         public static readonly IDtPolygonByCircleConstraint Shared = new DtStrictDtPolygonByCircleConstraint();
 
@@ -17,7 +15,7 @@ namespace DotRecast.Detour
         {
         }
 
-        private static float[] MakeUnitCircle()
+        public static float[] CreateCircle()
         {
             var temp = new float[CIRCLE_SEGMENTS * 3];
             for (int i = 0; i < CIRCLE_SEGMENTS; i++)
@@ -31,6 +29,17 @@ namespace DotRecast.Detour
             return temp;
         }
 
+        public static void ScaleCircle(Span<float> src, RcVec3f center, float radius, Span<float> dst)
+        {
+            for (int i = 0; i < CIRCLE_SEGMENTS; i++)
+            {
+                dst[3 * i] = src[3 * i] * radius + center.X;
+                dst[3 * i + 1] = center.Y;
+                dst[3 * i + 2] = src[3 * i + 2] * radius + center.Z;
+            }
+        }
+
+
         public float[] Apply(float[] verts, RcVec3f center, float radius)
         {
             float radiusSqr = radius * radius;
@@ -50,29 +59,16 @@ namespace DotRecast.Detour
                 return verts;
             }
 
-            float[] qCircle = Circle(center, radius);
+            Span<float> qCircle = stackalloc float[UnitCircle.Length];
+            ScaleCircle(UnitCircle, center, radius, qCircle);
             float[] intersection = DtConvexConvexIntersections.Intersect(verts, qCircle);
             if (intersection == null && DtUtils.PointInPolygon(center, verts, verts.Length / 3))
             {
                 // circle inside polygon
-                return qCircle;
+                return qCircle.ToArray();
             }
 
             return intersection;
         }
-
-
-        private float[] Circle(RcVec3f center, float radius)
-        {
-            float[] circle = new float[12 * 3];
-            for (int i = 0; i < CIRCLE_SEGMENTS * 3; i += 3)
-            {
-                circle[i] = UnitCircle[i] * radius + center.X;
-                circle[i + 1] = center.Y;
-                circle[i + 2] = UnitCircle[i + 2] * radius + center.Z;
-            }
-
-            return circle;
-        }
     }
 }
\ No newline at end of file