- Improve from stackalloc to Unsafe to use pointers

Author: Jorgemagic

MeshOptimizerGen/HelloMeshlets/Program.cs

@@ -6,6 +6,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 namespace HelloMeshlets
@@ -57,31 +58,31 @@ public unsafe static void Main(string[] args)
             byte[] meshletTriangles = new byte[maxMeshlets * kMaxTriangles * 3];
             Vector3[] positions = attrib.Vertices.ToArray();
 
-            fixed (meshopt_Meshlet* pMeshlets = &meshlets[0])
-            fixed (uint* pMeshletVertices = &meshletVertices[0])
-            fixed (byte* pMeshletTriangles = &meshletTriangles[0])
-            fixed (uint* pIndices = &indices[0])
-            fixed (Vector3* pPositions = &positions[0])
-            {
-                float* pVertsAsFloats = (float*)pPositions;
-
-                uint meshletCount = MeshOptNative.meshopt_buildMeshlets(
-                                                                        pMeshlets,
-                                                                        pMeshletVertices,
-                                                                        pMeshletTriangles,
-                                                                        pIndices,
-                                                                        meshNumIndices,
-                                                                        pVertsAsFloats,
-                                                                        meshNumVertices,
-                                                                        (uint)sizeof(Vector3),
-                                                                        kMaxVertices,
-                                                                        kMaxTriangles,
-                                                                        kConeWeight);
+            meshopt_Meshlet* pMeshlets = (meshopt_Meshlet*)Unsafe.AsPointer(ref MemoryMarshal.GetArrayDataReference(meshlets));
+            uint* pMeshletVertices = (uint*)Unsafe.AsPointer(ref MemoryMarshal.GetArrayDataReference(meshletVertices));
+            byte* pMeshletTriangles = (byte*)Unsafe.AsPointer(ref MemoryMarshal.GetArrayDataReference(meshletTriangles));
+            uint* pIndices = (uint*)Unsafe.AsPointer(ref MemoryMarshal.GetArrayDataReference(indices));
+            float* pVertsAsFloats = (float*)Unsafe.AsPointer(ref MemoryMarshal.GetArrayDataReference(positions));
 
-                Console.WriteLine($"{meshletCount} meshlets generated");
-            }
+            uint meshletCount = MeshOptNative.meshopt_buildMeshlets(
+                                                                    pMeshlets,
+                                                                    pMeshletVertices,
+                                                                    pMeshletTriangles,
+                                                                    pIndices,
+                                                                    meshNumIndices,
+                                                                    pVertsAsFloats,
+                                                                    meshNumVertices,
+                                                                    (uint)sizeof(Vector3),
+                                                                    kMaxVertices,
+                                                                    kMaxTriangles,
+                                                                    kConeWeight);
 
+            var last = meshlets[meshletCount - 1];
+            Array.Resize(ref meshletVertices, (int)(last.vertex_offset + last.vertex_count));
+            Array.Resize(ref meshletTriangles, (int)(last.triangle_offset + ((last.triangle_count * 3 + 3) & ~3)));
+            Array.Resize(ref meshlets, (int)meshletCount);            
 
+            Console.WriteLine($"{meshletCount} meshlets generated");
         }
 
         private static IntPtr ResolveRuntimes(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)